IMPROVING VERTICAL JUMP PERFORMANCE WITH

IMPROVING VERTICAL JUMP PERFORMANCE WITH

BIOMECHANICAL FEEDBACK

____________

A Thesis

Presented

to the Faculty of

California State University, Chico

____________

In Partial Fulfillment

of the Requirements for the Degree

Master of Arts

in

Kinesiology

____________

by

Paula T. García Krauss

Spring 2017



A Thesis

by


Spring 2017

APPROVED BY THE INTERIM DEAN OF GRADUATE STUDIES:

_________________________________ Sharon Barrios, Ph.D.

APPROVED BY THE GRADUATE ADVISORY COMMITTEE:

_________________________________ _________________________________ Kevin G. Patton, Ed.D. Melissa A. Mache, Ph.D., Chair Graduate Coordinator

_________________________________ ChengTu Hsieh, Ph.D.

iii

DEDICATION

To Lucas because your excitement and beautiful giant smile every time you

see me is the highlight of my day, for showing me that love has no limit and that

sometimes all we need is a hug. Das los mejores abrazos vida mía. Gracias por comerte

todas las cosas verdes que mamá te alimenta, porque así tienes músculos grandes para

dar esos abrazos apretados apretados. Te amo.

To the baby inside my belly for the kicks and the excitement of expecting a

new baby AND a girl. I can’t wait to hold you and kiss you!

iv

ACKNOWLEDGMENTS

Dr. Mache, your invaluable help throughout this process made this thesis not

only possible but so much better than it would have been. There are no words to describe

how much I appreciate your patience with my writing skills and lack of time, as well as

your willingness to sacrifice your free time and run to my help. Your gentle guidance,

attention to detail, and timely instigation helped me stayed on task (most of the time) and

inspired me to finish. Thank you so much! There is no way I could have done this

without you.

Dr. Hsieh, thank you so much being part of my thesis committee. Your

feedback made my thesis much better and I am very grateful for your time and energy.

Dr. Patton, thank you for being a great professor. You are not only a splendid

teacher but a role model for us Physical educators. Thank you so much for taking the

time to read my thesis and providing insight regarding the practicality of these findings to

us PE teachers.

To my sister, for gently hinting “how is your thesis going?” without actually

asking the question. For your continuous encouragement and endless support. You are

my rock and my best friend, and without our daily talks or chats I would be lost in life.

To my family, for believing in my abilities and for teaching me that we must

work hard for what we want. To mom and dad, for showing me with the best example

that for the good energy we put in, life will give back much more. For teaching me how

to be courteous to everyone and to never give up. I love you guys!

v

TABLE OF CONTENTS

PAGE

Dedication................................................................................................................... iii Acknowledgments ...................................................................................................... iv List of Tables.............................................................................................................. vii Abstract....................................................................................................................... viii

CHAPTER I. Introduction .............................................................................................. 1

Statement of the Problem ............................................................. 5 Hypotheses ................................................................................... 6 Purpose of the Study..................................................................... 6 Limitations.................................................................................... 7 Definition of Terms ...................................................................... 8

II. Review of Literature................................................................................. 11

Skillful Jumping ........................................................................... 11 Biomechanics of the Vertical Jump.............................................. 12 Training Methods for Improving Vertical Jump Height .............. 19 Feedback to Enhance Skill ........................................................... 23 The Use of Technology for Enhancing Movement ...................... 29 Summary....................................................................................... 30

III. Methods .................................................................................................... 31

Participants ................................................................................... 31 Testing .......................................................................................... 32 Data Collection Protocol .............................................................. 38 Data Analysis and Calculations.................................................... 39

vi

CHAPTER PAGE

IV. Manuscript ................................................................................................ 41

Abstract......................................................................................... 41 Introduction .................................................................................. 42 Methods ........................................................................................ 44 Data Collection Protocol .............................................................. 47 Data Analysis and Calculations.................................................... 48 Results .......................................................................................... 50 Discussion..................................................................................... 52 Conclusions .................................................................................. 64 References .................................................................................... 65

References .................................................................................................................. 69

Appendices A. Informed Consent for Participation in Research ...................................... 75 B. Data Collection Form ............................................................................... 77 C. Dynamic Warm-Up Exercises.................................................................. 80 D. Participant Jump Performance Scale ........................................................ 82 E. Knee Flexion (°), Depth of Descent (cm), and Jump Height (cm)

Data for All Participants and for Pre-and-Post-Feedback Jumps....... 84

vii

LIST OF TABLES

TABLE PAGE 1. Visual and Verbal Feedback Provided to Control and

Treatment Groups............................................................................... 46 2. Participant Numbers by Group and Feedback Condition Based

on Pre-Feedback Knee Flexion Angles .............................................. 50 3. Knee Flexion Angles (°) for Under the Target Zone Treatment

Group Participants .............................................................................. 50 4. Depth of Descent (cm) for Under the Target Zone Treatment

Group Participants .............................................................................. 51 5. Jump Height (cm) for Under the Target Zone Treatment Group

Participants ......................................................................................... 51 6. Knee Flexion (°), Depth of Descent (cm), and Jump

Height (cm) Means (±SD) During Pre-feedback Maximal Vertical Jumps .................................................................................... 51

7. Knee Flexion (°), Depth of Descent (cm), and Jump

Height (cm) Means (±SD) During Post-feedback Maximal Vertical Jumps .................................................................................... 52

viii

ABSTRACT



by


Master of Arts in Kinesiology

California State University, Chico

Spring 2017

The vertical jump is a skill fundamental to many sports and one for which

improvements in performance result in a greater chance of success in a competitive

setting. Unfortunately, there is limited research related to the use of specific visual and

verbal feedback and based on the knowledge of the biomechanics of skillful jumping.

The purpose of this study was to investigate the use of specific biomechanical feedback

to improve vertical jump performance in recreationally active women.

Twenty women were randomly assigned to the treatment or control group.

Participants performed five maximal countermovement jumps with arms akimbo pre-

feedback and five jumps post-feedback. Specific visual and verbal feedback based on the

mover’s pre-feedback jumps was provided to the treatment group, while control

participants were allowed to view their jump performance on video only.

ix

Treatment participants made significant reductions in maximal knee flexion

angle pre- to post-feedback (p=0.003); however no changes in knee flexion were

observed among control participants (p=0.667). Depth of descent decreased significantly

from pre- to post-feedback among treatment and control participants (p=0.003). However

observed changes in range of motion occurred in the absence of improvements in jump

height (p=0.07). Present findings suggest specific visual and verbal feedback is an

effective means of modifying movement patterns, however, the knee flexion feedback in

the present study was not suitable for improving vertical jump height. Researchers

should continue to explore suitable visual and verbal feedback for modifying movement

and improving vertical jump performance.

1

CHAPTER I

INTRODUCTION

At all levels of competition in sport coaches try to help their athletes improve

performance, one method of doing this is by providing athletes with feedback. The

current study focuses on the use of such feedback to help individuals improve their

performance of a skill important to many sports: vertical jumping. Because vertical

jumping is important for success in so many sports (e.g., jumping to grab a rebound in

basketball or to execute an overhead hit in volleyball) coaches and athletes alike are

constantly searching for means of increasing maximal vertical jump height in order to

gain an advantage over their competitors.

In an effort to better understand factors that may contribute to greater vertical

jump height researchers have exhaustively examined the biomechanics of the vertical

jump. Most of these biomechanical studies have focused their attention on analyzing the

vertical jump from a correlational or descriptive point of view (Aragon-Vargas & Gross,

1997a; Hsieh & Cheng, 2016; Hudson, 1990). This has provided extensive information

related to the biomechanics of skilled jumping, however, these studies do not provide

much information on how to assist a less skilled jumper in improving their vertical jump

height. Other researchers have used comparative methods to highlight differences

between more and less skilled jumpers (Hsieh & Cheng, 2016; Hudson & Owen, 1982;

Hudson & Wilkerson, 1987). Together, these descriptive and comparative studies have

2

identified several variables that may be crucial to vertical jump performance, including

range of motion.

Range of motion in the vertical jump has been measured in a variety of ways;

two of these methods are particularly relevant to the present study: The maximum knee

flexion angle during the vertical jump has been studied as a means of understanding the

range of motion of a section of the body; and depth of descent has been studied to

understand range of motion at a more somatic (i.e., whole-body) level. Diverse values

have been reported for range of motion in the countermovement of the vertical jump

(Gelpi, 1997; Hudson & Owen, 1982; Knudson & Miller, 1997; Mache, 2005; Ross &

Hudson, 1997). Despite the wide range of previously reported values for maximum knee

flexion during the descent phase of the countermovement jump, knee range of motion is

thought to have a significant effect on jump height (Domire & Challis, 2007; Hsieh &

Cheng, 2016; Ross & Hudson, 1997). Some researchers have reported that skilled

jumpers use a smaller range of motion than less skilled jumpers (Hudson & Owen, 1982);

whereas other research indicates that skilled jumpers may use a larger range of motion

than less skilled jumpers (Hsieh & Cheng, 2016). Though we have extensive descriptions

of the biomechanics of skillful jumping, at present, direct application of this knowledge is

lacking.

Often rather than focusing on improving jumping skill directly, researchers,

coaches, and athletes have used more indirect means to attempt to improve vertical jump

performance; individuals have developed methods such as strength training programs and

plyometric exercises aimed at increasing vertical jump height. These approaches for

attempting to improve vertical jump performance have had mixed results. Bobbert and

3

Van Soest (1994) sought to enhance vertical jump performance by using strength training

methods but their results showed that increases in strength did not lead to improvements

in vertical jump height. These findings are in agreement with the work of other

researchers who have shown weak associations between leg strength and vertical jump

performance (Aragon-Vargas & Gross, 1997a; Tomioka, Owings, & Grabiner, 2001).

Furthermore, analysis of vertical jump force-time and power-time curves has led some to

conclude that strength alone is not enough to ensure improvements in vertical jump

height (Dowling & Vamos, 1993). In contrast to the evidence regarding strength training

and vertical jump height, plyometric training programs ranging from six to eight weeks in

duration have consistently been shown to be associated with improvements in vertical

jump height (Makaruk, Czaplicki, Sacewicz, & Sadowski, 2014; Miller, 1982). With

careful implementation it appears that some training methods aimed at improving vertical

jump performance can be effective; however, the physiological adaptations necessary for

these methods to have the chance to be effective are often time consuming.

Providing jumpers with specific feedback based on the jumper’s performance

and our extensive knowledge of the biomechanics of skilled vertical jumping may be a

more immediate and efficient method of eliciting improvements in vertical jump height.

Specifically it may be helpful to give a jumper augmented feedback (i.e., provide the

individual with information to supplement what is naturally available to them) to help

them jump higher (Onate, Guskiewicz, Marshall, Giuliani, Yu, & Garrett, 2005). In order

for this augmented feedback to be effective it is likely that the feedback must focus on a

direct and measurable aspects of the task rather than the outcome of the task (Staub et al.

2013). Providing visual and verbal feedback may be a viable mean of using existing

4

biomechanical knowledge of skilled vertical jumping to elicit improvements in vertical

jump performance.

The efficacy of augmented feedback for modifying vertical jump performance

has been previously demonstrated by Keller, Lauber, Gehring, Leukel, and Taube (2014)

and Staub et al. (2013) and in a couple of unpublished studies (Gelpi, 1997; Mache,

2005). Specifically, Keller et al. (2014) found that augmented feedback resulted in

immediate increases in jump height (i.e., within a single feedback session). Similarly,

Gelpi (1997) and Mache (2005) used the knowledge of range of motion as it relates to

skill in the vertical jump in an attempt to improve vertical jump performance. Gelpi

(1997) used a pre-experimental design and non-specific verbal feedback in an attempt to

get jumpers to use a smaller range of motion with the belief that this would result in

increased maximal vertical jump height. This non-specific feedback resulted in

improvements in vertical jump height for some jumpers whereas other jumpers actually

exhibited a decrease in jump height. In a similar study, Mache (2005) provided specific

visual and verbal feedback aimed at modifying range of motion in the vertical jump and

improving vertical jump height. Mache (2005) was able to demonstrate that specific

visual and verbal feedback was effective in modifying range of motion and improving

vertical jump height. Since the study of Mache (2005) was conducted biomechanical

instrumentation has improved (i.e., two-dimensional versus three-dimensional motion

capture methods). Furthermore, video has become ubiquitous with the advent of tablets

(e.g., the iPad) and smartphones making it much easier for the average coach to have the

ability to provide visual feedback to their athletes.

5

The results of previous studies seem to indicate that providing visual and

verbal feedback are effective means of modifying movement, specifically in the vertical

jump (Gelpi, 1997; Keller et al., 2014; Mache, 2005). The use of augmented feedback is

particularly exciting as athletes could potentially see immediate improvements in the

performance of vertical jumping with the incorporation of appropriate feedback. The

previously discussed studies are the only ones known to have used visual and verbal

feedback with the objective of improving vertical jump height. In order to test the

efficacy of biomechanical feedback to improve performance, a true experimental study

design is necessary. Furthermore, such a study should incorporate the use of current

technology (i.e., three-dimensional motion analysis and iPad video). Therefore, the

present study will involve providing augmented feedback to jumpers based on the

knowledge of the biomechanics of skilled jumpers, and the specific performance of the

jumper, using technology readily available to the everyday coach (i.e., the iPad). This

will enable the researcher to test the hypotheses that participants can incorporate visual

and verbal feedback to modify the kinematics of the jumping motion and increase vertical

jump height.

Statement of the Problem

The present investigator examined whether the use of visual and verbal

biomechanical feedback is an effective means of improving vertical jump performance in

recreationally active college-aged women. The current study had two primary objectives:

(1) Examine the effect of biomechanical feedback on the kinematics of the vertical

6

jumping motion, and (2) examine the effect of biomechanical feedback on maximal

vertical jump height.

Hypotheses

1. Participants would be able to incorporate the visual and verbal feedback,

resulting in biomechanical alterations during the jumping motion.

a. Treatment participants would be able to alter knee flexion in a way that

corresponds with the specific feedback that they were provided.

b. Participants who were asked to alter knee flexion would show

corresponding changes in their depth of descent during the jump.

2. Participants who were given specific visual and verbal feedback would be

able to jump higher when incorporating the feedback given.

3. Participants who were not given specific feedback would not change their

jumping mechanics in a way that would result in increased vertical jump height.

Purpose of the Study

Previous biomechanical research related to the vertical jump has been

primarily limited to descriptive, correlational, comparative, and pre-experimental study

designs. It is imperative to take the information regarding the biomechanics of skillful

vertical jumping that has been accumulated by researchers and make it useful to coaches

and athletes at all levels of sport. That is, we must synthesize what we know about

skillful movement and begin to develop means of making this information applicable to

eliciting more skillful movement. It may be that visual and verbal biomechanical

7

feedback will be an effective way to make existing biomechanical knowledge useful to a

broader audience (e.g., coaches, athletes, athletic trainers, etc.).

Information on whether or not feedback alone can improve jumping height in

active women would allow coaches and teachers to make evidence-based decisions about

which feedback modalities to include in their training programs. It could also help them

to make informed decisions based on cost (i.e., time, equipment, personnel, etc.). If

feedback is determined to be an effective means of improving vertical jump performance,

then feedback may become a valuable method of using our existing biomechanical

knowledge of skillful movement to improve the skill level of movers of all abilities in a

wide variety of movement tasks.

Limitations

The limitations of the study were as follows:

1. Only one jump per participant was chosen to provide feedback. However, the

researcher is confident that this was an effective strategy as the criteria that were used in

this study to select a jump for the purposes of feedback had been successfully used in

previous research (Mache, 2005). In addition, the reliability of kinematic variables in the

vertical jump has been previously established (Hudson, 1986).

2. Despite having clear inclusion criteria for this study, the population of

participants represented range of physical activity levels and jumping experience.

However, the researcher is confident that the level of physical activity required to

participate in this study minimized any potential effects of the varying levels of physical

activity and jumping experience among study participants.

8

3. As is the case with any study of this nature, the inclusion criteria (e.g., age and

physical activity level) will only allow the researcher to generalize the results of this

study to other individuals who match the inclusion criteria of this study.

4. Sample size was small. However, the sample size was similar to sample sizes

used in previous work (Aragon-Vargas & Gross, 1997b; Mache, 2005)

5. The time participants had to practice and incorporate verbal and visual

feedback was relatively short and may have precluded some participants from feeling

fully comfortable with the task. However, every effort was made to allow participants

enough time to attempt to incorporate the provided feedback within the testing session.

Furthermore, similar methods for providing feedback have been successfully used in

previous research (Mache, 2005).

Definition of Terms

Augmented Feedback

Augmented feedback is external information about the motor task that

supplements the naturally available information (Prapavessis & McNair, 1999).

Biomechanics

The area of science that involves the application of mechanical principles to

biological problems (Whiting & Zernicke, 1998).

Center of Mass (COM)

The point at which the entire mass of a body may be considered as

concentrated so that if supported at this point the body would remain in equilibrium in

any position (“Center of Mass,” n.d.).

9

Core Concepts of Biomechanics

Concepts that are the basis of communication regarding movement and

facilitate the development of skilled performance (Hudson, 1995).

Counter Movement Jump (CMJ)

A jump starting from an erect standing posture, from this position the

individual initiates a preparatory downward motion that is immediately followed by an

upward thrust of the body (Hudson & Owen, 1982).

Depth of Descent

Distance the body’s center of gravity travels from an upright standing position

to the lowest position in the preparatory phase of the vertical jump; it represents the

amount by which the body’s center of gravity is lowered in the counter movement of the

jump.

Hudl Technique App

A free software application, formerly known as Ubersense, that can be

downloaded to a mobile device, such as the iPad2. This application allows the user to

record and analyze movement in slow motion.

Jump Height

The difference between peak height of the center of mass during the airborne

phase of the vertical jump and the height of the center of mass at takeoff.

Kinematics

Branch of dynamics that deals with aspects of motion apart from

considerations of mass and force (“Kinematics,” n.d.).

10

Knee Angle at Full Crouch

The angle in degrees of greatest knee flexion during the vertical jump. Greater

angles indicate greater flexion and a larger range of motion during the countermovement

of the jump.

iPad2

Line of tablet computers designed and marketed by Apple Inc. An iPad can

shoot video, take photos, play music, and perform Internet functions such as web-

browsing and emailing.

Range of Motion

Range of motion is defined as the distance that a body, a body part, or an

object moves during a time interval of interest (Hudson, 1995).

Takeoff

The instant in which the participant’s body becomes airborne, this instant will

be identified by a ground reaction force less than 10 Newtons.

11

CHAPTER II

REVIEW OF LITERATURE

The purpose of this study was to investigate whether the use of biomechanical

feedback improves vertical jump performance in recreationally active college-aged

women. The first objective was to examine the effect of biomechanical feedback on the

kinematics of the vertical jumping motion. The second objective was to examine the

effect of biomechanical feedback on maximal vertical jump height.

Skillful Jumping

Hudson (1990) described the vertical jump by identifying three key events

during the jumping motion, she suggested the phrase “drop, stop, and pop” to describe

these events. The “drop” is characterized by the body moving downward rapidly during

which time flexion of the hip, knee, and ankle occur. According to Hudson (1990) skilled

jumpers take a small drop, indicating that a moderate range of motion is desired for a

successful jump. The “stop” happens when the athlete vigorously activates the muscles

eccentrically and the downward movement is stopped briefly. Skilled jumpers are also

known for a very abrupt stop, that is the trunk, thighs, and shanks cease their downward

movement at nearly the exact same time (Hudson, 1990). In the “pop,” the muscles of the

legs and back quickly and forcefully shorten causing extension of the hip, knee, and

ankle, resulting in a very quick upward motion in skilled jumpers. It is this quick motion

12

that eventually leads to takeoff of the jumper and the subsequent flight phase of the

vertical jump.

Hudson (1990) described five additional characteristics of jumpers who are

able to skillfully achieve the “drop, stop, and pop”: (a) they move all the appropriate

body parts (i.e., trunk, thighs, shanks, and arms) vigorously; (b) they maintain proper

balance throughout the jump; (c) they have a shallower rather than a deeper drop (i.e.

crouch); (d) they have a quick pop; and (e) they exhibit a simultaneous coordination of

body segments during the jumping motion.

Biomechanics of the Vertical Jump

Biomechanists have used a variety of approaches, including descriptive,

correlational, and comparative methods, in an attempt to understand the biomechanics of

a skillful maximal vertical jump. In evaluating the kinematics of jumping, variables such

as joint range of motion, velocity, and the position of the center of mass at takeoff have

been described as critical to the skillful performance of a vertical jump (Aragon-Vargas

& Gross, 1997a; Bobbert & Van Ingen Schenau, 1988). For example, Aragon-Vargas and

Gross (1997a) used a correlational study to demonstrate that the position and velocity of

the body’s center of mass (COM) at takeoff accounts for 95% of the variation in vertical

jump height. These results are in accordance with the previous findings of Bobbert and

Van Ingen Schenau (1988) who stated that vertical jump height improves with the

optimization of both the height of the body’s COM and the vertical velocity of the COM

at the instant of takeoff. In order to optimize both the COM’s velocity and position at

13

takeoff, to maximize vertical jump height, it may be important to examine variables

associated with the process of the vertical jump, such as range of motion.

Range of Motion

Range of motion can be defined as the distance that a body, a body segment,

or an object moves during a time interval of interest (Hudson, 1995). Researchers have

taken a variety of approaches when measuring range of motion during the vertical jump.

While studying the range of motion of a section of the body during the vertical jump

researchers often choose to examine the maximum knee flexion angle during the

countermovement of the jumping motion. Other researchers have chosen to evaluate the

range of motion of the entire body by measuring the change in vertical position of the

body’s COM during the jumping motion (i.e., depth of descent).

Because range of motion is a process variable of the vertical jump that has

been previously shown to account for differences in jump height, it will be taken into

consideration in the present study (Hsieh & Cheng, 2016; Hudson & Owen, 1985;

Mache, 2005; Ross & Hudson, 1997). The following narrative will provide information

regarding the relationship between range of motion and vertical jump performance. This

discussion will include an examination of range of motion as measured by the maximal

knee flexion angle and depth of descent, two common means of assessing range of

motion during the vertical jump.

Knee Flexion Angle. Maximal knee flexion angle during the

countermovement of the vertical jump has been previously shown to have a significant

effect on vertical jump performance (Domire & Challis, 2007; Hsieh & Cheng, 2016).

Hence, knee flexion in jumping has been studied extensively by biomechanists. This

14

research has resulted in a set of commonly reported values for maximum knee flexion

between 74° and 110° in the vertical jump, where larger values indicate greater knee

flexion (Domire & Challis, 2007; Hsieh & Cheng, 2016; Hudson & Owen, 1982; Hudson

& Wilkerson, 1987; Weston, 1992). For example, Weston (1992) studied and described

the kinematics of women performing the countermovement jump (CMJ) with no arm

swing and reported mean knee angles at the lowest part of the preparatory phase of the

jump were 80.5° for volleyball players and 93.3° for basketball players. Hudson and

Wilkerson (1987) studied 16 women in an effort to examine the relationship between

strength and jumping performance; they reported mean knee angles of 89.9º and 90.3º for

countermovement jumps with and without arm swing, respectively. On the high end of

values reported in the literature, Hsieh and Cheng (2016) reported knee angles of 101.1

and 109.4 for unskilled and skilled women jumpers, respectively. Based on current

evidence it would appear that many skilled jumpers use a moderate range of motion when

performing maximal vertical jumps, though there are some discrepancies in the literature.

In an effort to better understand the range of motion needed to skillfully

perform a maximal vertical jump Domire and Challis (2007) studied the influence of

squat depth during the jump on maximal vertical jump performance using both an

experimental and a computer simulation approach. In the experimental part of the study

participants performed six maximum vertical jumps without a countermovement; that is,

the jumper began all of the jumps from a static squatting position (i.e., static jump). Three

of the static jumps were performed from a preferred squat position (i.e., the participant

chose a comfortable squatting position to begin the jump from) and three of the static

jumps were from a self-selected squat position that was deeper than their originally

15

chosen preferred squat depth. Participants showed average knee flexion angles of 74.7°

and 93.8° for the preferred and self-selected deep squat positions, respectively. Although

knee angle was found to be significantly different between the two jump types, no

significant difference was found in jump height between the preferred and the self-

selected deeper squat positions. These experimental results were contradicted by the

results of the computer simulation. The computer simulated model was able to jump

higher from a deeper squat position, which mirrored the self-selected deeper squat

position used by the participants, than it was able to jump using the preferred squat

position used by the participants. It should be noted that in addition to implementing a

deeper squat, the coordination of the model also had to be modified in order to elicit the

greater jump height (Domire & Challis, 2007). These simulation findings appear to agree

with the findings of Hsieh and Cheng (2016) who reported that skilled jumpers used a

larger range of motion in the countermovement of the jump and jumped higher than their

counterparts who employed a smaller range of motion. The results from both of these

studies suggest that participants trained to jump from a deep squat position may be able

to jump higher than from a preferred position, once the appropriate coordination pattern

is established.

In contrast to the experimental and simulation results of Domire and Challis

(2007) and Hsieh and Cheng (2016), Mache (2005) found that individuals who were

asked to use a smaller range of motion were actually able to incorporate a smaller range

of motion and this modification in movement resulted in a significant increase in jump

height. In addition, when participants in the same study were examined on an individual

basis, jumpers who increased their knee flexion (i.e., participants reaching a deeper squat

16

position in the countermovement of the jump) actually exhibited a decrease in vertical

jump height (Mache, 2005). There are a couple of reasons why the results of these three

studies may have differed. One idea is related to the nature of the jumping tasks that were

studied in the respective studies; Mache (2005) examined a countermovement jump with

an arm swing whereas Domire and Challis (2007) evaluated a less “natural” static jump

with no countermovement and Hsieh and Cheng (2016) evaluated a countermovement

jump with arms akimbo. Domire and Challis (2007) also hypothesized that a larger range

of motion in the squat would provide the jumper with more time to generate muscle force

and thus result in a greater jump height. In contrast, it is possible that during a

countermovement jump, the same type of jump as those performed by the participants in

the study of Mache (2005), a more modest range of motion may assist the jumper in

maximizing the use of available stored elastic energy from the countermovement of the

jump as more time may actually provide more time for the stored elastic energy to

dissipate.

The results of Hudson and Owen (1982) tend to support the findings of Mache

(2005). Hudson and Owen (1982) studied the ability of individuals to use stored elastic

energy. In their study, 18 men and women were tested executing two different maximal

vertical jumps styles (i.e., countermovement and static jumps). For comparative purposes

the researchers looked at the five highest users of stored elastic energy (i.e., the skilled

jumpers) and the five lowest users of stored elastic energy (i.e., the less skilled jumpers).

They found that the skilled and less skilled jumpers employed 88% and 13% of their

stored elastic energy, respectively. In addition, skilled jumpers had an average knee

flexion angle of 84° compared to the less skilled jumpers, who had an average knee

17

flexion angle of 102°. As speculated by the authors, it is possible that the use of smaller

range of motion not only allowed for a more effective coordination pattern, but also a

more effective use of stored elastic energy.

Depth of Descent. Depth of descent is typically defined as the vertical

distance the body’s COM travels from an upright standing position to the lowest vertical

position of the COM in the countermovement of the vertical jump; it represents the

amount by which the body’s COM is lowered in the countermovement of the jump.

Depth of descent is less dependent on the motion of a single joint (e.g., a measure such as

knee flexion) and more reflective of the motion of the entire body.

Depth of descent has been described for a variety of jumpers (e.g., men and

women, skilled and less skilled) and varying results have been found. Hudson and Owen

(1985) studied men and women track and field athletes performing countermovement

jumps; they reported mean depths of descent of 32.4 cm and 29.3 cm for men and

women, respectively. Mache (2005) reported depths of descent ranging from 18.7 cm to

20 cm in collegiate women basketball players performing countermovement jumps.

Hudson and Wilkerson (1987) studied the variant and invariant aspects of vertical

jumping. They compared depth of descent in four different types of jumps, including

static jumps with and without an arm swing, and countermovement jumps with and

without arm swing. They found that the jumps with an arm swing had significantly

greater depth of descent than the corresponding jumps with no arm swing, for example

the average depth of descent for the countermovement jumps with arm swing was 31.0

cm compared to 28.7 cm for the countermovement jumps without arm swing. Based on

18

the present evidence it appears that the type of jump being performed influences the

depth of descent used by the jumper.

Harman, Rosentein, Frykman, and Rosentein (1990) also examined depth of

descent in the same four jump types studied by Hudson and Wilkerson (1987). For the

countermovement jumps they reported significantly different mean depths of descent

between the jumps performed with an arm swing and those performed without an arm

swing. Depths of descent were 32 cm and 35 cm for the arm swing and no arm swing

jumps, respectively. Though these findings are in disagreement with the results of

Hudson and Wilkerson (1987), wherein participants performing a countermovement jump

with arm swing had a greater range of motion than in those jumps without arm swing,

these findings still support the notion that the range of motion used will depend upon the

jump being performed.

In addition to simply describing depth of descent some researchers have

attempted to relate depth of descent to skill in jumping. Hudson and Owen (1982) found

depth of descent to be significantly correlated with the skillfulness of the jumper when

skill is defined in terms of the use of stored elastic energy. Hudson and Owen (1982)

reported that skilled jumpers (i.e., high users of stored elastic energy) had a mean depth

of descent of 25 cm compared to their less skilled counterparts (i.e., low users of stored

elastic energy), who showed an average depth of descent of 34 cm. In contrast, Hsieh and

Cheng (2016) examined countermovement jumps performed with arms akimbo and

reported depths of descent of 37 cm and 30 cm for skilled and non-skilled jumpers,

respectively. The relationship between skill and depth of descent is not clear based on

19

these two pieces of evidence, however, other less direct pieces of evidence may shed light

on this topic.

Mache (2005) was able to indirectly relate jumping performance to depth of

descent. After receiving feedback aimed at reducing the range of motion used in the

vertical jump and increasing vertical jump height, participants in the treatment group

decreased depth of descent from 18.7 cm to 16.7 cm from pre to post-feedback and were

actually able to jump a mean of 2.4 cm higher. Conversely, participants in the control

group (i.e., participants who were not asked to modify their range of motion) exhibited an

increase in depth of Descent from 20 cm to 22.2 cm from pre to post-feedback jumps and

actually experienced a decrease in mean jump height of 0.5 cm in the post-feedback

jumps. When taking a closer look at the performance of each participant as reported by

Mache (2005) only one participant out of 14 appeared to have benefited from a depth of

descent shallower than 15.5 cm. If we combine the results of Hudson and Owen (1982)

and Mache (2005) it seems appropriate to conclude that having a depth of descent

ranging between 15 and 25 cm may help to elicit a better jumping performance.

Training Methods for Improving Vertical

Jump Height

Strength, Strength Development, and Vertical Jump Height

For many years, one of the most popular means of attempting to improve

vertical jump performance has been strength training. It is often believed that increased

strength will result in increased jump height; therefore, in order to improve vertical jump

performance, many strength training programs have been implemented with this purpose

20

in mind. Based on these beliefs some early research on vertical jump performance

focused on the role of muscular strength and the effects of various methods of strength

training (Bobbert & Van Soest, 1994; Dowling & Vamos, 1993).

Dowling and Vamos (1993) examined the biomechanical force-time and

power-time curves from maximal vertical jumps. This analysis revealed that peak power

was the single best predictor of jumping performance. As traditional strength training

methods are not aimed at improving peak power, the authors concluded increased

strength alone would not be enough to ensure improvements in vertical jump

performance. The authors argued that instead of focusing on increasing strength in

isolation, increases in strength need to occur at high velocities in order to improve power

and possibly improve vertical jump performance.

The findings of Bobbert and Van Soest (1994) appear to support the work of

Dowling and Vamos (1993). Bobbert and Van Soest (1994) were able to demonstrate

with a computer simulation study that increased strength does not necessarily correspond

with improved vertical jump performance. Their model showed a decrease in jump height

by as much as 6.5 cm when strength was increased by just 10%. However, when

increases in strength were introduced to the model, in addition to modifications to the

coordination pattern, the model was able to jump 1.2 cm higher. These results suggest

that in order to take advantage of gains in strength, the coordination pattern used by the

athlete must also be modified. The authors suggest that strength training programs aimed

at improving jump performance should include exercises that allow athletes to practice

jumping. Further, they speculated that practicing jumping as the athlete is gaining

21

strength may allow for appropriate adaptations in coordination in the vertical jump to

occur; thereby allowing the athlete to reap the benefits of their increased strength.

Plyometric Training and Vertical Jump Height

Plyometrics are one possible method of enhancing strength at high velocities

and potentially enhancing vertical jump performance as suggested by Dowling and

Vamos (1993). Miller (1982) studied the effects of an eight-week plyometric training

program on jumping performance. He hypothesized that a plyometric program would

improve the vertical jump performance of adult women. Participants were assigned to a

treatment or control group. The treatment group trained once a week for eight weeks

performing 50 drop jumps (DJ) per session. Treatment participants improved jump height

by more than 5 cm after completing the eight-week program while control participants

showed no significant change in vertical jump height.

Makaruk et al. (2014) examined the chronic effects of single and repeated

jump training on vertical jump height. Untrained men with a plyometric training

background were randomly assigned to a single jump group (SJG), repeated jump group

(RJG), or control group (CON). Both experimental groups trained three times per week

on non-consecutive days for six weeks. Maximal vertical jump height was assessed

before and after the six week training protocol. Both plyometric groups significantly

improved their countermovement jump height when compared to the control group. The

SJG significantly improved jump height by 6.1 cm and the RJG group also showed a

significant improvement in vertical jump height by 3.9 cm.

22

The results from both of the described plyometric training studies lead one to

believe that when plyometrics are implemented properly, participants are able to benefit

from these methods as is evident in the increased vertical jump heights observed post-

training. However, the benefits of such methods for improving vertical jump height take a

minimum of several weeks to occur. In addition, great care must be taken in how

plyometric training programs are implemented in order to avoid overuse injuries.

Non-traditional Jump Training Methods

Because of the potential risk of injury and the time required for traditional

means of improving vertical jump performance to be effective (e.g., plyometric training

programs) some researchers have sought to find safer and more time efficient means of

improving vertical jump performance. Ross and Hudson (1997) conducted one such pre-

experimental study that sought to improve both the process and the product of the vertical

jump through a mini-trampoline training program. Participants completed two training

sessions per week on a mini-trampoline over a five-week training period. At the end of

the five-week protocol all participants had performed at least 500 vertical jumps.

Following the training program knee angles at full crouch went from a mean of 77.5º pre-

training to a mean of 75.1º post-training. Interestingly, there appeared to be a

convergence of knee flexion angles following the training period. That is, participants

who used a greater amount of flexion pre-training exhibited a reduction in range of

motion post-training; whereas participants who used a smaller amount of flexion pre-

training displayed an increase in range of motion. These changes in range of motion were

also associated with an improvement in mean jump height of 3.3 cm from pre- to post-

23

training. Based on these findings it appears that changes in maximum knee flexion are

associated with improvement in vertical jump height.

We can draw several conclusions from the literature related to using various

training methods to improve vertical jump performance. First, it appears that increases in

strength alone do not result in improvements in vertical jump performance (Dowling &

Vamos, 1993). However, increases in strength that are accompanied by adaptations in the

coordination pattern used in the vertical jump may result in improvements in vertical

jump height (Bobbert & Van Soest, 1994). A carefully implemented plyometric training

program may also be an appropriate method of eliciting improvements in vertical jump

performance. However, the downside with any of these training methods is that the

physiological adaptations necessary for improvements in performance to occur can take

several weeks and the risk of overuse injuries is high when the training methods are not

implemented correctly.

Feedback to Enhance Skill

Providing feedback to the mover with the intent of improving vertical jump

performance may be one viable alternative to implementing long strength or plyometric

training programs. Feedback has been traditionally classified into two categories: sensory

and augmented. Sensory feedback is information naturally available to the mover that

results from performing a motor task. This form of feedback is received through the

performer’s sensory systems. Augmented feedback is external information about the

motor task that supplements the naturally available information (Prapavessis & McNair,

1999). This sort of augmented feedback has in fact, proven to be effective for modifying

24

movement in many sports. For example, Guadagnoli, Holcomb, and Davis (2002)

demonstrated that participants who received augmented feedback (video or verbal)

experienced greater improvements in skill over a two-week period than those participants

who were not provided any form of augmented feedback. Furthermore, participants in

this study who received video feedback experienced greater improvements in

performance than those who simply received verbal feedback.

As range of motion appears to be a variable associated with vertical jump skill

and performance, it may be a viable option for providing feedback. Mache (2005) chose

to attempt to modify range of motion in the vertical jump with the intent of improving

vertical jump skill and vertical jump height. In this experimental study participants

performed countermovement jumps before and after receiving biomechanical feedback.

Treatment participants received feedback based on their maximum knee flexion angle

and were asked to adjust their jump by crouching more or less depending on where they

fell in a previously determined knee flexion angle target zone. Control participants were

not given any feedback. No significant differences in knee flexion angles were observed

between the pre- and post-feedback vertical jumps in the treatment or control group;

however, treatment participants did modify range of motion by decreasing the depth of

descent used during the jump. Although the difference scores for knee flexion between

groups were not statistically significant from the pre- to post-feedback jumps, participants

in the treatment group were able to jump significantly higher post-feedback.

Similar results were found by Herman et al. (2009). They studied the effects

of video assisted feedback on completing a stop-jump task. One group of participants

completed a nine-week strength training program in addition to receiving feedback,

25

whereas the second group received only feedback with no strength training period. The

video assisted feedback was sufficient to significantly alter the participants’ knee and hip

motion patterns during the stop-jump task. That is, participants who received feedback

without completing the nine-week strength training program still exhibited significant

changes in their movement patterns when performing stop-jump tasks. Although this

study was not designed to improve vertical jump performance, as is the focus of the

present study, the results illustrate the importance of feedback in improving movement

technique. In fact, the authors concluded that strength training without the inclusion of

proper instruction or technique may leave athletes without the tools necessary to

incorporate changes and appropriately alter movement patterns (Herman et al., 2009).

Other researchers have successfully used verbal feedback to modify

kinematics and kinetics during relatively simple landing tasks (Cowling, Steele, &

McNair, 2003; Etnoyer, Cortes, Ringleb, Van Lunen, & Onate, 2013; McNair,

Prapavessis, & Callender, 2000; Onate, Guskiewicz, & Sullivan, 2001; Onate et al., 2005;

Prapavessis & McNair, 1999). After receiving the simple verbal cue “…when you land I

want you to land with your knee bending” the participants of Cowling et al. (2003) were

able to exhibit greater knee flexion than they used prior to receiving verbal feedback. A

similar study also using verbal and visual feedback was able to demonstrate that a

combination of self-feedback and expert-video feedback with verbal instruction

effectively improved lower extremity kinematics during jump-landing tasks (Etnoyer et

al., 2013). Comparable results were found by Parsons and Alexander (2012) where

augmented feedback appeared to produce positive changes in landing biomechanics (i.e.,

ankle, knee, hip, and trunk flexion) in adolescent female volleyball players performing a

26

spike jump. These changes in kinematics were evident after just one session of verbal and

video feedback (Parsons & Alexander, 2012). The effects of visual and verbal feedback

on the execution of landing tasks are often immediate as previously described (Cowling

et al., 2003; Etnoyer et al., 2013; Parsons & Alexander, 2012). Long-term changes

associated with visual and verbal feedback have also been observed, providing evidence

that the positive effects of feedback on skill can have lasting effects (Etnoyer et al., 2013;

Onate et al., 2001; Onate et al., 2005; Parsons & Alexander, 2012).

Though feedback has generally proven to be effective in modifying

movement, the specificity and mode of the feedback provided appear to be very

important (Keller et al., 2014; Onate et al., 2005) . For example, Onate et al. (2005)

divided participants into four groups: expert-only feedback group (i.e., feedback was

provided by viewing an expert model trained in proper landing technique), self-only

feedback group (i.e., participants viewed their own videotaped jump-landing trial),

combination feedback group (i.e., participants viewed an expert and their own

performance), and a control group with no feedback. The authors found that the expert-

only feedback group did not differ significantly from the control group in terms of

changes in knee flexion range. However, the self-only and combination feedback groups

experienced significant increases in knee flexion angles when compared to the control

group. This suggests that videotaped augmented feedback should be specific to the

individual and include a review of the athlete’s own performance. Keller et al. (2014)

were able to demonstrate the importance of augmented feedback in drop jump

performance, in addition to observing immediate benefits of augmented feedback the

author also reported long-term benefits (i.e., over the course of 4 weeks). In this study,

27

participants were shown video of an experienced jumper performing a drop jump at the

beginning of the experiment; they were then instructed to jump as high as possible with

maximum effort. Participants received no advice with respect to knee, ankle or hip

angles. The augmented feedback in this study was provided after every jump, in the form

of providing participants with their jump height after each jump on a 22-inch monitor.

Jumps were also performed without feedback. At the beginning of the four-week

experiment participants exhibited greater vertical jump heights in the augmented

feedback condition when compared to the without feedback condition, this was also true

four weeks later.

The fact that several studies have found that feedback aids athletes in

achieving better technique leads one to believe that this method could also be applied to a

more complex skill, such as jumping, with the goal of improving vertical jump skill and

increasing vertical jump height. One attempt at using verbal feedback to improve vertical

jump performance was made by Gelpi (1997). Gelpi (1997) asked participants to reduce

knee flexion in the crouch of the jump in a way that was comfortable and profitable to

them. All participants were able to successfully reduce their knee flexion in the post-

feedback jumps but only some were able to jump higher, and this difference in jump

height was not statistically significant. Perhaps the fact that the researcher did not take

into account the pre-existing values of knee flexion, did not provide feedback specific to

the mover, and did not provide video precluded the author from finding significant

changes in vertical jump height. This study appears to further illustrate the need for

appropriate feedback that is specific to the individual.

28

A study with more specific feedback was performed a few years later; Mache

(2005) sought to investigate the efficacy of augmented (i.e., visual and verbal) feedback

in improving the process and the product of the vertical jump. Though the treatment

participants (i.e., those receiving specific feedback) were not able to reduce their knee

flexion compared to their control counterparts, they were able to modify the range of

motion used in the jump as was evident in a significant decrease in depth of descent.

Mache (2005) also found that this change in range of motion was associated with a 2.4

cm increase in jump height performance among the treatment participants. Furthermore,

the control participants who did not receive specific feedback actually exhibited a 0.5 cm

decrease in jump height, again indicating the need for specific feedback. The author’s

conclusion was that “the use of verbal and visual biomechanical feedback appears to be

an effective means for improving both the process and product of the vertical jump”

(Mache, 2005, p. 80).

These results were confirmed in a more recent study aimed at improving

vertical jump performance. Staub et al. (2013) used augmented verbal feedback in an

attempt to improve power output in the vertical jump. Participants completed a

countermovement jump protocol twice: once with feedback and once without feedback.

Feedback was provided based on the power output during the jump as measured by a

force plate. When provided specific knowledge of their performance participants were

able to exhibit greater mean power output than when knowledge of their performance

was not provided (Staub et al., 2013). While this study again indicates that feedback may

be an effective means of improving vertical jump performance, the tools needed to

provide this type of feedback (e.g., a force plate) are not as readily available as video

29

technology, making it difficult for the average physical education teacher or coach to

incorporate such knowledge.

The Use of Technology for Enhancing

Movement

Currently, video technology is at the tip of our fingers, especially with the

increasing availability of tablets (e.g., the iPad) and smartphones. Tablets are commonly

replacing the laptop as the main technology for teaching. Physical education teachers and

coaches are not strangers to this new technology and the software applications (e.g.,

Coach’ Eye, Hudl Technique) associated with such technology. Further, an increasing

number of physical education teachers and coaches are looking for meaningful ways to

integrate this technology into their physical education and health classes, practices, and

competitive games (SPARK, 2012). Despite the growing use of these tablets in physical

activity settings across the United States, research regarding the effectiveness of such

methods is currently lacking. Specifically, we don’t know how useful tablets and the

associated software applications can be to the process of enhancing movement. Because

iPads, and other video technologies, are so readily available to teachers it is imperative

that we understand how to properly incorporate these devices in the process of improving

movement. This information will help coaches and physical educators maximize the

potential of these technologies. Furthermore, it will make existing biomechanical

knowledge more useful to the average individual wishing to help themselves or others

enhance movement skill.

30

Summary

Based on this review of relevant literature we know that range of motion (i.e.,

maximum flexion knee angle and the position of the COM at takeoff) plays an important

role in skillful and successful vertical jumping. This discussion of relevant literature has

also covered how biomechanical feedback can result in a change (both immediate and

long term) in biomechanical variables, like range of motion, in tasks such as landing or

jumping. However, research involving the use of augmented feedback based on our

knowledge of the biomechanics of skillful jumping is scarce. Therefore, combining the

information we have about the kinematics of skillful jumping with video and verbal

feedback may be a viable way of helping people jump higher. Furthermore, making this

knowledge accessible to the everyday coach and physical education teacher by using

current technology (e.g., the iPad) is a necessity.

31

CHAPTER III

METHODS

The purpose of this study was to investigate whether the use of biomechanical

feedback improves vertical jump performance in recreationally active college-aged

women. A randomized controlled experimental design, with pre- and post-feedback

measurements, was used to evaluate changes in jumping performance.

Participants

Califorina State University (CSU), Chico students were invited to participate

in the study. All participants met the following inclusion criteria: they were between 18

and 30 years old, they completed at least 30 minutes of moderate to vigorous intensity

exercise at a minimum frequency of twice per week, and they were free from any

condition that would permit them from safely completing maximal vertical jumps.

Participants were not required to have any previous experience in jump training or

jumping activities. Twenty women (age 22.6 ± 3.07 years; height 1.63± 0.07 m; weight

67.4± 12 kg) who volunteered to participate and met the study inclusion criteria

completed the testing during the fall of 2014. Before testing began, participants read and

signed an informed consent document approved by the Institutional Review Board of

CSU, Chico (Appendix A).

32

Testing

In order to determine the effects of biomechanical feedback on maximal

vertical jump performance, kinematic and ground reaction force data were collected

during maximal vertical jumps performed with a countermovement with no arm swing

(i.e., arms akimbo). Data were collected during jumps completed both before and after

participants received biomechanical feedback aimed at improving vertical jump

performance. Kinematic data were measured at 120 Hz using a six-camera motion

capture system (Motion Analysis Corporation, Santa Rosa, CA, USA). Digital video was

also collected at 30 frames per second using an iPad 2 (Apple, Cupertino, CA, USA). In

addition, ground reaction forces were sampled at 1200 Hz from two force plates during

the jumping tasks to identify the instant of take-off (Kistler, Amherst, NY, USA).

Testing took place in the Cheryl Maglischo Biomechanics Laboratory at

CSU, Chico. Participants were randomly assigned to the control or the treatment group,

and they were unaware of the group they had been assigned to. Participants’ age, relevant

health history, physical activity level, and previous participation or experience in jumping

activities was recorded (Appendix B). In addition, the height and weight of each

participant was measured by the researcher using a wall-mounted stadiometer and scale,

respectively. Participants were asked to wear tight-fitting, dark clothing and their own

athletic shoes for the jump testing. Each participant was tested individually in a single

testing session that took approximately 60 minutes.

Pre-feedback

The pre-feedback testing procedures were the same for both the treatment and

the control group. The pre-feedback testing involved the following: Participants

33

completed a warm-up that consisted of a five minute self-paced ride on a stationary bike

and a series of dynamic warm-up exercises (Appendix C). After completing the warm-up

32 retro-reflective markers were attached to the skin and clothing of the participant at

specific anatomical locations to track the motion of the individual during the jumping

tasks. After all of the anatomical markers were attached, a reference trial of quiet

standing was recorded. Participants then had a chance to practice the maximal vertical

jumps until they felt comfortable with the task. The total number of practice jumps was

noted by the researcher and a minimum of three practice jumps were performed by the

participant.

After completing the practice jumps participants were required to rest one

minute before being asked to complete their pre-feedback jumps. The pre-feedback jumps

consisted of five maximal vertical jumps. During the pre-feedback jumps a 3D motion

capture system (Motion Analysis Corporation, Santa Rosa, CA, USA) was used to record

the position of the anatomical markers on the participant. At the same time, an iPad2

(Apple, Cupertino, CA, USA) was used to record 2D video of the participant performing

the maximal vertical jumps. In addition, ground reaction forces were measured using two

force plates during the jumping motion (Kistler force plates, Amherst, NY, USA).

Participants began each jump with one foot on each force plate. Participants were then

asked to jump as high as possible in every vertical jump. At the completion of each

maximal vertical jump, participants were asked to rate the quality of the jump based on a

modified version of a previously developed scale (Mache, 2005) (Appendix D). The

researcher also noted the quality of the jump at the conclusion of each jump. Participants

34

were required to rest one minute between each maximal vertical jump in order to prevent

fatigue.

Feedback

Upon completion of the pre-feedback trials one representative jump was

chosen to provide visual feedback to the participant. The quality rating of each jump

provided by both the participant and the researcher was used to aid in the selection of the

representative jump. Whenever possible, a jump rated highly by both the participant and

the researcher was used for feedback purposes. In the event the ratings of the participant

and the researcher did not agree, one of the jumps rated highly by the researcher was

used. In the event that multiple jumps met the proposed criteria for a representative jump

then one of the jumps was randomly chosen for feedback purposes.

The representative jump was used by the researcher to obtain the participants’

maximum knee flexion angle during the countermovement of the jump. This process was

completed using the iPad2 and Hudl Technique motion analysis software application,

formerly known as Ubersense, hereinafter “Hudl Technique app” (Agile Sports

Technologies Inc., Lincoln, NE, USA). Based on the work of previous researchers, the

target knee flexion angle was set between 70° and 85° (Gelpi, 1997; Hudson & Owen,

1982; Knudson & Miller, 1997; Mache, 2005; Ross & Hudson, 1997). The control group

participants received general feedback following their pre-feedback jumps. The treatment

group participants were given specific feedback based on whether they fell under, within,

or over the target knee flexion zone following their pre-feedback jumps. Participants

were placed in the respective feedback group based on their maximal knee flexion angle

35

measured using the Hudl Technique app (Agile Sports Technologies Inc., Lincoln, NE,

USA).

Feedback for control group. The control group was given a general statement:

After reviewing your jump I think you are capable of jumping higher. You can

review your jump on the iPad as many times as you wish and incorporate the

changes you deem proper while performing your next set of jumps so you can jump

higher. Here is one of your jumps, you can review the jump on the iPad as many

times as you wish and incorporate any changes you believe might help you jump

higher.

The participants were then given the opportunity to review the performance of

the jump that was choosen as their representative jump on the iPad2 with the Hudl

Technique app in slow motion and at real-time speed as many times as they wished. No

further feedback was given to the control group.

Feedback for treatment group. The feedback for the treatment group was

based on their maximal knee flexion angle in the representative jump previously chosen.

Depending on whether the participant was under, within, or over the target knee flexion

zone, the verbal feedback was the following:

Under target zone , <70°: “After reviewing your jump I think you can jump higher,

right now your knee angle at the lowest part of the jump is not deep enough and you

are outside the target zone. I think that if you bend your knees a little more while

you are performing your jump, you will be able to jump higher. Here is one of your

jumps, right now your knee angle at the lowest part of the jump is not deep enough

and you are outside the target zone, you can review the jump on the iPad as many

36

times as you wish and when you jump again you should try to bend your knees a

little more”.

Between target zone, 70°- 85°: “After reviewing your jump I think you can jump

higher, right now your knee angle at the lowest part of the jump is a little deep but

still within the target zone. Regardless, I think that if you bend your knees a little

less, staying on the highest portion of the target zone, while you are performing

your jump, you will be able to jump higher. Here is one of your jumps, you can

review the jump on the iPad as many times as you wish and when you jump again

you should try to bend your knees a little less, staying on the highest portion of the

target zone”

Over target zone, >85°: “After reviewing your jump I think you can jump higher,

right now your knee angle at the lowest part of the jump is a little deep and outside

of the target zone. If you think about bending your knees a little less while you are

performing your jump, you will be able to jump higher. Here is one of your jumps,

you can review the jump on the iPad as many times as you wish and when you jump

again you should try to bend your knees a little less”

The iPad2 with the Hudl Technique app was used to show each treatment

participant their performance in the jump chosen as their representative jump. After

receiving feedback from the researcher, the treatment participants were able to view their

maximum knee flexion angle in the crouch of the jump, and the target zone for the knee

flexion angle in the Hudl Technique app. The participants were allowed to review their

37

jump performance on the iPad2 as many times as they wished. The participants had the

opportunity to view the jump in slow motion and at real-time speed.

Post-feedback

After receiving their general feedback and watching their representative jump

on the iPad2, the control group participants were asked to perform a minimum of three

practice jumps incorporating the changes they deemed proper after watching their jump

performance on the iPad2 video recording. Once treatment participants received feedback

and reviewed their video, they were asked to perform a minimum three practice jumps

incorporating what they had been told and what they had seen in the video. If any

participant felt they needed more practice jumps they were allowed to do so and this was

noted by the researcher. Rest was provided following the practice jumps as previously

described for the pre-feedback data collection procedures.

After taking the practice jumps, the control participants were reminded that

they could jump higher and the treatment participants were reminded that they could

jump higher and of the specific biomechanical feedback they received. Participants were

then asked to perform five maximal countermovement jumps with a one minute rest

period between jumps to prevent fatigue, these were the post-feedback jumps. Data were

collected during the post-feedback jumps with the 3D motion capture system (Motion

Analysis Corporation, Santa Rosa, CA, USA), iPad2 (Apple, Cupertino, CA, USA), and

force plates (Kistler force plates, Amherst, NY, USA) as previously described for the pre-

feedback jumps.

38

Data Collection Protocol

Participants’ jumping performance was recorded at 120 Hz using a six-camera

3D motion capture system (Motion Analysis Corporation, Santa Rosa, CA, USA). Thirty-

two retro-reflective markers were taped to the participants’ skin and clothing at specified

anatomical landmarks following a modified version of the Helen Hayes marker set.

Markers were attached bilaterally at the following locations: acromion process, lateral

epicondyle of the humerus, ulnar styloid process, anterior superior iliac spine, posterior

superior iliac spine, lateral pelvis, lateral thigh, lateral femoral epicondyle, medial

femoral epicondyle, lateral shank, lateral malleolus, medial malleolus, calcaneus, and the

second metatarsal head. Additional markers were placed at the top, front, and rear of

head, and on the right upper back. The medial femoral epicondyle and medial malleolus

markers were removed after the reference trial of quiet standing trial was recorded.

The jump performance of each participant was also recorded at 30 frames per

second with an iPad2 (Apple, Cupertino, CA, USA) using the previously described Hudl

Technique app (Agile Sports Technologies Inc., Lincoln, NE, USA). The iPad2 (Apple,

Cupertino, CA, USA) was positioned on the right side of the participant and aimed

perpendicular to the sagittal plane. The iPad2 (Apple, Cupertino, CA, USA) was mounted

on a tripod approximately 7.62 m away from the participant. The iPad2 (Apple,

Cupertino, CA, USA) and Hudl Technique app (Agile Sports Technologies Inc., Lincoln,

NE, USA) were used to record video of the pre- and post-feedback vertical jumps; this

video was only used for feedback purposes.

Ground reaction force data were collected at 1200 Hz with two force plates

during the jumping tasks (Kistler, Amherst, NY, USA.) Participants began each jump

39

with one foot on each force plate. Ground reacion force data were used to identify when

the participant became airborne for the subsequent calculation of jump height.

Data Analysis and Calculations

For the data analysis, the lower extremity and pelvis was modeled as a three-

dimensional system of rigid links (Skelton Builder, Motion Analysis, Santa Rosa, CA).

The trajectories of the reflective markers attached to the participant were low-pass

filtered using a fourth-order, zero-lag Butterworth filter with a cut-off frequency of 12

Hz. The cut-off frequency was determined through the use of a residual analysis of

marker trajectories. Joint center locations and the orientation of each segment during each

trial was reconstructed from the filtered marker trajectories using transformations derived

from a reference trial of quiet standing. A Cardan rotation sequence of flexion/extension,

abduction/adduction, and external/internal rotation of the distal segment was used to

compute the three-dimensional joint angles knee. Body segment masses and center of

mass locations were determined using measured anthropometrics and previously

published data (de Leva, 1996).

In order to assess the effects of feedback on vertical jump performance the

following variables were measured and analyzed using the collected 3D kinematic data.

q Range of Motion. Range of motion was operationalized in two different ways:

1. Knee Flexion Angle. The maximum knee flexion angle during the jump.

2. Depth of descent. The vertical difference between the position of the

body’s center of mass (COM) in the standing position and its lowest position during

the jump.

40

q Jump Height. Jump height was defined as the peak height of the center of

mass during the airborne phase of the vertical jump. This peak height was determined by

finding the difference between the vertical position of the COM at takeoff and the

maximal vertical position of the COM during the airborne phase of the jump. The instant

of takeoff was identified as an ipsilateral ground reaction force less than 10 N.

Statistical Analysis

Descriptive statistics (i.e., means and standard deviations) were calculated

separately for the control and treatment groups for age, height, and weight.

For each participant, means and standard deviations of each of the dependent

variables were averaged across all trials of the same jump type (i.e., pre-feedback and

post-feedback trials, respectively). Out of twenty participants, two from the treatment

group that were in the “under target zone knee flexion” category had to be excluded from

the statistical analyses as there were no comparable control participants available for

comparison. For the remaining 18 participants, a mixed-effects, repeated measures

analysis of variance (ANOVA) was used to evaluate the effects of biomechanical

feedback on vertical jump performance. For each dependent variable, a group (control vs.

treatment) by condition (pre- vs. post-feedback) analysis was employed. The alpha level

was set at 0.05. Significant interaction effects were examined using a paired t-test or

independent t-test, as appropriate. To control the familywise error rate, the alpha level

was set at 0.025 for all post-hoc analyses. All statistical analyses were conducted in SPSS

23.0 (SPSS, Chicago, IL, USA).

41

CHAPTER IV

Abstract

The purpose of this study was to investigate the use of biomechanical feedback to

improve vertical jump performance in recreationally active women. Twenty women were

randomly assigned to the treatment or control group. Participants performed five maximal

countermovement jumps with arms akimbo before feedback and five maximal

countermovement jumps after receiving feedback. Specific visual and verbal feedback

was provided to the treatment group, while control participants were allowed to view

their jump performance on video only. Treatment participants made significant changes

in maximal knee flexion angle pre- to post-feedback; however, no changes in knee

flexion were observed among control participants. Depth of descent decreased

significantly from pre- to post-feedback among treatment and control participants.

However, changes in jump height were not observed. Although present findings suggest

specific visual and verbal feedback is an effective means of modifying movement

patterns, the knee flexion feedback in the present study was not suitable for improving

vertical jump height. Thus, research should continue to explore suitable visual and verbal

feedback for modifying movement and improving vertical jump performance.

Keywords: Augmented Feedback, Countermovement, Kinematics, Performance

Improvement, Range of Motion, Vertical Jump, Women

42

Introduction

Improvement in skill is fundamental to all sports, at every level of competition.

The vertical jump is an example of a skill for which improvements in performance result

in a greater chance of success in a competitive setting (e.g., jumping to grab a rebound in

basketball or to execute an overhead hit in volleyball). Thus, coaches and athletes alike

are constantly searching for means of increasing maximal vertical jump height to gain an

advantage over their competitors.

Extensive investigations of the biomechanics of vertical jumping have indicated

that range of motion is one of the variables crucial to vertical jump performance (Domire

& Challis, 2007; Hsieh & Cheng, 2016; Ross & Hudson, 1997); For example, some

researchers have reported that skilled jumpers use a smaller range of motion in the lower

extremity than less skilled jumpers (Hudson & Owen, 1982; Ross & Hudson, 1997);

whereas other researchers have reported that skilled jumpers may use a larger range of

motion when compared to less skilled jumpers (Hsieh & Cheng, 2016). Though range of

motion appears to be important to vertical jump performance, it remains unclear how to

incorporate this knowledge to improve vertical jump performance.

Rather than using biomechanical information related to skillful vertical jump

performance, researchers, coaches, and athletes have historically chosen to use more

indirect methods, such as strength training programs and plyometric exercises, to attempt

to improve vertical jump performance. For example, Bobbert and Van Soest (1994)

sought to enhance vertical jump performance by using strength training methods;

however, their results showed that increases in strength did not lead to improvements in

vertical jump height. These findings are in agreement with the work of other researchers

43

who have shown weak associations between leg strength and vertical jump performance

(Aragon-Vargas & Gross, 1997; Tomioka, Owings, & Grabine, 2001). Furthermore,

analysis of vertical jump force-time and power-time curves has led some to conclude that

strength alone is not enough to ensure improvements in vertical jump height (Dowling &

Vamos, 1993). This likely explains why plyometric training programs have been

consistently shown to be associated with improvements in vertical jump height (Makaruk,

Czaplicki, Sacewicz, & Sadowski, 2014; Miller, 1982). With careful implementation, it

appears that training methods aimed at improving vertical jump performance can be

effective; however, the physiological adaptations necessary for these methods to be

effective are often time consuming.

Providing augmented feedback may be a more viable, immediate, and efficient

way of using existing biomechanical knowledge of skilled jumping to elicit

improvements in vertical jump performance (Onate et al., 2005). Results of previous

studies indicate that providing visual and verbal feedback is an effective means of

modifying movement, specifically in the vertical jump (Gelpi, 1997; Keller, Lauber,

Gehring, Leukel, & Taube, 2014; Mache, 2005). However, in order for this augmented

feedback to be effective, it appears that the feedback must focus on a direct and

measurable aspect of the task, rather than the outcome of the task (Staub et al., 2013).

The use of augmented feedback based on current biomechanical evidence is particularly

exciting as athletes could potentially see immediate improvements in vertical jump

performance if they are able to successfully incorporate appropriate feedback.

The previously discussed studies are the only ones known, to this author, to have

used visual and verbal feedback with the objective of improving vertical jump height.

44

Therefore, the purpose of the present study was to investigate whether the use of

biomechanical feedback would result in improved vertical jump performance among

recreationally active college-aged women. It was hypothesized that participants who

received feedback, as opposed to those who were not given feedback, would be able to

alter knee flexion in a way that corresponded with the feedback that they were provided

and that they would also show corresponding changes in their depth of descent during the

jump. In addition, it was expected that the incorporation of the specific visual and verbal

feedback provided would be associated with increases in vertical jump height.

Methods

Participants

Twenty college-aged women (age 22.6 ± 3.07 years; height 1.63± 0.07 m; weight

67.4± 12 kg) volunteered to participate in the present study. All participants were

between 18 and 30 years old, completed at least 30 minutes of moderate to vigorous

exercise at least twice per week, and were free from any condition that would permit

them from safely completing maximal vertical jumps. Participants were not required to

have any previous experience in jump training or jumping activities. A written informed

consent form approved by the University Institutional Review Board was signed by each

participant before data collection.

Testing

In order to examine the effects of feedback on vertical jump performance,

kinematic and video data were collected during jumps completed both before and after

participants received biomechanical feedback aimed at improving vertical jump

performance. Prior to testing, participants were randomly assigned to the control or

45

treatment group, and were unaware of the group they had been assigned to. Participants

wore tight-fitting, dark clothing and their own athletic shoes for the jump testing.

Pre-feedback. The pre-feedback testing procedures were the same for both the

treatment and control group. Upon arriving to the lab participants’ height and weight

were measured, this was followed by a five minute self-paced ride on a stationary bike

and a series of dynamic warm-up exercises. Following the warm-up, participants

completed a minimum of three practice maximal vertical jumps. All maximal vertical

jumps were performed with a countermovement and arms akimbo. Once the participant

was comfortable with the jumping task and following a one minute rest data were

collected as they performed five maximal vertical jumps. At the completion of each

maximal vertical jump, participants were asked to rate the quality of the jump based on a

modified version of a previously developed scale (Mache, 2005). The researcher also

noted the quality of the jump at the conclusion of each jump using the same scale.

Participants were required to rest one minute between each maximal vertical jump.

Feedback. Upon completion of the pre-feedback trials one representative jump

was chosen to provide visual feedback to the participant and obtain the participants’

maximum knee flexion angle during the countermovement of the jump. Based on the

work of previous researchers, the target knee flexion angle was set between 70° and 85°

(Gelpi, 1997; Hudson & Owen, 1982; Knudson & Miller, 1997; Mache, 2005; Ross &

Hudson, 1997). Following the pre-feedback jumps, the control group participants

received general verbal feedback and were also shown their representative jump on the

iPad2; the treatment group participants were given specific verbal and visual feedback

based on whether they fell under, within, or over the target knee flexion zone (see Table

46

1), and were also allowed to review their jump performance on the iPad2 (Apple Inc.,

Cupertino, CA, USA) which showed their maximum knee flexion angle in the crouch of

Table 1 Visual and Verbal Feedback Provided to Control and Treatment Groups

Group

Control Treatment Visual

Participants will review performance of their representative jump on the iPad2 with the Ubersense motion analysis app in slow motion and at real-time speed as many times as they wish.

Participants will review performance of their representative jump. They will be able to view their maximum knee flexion angle in the crouch of the jump, and the target zone for the knee flexion angle in the Ubersense motion analysis app.

Participants will also be allowed to review their jump performance on the iPad2 video recording as many times as they wish. The subjects will have the opportunity to view the jump in slow motion and at real-time speed.

Under target zone (<70°)

“After reviewing your jump I think you are capable of jumping higher. You can review your jump on the iPad as many times as you wish and incorporate the changes you deem proper while performing your next set of jumps so you can jump higher”

“After reviewing your jump I think you can jump higher, right now your knee angle at the lowest part of the jump is not deep enough and you are outside the target zone. I think that if you bend your knees a little more while you are performing your jump, you will be able to jump higher. Here is one of your jumps, right now your knee angle at the lowest part of the jump is not deep enough and you are outside the target zone, you can review the jump on the iPad as many times as you wish and when you jump again you should try to bend your knees a little more”

Between target zone (70° and 85°)


“After reviewing your jump I think you can jump higher, right now your knee angle at the lowest part of the jump is a little deep but still within the target zone. Regardless, I think that if you bend your knees a little less, staying on the highest portion of the target zone, while you are performing your jump, you will be able to jump higher. Here is one of your jumps, you can review the jump on the iPad as many times as you wish and when you jump again you should try to bend your knees a little less, staying on the highest portion of the target zone”

Typ

e of

fee

dbac

k

Verbal

Over target zone (>85°)


“After reviewing your jump I think you can jump higher, right now your knee angle at the lowest part of the jump is a little deep and outside of the target zone. If you think about bending your knees a little less while you are performing your jump, you will be able to jump higher. Here is one of your jumps, you can review the jump on the iPad as many times as you wish and when you jump again you should try to bend your knees a little less”

47

the jump, and the target zone for the knee flexion angle in the Hudl Technique motion

analysis app (Agile Sports Technologies Inc., Lincoln, NE, USA). Participants were

placed in the respective feedback group based on their maximal knee flexion angle

measured using the Hudl Technique app (Agile Sports Technologies Inc., Lincoln, NE,

USA). All participants had the opportunity to review their jump in slow motion and at

real-time speed as many times as they wished.

Post-feedback. After receiving their general feedback and watching their

representative jump on the iPad2 (Apple Inc., Cupertino, CA, USA), participants were

asked to perform a minimum of three practice jumps and try to incorporate any necessary

changes to their jumping technique. After taking the practice jumps and a one minute

period of rest, the control participants were reminded that they could jump higher and the

treatment participants were reminded that they could jump higher and of the specific

verbal feedback they received during the intervention. Data were then collected as the

participants performed five maximal countermovement jumps with a one minute rest

period between jumps to prevent fatigue.

Data Collection Protocol

Participants’ jumping performance during the pre- and post-feedback vertical

jumps was recorded at 120 Hz using a six camera 3D motion capture system (Motion

Analysis Corporation, Santa Rosa, CA, USA). Thirty-two retro-reflective markers were

taped to the participants’ skin and clothing at specified anatomical landmarks following a

modified version of the Helen Hayes marker set. Markers were attached bilaterally at the

following locations: acromion process, lateral epicondyle of the humerus, ulnar styloid

process, anterior superior iliac spine, posterior superior iliac spine, lateral pelvis, lateral

48

thigh, lateral femoral epicondyle, medial femoral epicondyle, lateral shank, lateral

malleolus, medial malleolus, calcaneus, and the second metatarsal head. Additional

markers were placed at the top, front, and rear of head, and on the right upper back. The

medial femoral epicondyle and medial malleolus markers were removed after a reference

trial of quiet standing was recorded. The jump performance of each participant was also

recorded at 30 frames per second with an iPad2 (Apple, Cupertino, CA, USA) using the

Hudl Technique app (Agile Sports Technologies Inc., Lincoln, NE, USA). The iPad2

(Apple, Cupertino, CA, USA) was positioned on the right side of the participant, aimed

perpendicular to the sagittal plane, and mounted on a tripod approximately 7.62 m away

from the participant. In addition, ground reaction forces during take-off were sampled at

1200 Hz from two force plates during the jumping tasks to identify the instant of take-off

(Kistler, Amherst, NY, USA).

Data Analysis and Calculations

The lower extremity and pelvis were modeled as a three-dimensional system of

rigid links (Skelton Builder, Motion Analysis, Santa Rosa, CA). The trajectories of the

reflective markers attached to the participant were low-pass filtered using a fourth-order,

zero-lag Butterworth filter with a cut-off frequency of 12 Hz. Joint center locations and

the orientation of each segment during each trial were reconstructed from the filtered

marker trajectories using transformations derived from a reference trial of quiet standing.

A Cardan rotation sequence of flexion/extension, abduction/adduction, and

external/internal rotation of the distal segment was used to compute the knee joint angles.

Body segment masses and center of mass locations were determined using measured

anthropometrics and previously published data (de Leva, 1996). Range of motion was

49

operationalized as the maximum knee flexion angle during the countermovement of the

jump. Depth of descent was computed as the vertical difference between the position of

the body’s center of mass in the standing position and its lowest position during the jump.

Jump height was defined as the vertical distance through which the body’s center of mass

traveled from take-off to the peak height of the jump. Takeoff was identified as an

ipsilateral ground reaction force less than 10 N. The effects of feedback on vertical jump

performance in the previously described kinematic variables were analyzed using the

collected 3D kinematic data.

Statistical Analysis

Descriptive statistics (i.e., means and standard deviations) were calculated for the

control and treatment groups for age, height, and weight, respectively. For each

participant, means and standard deviations were computed for each of the dependent

variables across trials of the same jump type (i.e., pre-feedback and post-feedback trials,

respectively). Data from two treatment participants in the treatment group in the “under

target zone” feedback category were excluded from the statistical analyses as there were

no control group participants in the “under target zone” available for comparison. The

remaining 18 participants were compared using a 2 x 2 mixed effects, repeated measures

analysis of variance (ANOVA). Specifically, the effects of biomechanical feedback on

vertical jump performance were examined using a group (control vs. treatment) by

condition (pre- vs. post-feedback) analysis. Statistical significance was set at 0.05 for the

initial analyses. Significant interaction effects were analyzed with a paired t-test or

independent t-test as appropriate. Statistical significance was set at p< 0.025 for all post-

50

hoc analyses. All statistical analyses were performed using SPSS 23.0 (SPSS, Chicago,

IL, USA).

Results

Individual data for each participant have been reported in the Appendix

(Appendix F). All reported kinematic data is based on the collected 3-dimensional motion

capture data. The breakdown of participants by group (i.e., control and treatment) and

feedback group (i.e., under target zone, within target zone, and over target zone) led to

omitting two participants (i.e., treatment participants in the “under target zone”) from the

statistical analyses as there were no control participants available for comparison (see

Table 2). Results for the two treatment participants not included in the statistical analyses

are presented in Tables 3, 4, and 5. Results for the other 18 participants were statistically

compared, and are described subsequently.

Table 2 Participant Numbers by Group and Feedback Condition Based on Pre-Feedback Knee Flexion Angles

Control Treatment Under Target Zone 0 2 Within Target Zone 1 4 Over Target Zone 9 4

Table 3 Knee Flexion Angles (°) for Under the Target Zone Treatment Group Participants Participant Pre Feedback Jumps Post Feedback Jumps Treatment 5 81.2 115.1 Treatment 6 71.3 72.8

51

Table 4 Depth of Descent (cm) for Under the Target Zone Treatment Group Participants Participant Pre Feedback Jumps Post Feedback Jumps Treatment 5 15.9 30.7 Treatment 6 24.7 26.6

Table 5 Jump Height (cm) for Under the Target Zone Treatment Group Participants Participant Pre Feedback Jumps Post Feedback Jumps Treatment 5 24.1 22.8 Treatment 6 19.9 19.0

A significant group by time interaction was detected for maximum knee flexion

angle (p= 0.017) (see Tables 6 and 7). Post-hoc analyses revealed a significant effect of

feedback among treatment group participants (p=0.003), specifically the pre-feedback

Table 6 Knee Flexion (°), Depth of Descent (cm), and Jump Height (cm) Means (±SD) During Pre-feedback Maximal Vertical Jumps

Control Treatment Target zone Over target

zone Group

Average Target zone

Over target zone

Group Average

Knee Flexion

95.9±0 104.1±14.8 103.2±14.2 99.5±14.2 114.8±2.3 107.1±12.5

Depth of Descent

26.3±0 33.9±7.0 33.0±7.1 32.3±5.0 35.5±3.8 33.9±4.5

Jump Height

24.5±0 24.1±4.1 24.2±3.9 23.6±3.5 25.2±12.8 24.4±8.7

knee flexion angle was 107.1° compared to the post-feedback knee flexion angle of

86.3°. Post-hoc analyses also revealed a significant effect of group in the post-feedback

condition (p=0.004); treatment participants used 14.7° less knee flexion than the controls

in the post-feedback condition. The post-hoc analyses revealed no significant effect of

52

Table 7 Knee Flexion (°), Depth of Descent (cm), and Jump Height (cm) Means (±SD) During Post-feedback Maximal Vertical Jumps

Control Treatment Target zone Over target

zone Group

Average Target zone

Over target zone

Group Average

Knee Flexion

103.2±0 100.8±11.3 101.01±10.7 83.4±5.0 89.2±9.1 86.3±7.5

Depth of Descent

28.5±0 30.6±7.0 30.4±6.6 26.0±2.6 22.5±5.8 24.3±4.6

Jump Height

24.5±0 23.7±4.1 23.8±3.8 22.0±4.6 22.9±8.6 22.4±6.4

time among the control participants (p=0.667) and no differences in knee flexion angle

between groups in the pre-feedback condition (p=0.055).

A significant main effect of feedback was found for depth of descent (p=0.003)

(see Tables 6 and 7). Specifically, depth of descent across groups decreased from 33.4 cm

pre-feedback to 27.5 cm post-feedback. There was no significant effect of group for

depth of descent (p=0.267).

Statistical analyses for jump height revealed no significant effects of feedback

(p=0.07) or group (p=0.831) (see Tables 6 and 7).

Discussion

Researchers have demonstrated that augmented feedback can be an effective tool

for modifying a variety of movement patterns (Gelpi, 1997; Guadagnoli, Holcomb, &

Davis 2002; Herman et al., 2009; Mache, 2005; Parsons & Alexander, 2012). Based on

previous evidence it appears that visual and verbal feedback specific to an individual’s

performance and based on the knowledge of the biomechanics of skillful jumping could

be an effective tool for improving vertical jump performance (Gelpi, 1997; Mache,

53

2005). Unfortunately, literature of this nature is somewhat scarce, therefore the objective

of the current study was, to utilize knowledge of the biomechanics of skillful jumping, to

provide jumpers with visual and verbal feedback based on their own performance.

Specifically, the purpose of this study was to investigate whether the use of

biomechanical feedback was associated with improved vertical jump performance in

recreationally active college-aged women. Treatment group participants (i.e., those who

received augmented feedback) in the present study exhibited a decrease in maximal knee

flexion angle from pre- to post-feedback (i.e., they used a smaller range of motion at the

knee in the post-feedback jumps). Interestingly, both the treatment and control group

participants exhibited a significant decrease in depth of descent from pre-feedback to

post-feedback. However, none of the observed changes in range of motion were

associated with improvements in vertical jump height in either group of participants.

Maximal Knee Flexion

In the present study, the maximal knee flexion angles observed were consistent

with knee flexion angles found in previous studies (Domire & Challis, 2007; Hsieh &

Cheng, 2016; Mache, 2005; Weston, 1992). Treatment and control participants exhibited

maximal knee flexion angles in the pre-feedback jumps of 107.1° and 103.2°,

respectively. Post-feedback these numbers were 86.3° for treatment participants and

101.0° for control participants. These are similar to the maximal knee flexion angles of

women basketball players reported by Weston (1992) of 93.3°, and the unskilled jumpers

of Hsieh and Cheng (2016) of 101.1°. However, it may be important to note that maximal

knee flexion angles in the present study were much smaller than those observed among

the skilled jumpers of Hsieh and Cheng (2016).

54

Treatment participants in the current study were given feedback that was specific

to their performance and aimed at modifying the range of motion used in the lower

extremity, with the intent of improving vertical jump performance. Whereas, control

participants received augmented feedback in the form of watching their performance on

video; however, this feedback was provided in the absence of any specific instruction. As

was hypothesized treatment participants exhibited a 20.8° decrease in maximal knee

flexion from pre- to post-feedback and this decrease was the result of reductions in knee

flexion for all eight treatment participants. On the other hand, control participants did not

demonstrate any statistically significant differences in maximal knee flexion between the

pre- and post-feedback jumps, though 7 of the 10 control participants did increase knee

flexion from pre- to post-feedback. Of further note is the fact that participants in the

treatment group who were in the “over target zone” feedback group, and thus asked to

make the greatest decreases in their range of motion, exhibited a 25.6° decrease in knee

flexion. Whereas, treatment participants who were in the “within target zone” feedback

group, and thus asked to make much smaller decreases in range of motion than the “over

target zone” participants, showed a 16.1° decrease in knee flexion from pre- to post-

feedback. Participants in the “within target zone” feedback group made larger changes in

range of motion than those desired; however, the observed changes in knee flexion

among the treatment participants still matched the direction of the specific feedback

provided. That is, participants who were asked to use less knee flexion during the

jumping motion, exhibited less knee flexion post-feedback compared to pre-feedback.

The present results are in agreement with the findings of previous researchers

(Guadagnoli et al., 2002; Mache, 2005) and they help to further illustrate the importance

55

of augmented feedback that is specific to the individual’s own performance. For example,

Mache (2005) sought to increase vertical jump height by providing participants with

specific visual and verbal feedback regarding their maximal knee flexion angle. Similar

to the present findings Mache (2005) reported that specific feedback was effective in

modifying range of motion at the knee. Similarly, Guadagnoli et al. (2002) demonstrated

that participants who received augmented feedback (i.e., video and verbal or verbal

alone) experienced greater improvements in skill than those participants who were not

provided any form of feedback. Furthermore, participants who received video and verbal

feedback experienced greater improvements in performance than those who simply

received verbal feedback (Guadagnoli et al., 2002). Similarly, in the present study

participants who watched video of their own performance without receiving verbal

feedback did not make significant changes in their knee flexion angle. Considering the

work of previous authors and the results of the present study, it appears that the combined

use of visual and verbal feedback that is specific to the mover’s performance is more

effective for modifying movement than the use of a single form of feedback in isolation.

Depth of Descent

Depth of descent values found in the present study were consistent with depth of

descent values in the literature (Hudson & Owen, 1982, 1985; Hudson & Wilkerson,

1987). Treatment and control participants exhibited depths of descent in the pre-feedback

jumps of 33.9 cm and 33.0 cm, respectively. Post-feedback these numbers were 24.3 cm

for treatment participants and 30.4 cm for control participants. These values are

comparable to the depth of descent values reported by Hudson and Owen (1982), who

reported depths of descent of 25 cm for skilled jumpers and 34 cm for their non-skilled

56

counterparts. Present values for depth of descent are also similar to those reported for the

women jumpers in Hudson (1985) whose average depth of descent was 29.3 cm. Further,

Hudson and Wilkerson (1987), who also studied countermovement jumps with arms

akimbo, reported an average of 28.7 cm for depth of descent among women experienced

in jumping. On the other hand, depth of descent values observed in the present study

were much smaller than those reported for the skilled women observed by Hsieh &

Cheng (2016).

Despite the fact that the feedback provided in the current study was not specific to

depth of descent it is not surprising that when asking participants to modify range of

motion at their knee, their depth of descent also changed. Specifically, treatment

participants, who were given augmented feedback that was aimed at reducing knee

flexion during the countermovement of the jump, exhibited a corresponding decrease in

depth of descent. On average treatment participants demonstrated a 9.6 cm decrease in

depth of descent from pre- to post-feedback. Furthermore, those participants in the

treatment group in the “over target zone” feedback group, who were asked to make the

greatest changes in their range of motion, made the greatest reductions in depth of

descent, by decreasing their depth of descent from 35.5 cm in the pre-feedback jumps to

22.5 cm in the post-feedback jumps. Similarly, treatment participants in the “within target

zone” feedback group, who were asked to make small reductions in range of motion,

were also able to decrease their depths of descent from 32.3 cm pre-feedback to 26.0 cm

post-feedback. Although the changes made to range of motion by the participants in the

“within target zone” feedback group were larger than those desired, the observed changes

in range of motion still matched with the direction of the specific feedback provided.

57

That is, participants who were asked to use less knee flexion during the jumping motion

exhibited a smaller depth of descent post-feedback compared to pre-feedback.

Interestingly, control participants who received no specific feedback regarding

range of motion, also showed a statistically significant decrease in depth of descent,

though this decrease of 2.7 cm was much smaller than the changes observed in the

treatment group. The decrease in depth of descent, in the absence of specific verbal

feedback could potentially be explained by the results of Keller et al. (2014). Keller et al.

(2014) were able to demonstrate the importance of augmented feedback in drop jump

performance. In their study, participants were told to jump as high as possible and

received no advice with respect to knee, ankle or hip angles. Knowledge of performance

was provided by showing participants their jump height after each jump. The researchers

found that this form of augmented feedback resulted in immediate increases in jump

height (i.e., within a single feedback session) in addition to long-term benefits (i.e.,

sustained improvements over the course of four weeks). Interestingly and as previously

discussed, control participants in the current study did not show a significant decrease in

knee flexion angles from pre- to post-feedback; this indicates that observed changes in

depth of descent were influenced by changes in motion at joints other than the knee. It is

not clear why watching their own performance without specific instruction appeared to

encourage control participants to use a smaller range of motion in the post-feedback

condition. However, Mache (2005) also reported changes in movement patterns

following the use of visual feedback in the absence of specific instruction. In fact, these

participants who watched themselves on video tended to modify their movement

kinematics in a manner that was associated with a decrease in vertical jump height

58

(Mache, 2005). Based on the present evidence it appears that visual feedback in the

absence of verbal instruction is not an effective means of enhancing skill; however,

further investigation is needed to help clarify the present observations and develop an

improved understanding of the influence of video feedback on movement performance.

As previously discussed in the knee flexion section of this discussion, the changes

in depth of descent observed in the present study are in agreement with the findings of

Mache (2005) where visual and verbal feedback were effective in modifying range of

motion. The present findings also support previous work in which participants who

received augmented feedback (i.e., video and verbal or verbal alone) experienced greater

improvements in skill than those participants who were not provided any form of

augmented feedback (Guadagnoli et al., 2002). Thus, depth of descent results in the

current study further support the idea that the use of specific visual and verbal feedback is

more effective at modifying movement than the use of a single form of feedback.

Vertical Jump Height

Participants in the treatment group of the present study made significant

reductions in their maximal knee flexion angle and depth of descent pre- to post-

feedback, thus confirming the hypothesis that participants who were given specific visual

and verbal feedback would be able to alter range of motion in a way that matched with

the feedback provided. However, in contrast to the original hypothesis these observed

changes in range of motion were not associated with increases in vertical jump height.

Though the current findings with regard to jump height did not match the original

hypothesis that was based on existing biomechanical evidence, there are some sources of

information that help to explain the present results. In the current study, participants were

59

able to incorporate the feedback given to change range of motion in the desired manner

but this change was not associated with an increase in vertical jump height. The lack of

increase in vertical jump height is similar to the observations of Gelpi (1997), where

participants were able to make significant changes to their range of motion after

incorporating feedback but were not able to jump higher. Gelpi (1997) hypothesized that

participants were unable to increase jump height because the feedback provided was not

specific to the performance of the individual and because participants were not provided

visual feedback associated with their jumping performance. The methods employed in the

current study addressed both of these issues and yet the results did not reflect an

improvement in vertical jump height.

The lack of increase in vertical jump height in the presence of the desired changes

in range of motion could potentially be explained by a number of factors. First, it is likely

that in order to elicit improvements in jump height a new coordination pattern may need

to be adopted when making changes to range of motion. Domire and Challis (2007) were

able to demonstrate the influence of coordination using experimental and computer

simulation methods. When asked to use a larger range of motion participants in the

experimental study were not able to jump higher; but the computer simulation model

mirroring the larger range of motion used by the participants was able to jump

significantly higher after the coordination of the model was modified. In contrast, Mache

(2005) was able to observe immediate improvements in vertical jump height associated

with modification in range of motion in a group of skilled jumpers. Measures of

coordination were not reported, thus it is not known if these skilled jumpers modified

range of motion and coordination (Mache, 2005). The results of Domire and Challis

60

(2007), support the idea that when changing range of motion a new coordination pattern

needs to be adopted by the mover in order to elicit improvements in vertical jump height.

It is possible, based on the findings of Mache (2005) that skilled jumpers are able to

adopt an appropriate coordination pattern faster (i.e. within a single practice session) than

their less-skilled counterparts. In light of the present findings and previous work it seems

that adequate practice time (e.g. minutes, days, weeks, etc.) needs to be provided to the

jumpers so they have time to incorporate the necessary changes to range of motion, and

subsequently establish a new coordination pattern that is appropriate for the range of

motion being used. It also appears that the required practice time is related to the skill and

experience of the individual.

Another potential explanation for the lack of improvement in vertical jump height

in the present study is that perhaps a larger range of motion is appropriate in the vertical

jump. At present, the literature related to range of motion in the vertical jump is

somewhat contradictory. Domire and Challis (2007) hypothesized that a larger range of

motion in the squat would provide the jumper with more time to generate muscle force

and thus result in a greater jump height; however, when they asked their participants to

use a greater range of motion they did not observe increases in vertical jump height. This

would indicate that a smaller range of motion in the vertical jump is more beneficial than

a larger range of motion. However, their computer model was able to jump higher with

increased range of motion and modifications to coordination (Domire & Challis, 2007).

This partially agrees with the work of Hsieh and Cheng (2016) who observed that skilled

women jumpers used a larger range of motion in the countermovement of the jump and

were able to jump higher than less skilled jumpers. The results from both of these studies

61

suggest that participants should use a greater range of motion, and by using a greater

range of motion, they may be able to jump higher, once the appropriate coordination

pattern is established. Thus, some participants in the present study (i.e. “over target zone”

feedback group participants) may have actually benefited from their already large range

of motion and needed little to no change to their range of motion in order to maximize

their vertical jump height. Other participants in the present study may have benefited

from using a larger range of motion than their preferred range of motion. Thus, it remains

to be seen what range of motion would be most appropriate for less skilled jumpers to

maximize their vertical jump height.

The present work was largely built around the work of Mache (2005). Based on

the results of this work it was believed that a feedback intervention similar to the one

employed by Mache (2005) would be successful among a group of recreationally active

women. Several potential explanations for the differences observed between the results of

the present study and the work of Mache (2005) have already been presented in this

discussion. One last potential explanation is the slight differences in the feedback

provided to the participants between the two studies. In addition to providing specific

visual and verbal feedback to the treatment participants regarding their knee flexion angle

Mache (2005) also asked her participants to be quicker or slower depending on the

feedback category they fell under with respect to their pre-feedback knee flexion angle.

Whereas in the current study visual and verbal feedback was described, only in terms of

the jumper’s knee flexion angle. That being said, it is possible that the speed of motion

feedback provided to the participants by Mache (2005) benefited the mover in ways that

contributed to the increases in jump height observed in that study. This warrants further

62

investigation into the effects of speed of motion feedback related on vertical jump

performance.

Treatment Group “Under Target Zone”

The breakdown of participants by group (i.e., treatment and control) and feedback

(e.g., “under target zone”) led to the omission of two treatment participants in the “under

target zone” feedback group from the statistical analyses as there were no control

participants available for comparison. Though, statistical analyses were not completed,

the results of these two participants are still worthy of discussion. When examining these

two participants more closely, the results are comparable to those of participants in the

rest of the treatment group. That is, on average the treatment participants were able to

incorporate the provided feedback and modify their movement patterns in a manner that

matched with the feedback they were given. Specifically, both of the “under the target

zone” feedback group participants were asked to increase their maximal knee flexion

angle and they were able to increase their range of motion in the post-feedback jumps.

Participants 5 and 6 in the treatment “under target zone” feedback group exhibited

maximal knee flexion angles in the pre-feedback jumps of 81.2° and 71.3°, respectively.

Post-feedback these knee flexion angles were 115.1° for participant 5 and 72.8° for

participant 6. Similarly, treatment participants 5 and 6 exhibited depth of descent values

in the pre-feedback jumps of 15.9 cm and 24.7 cm, respectively. Post-feedback these

numbers were 30.7 cm for participant 5 and 26.6 cm for participant 6. Thus, both

participant 5 and 6 were asked to use a smaller range of motion and both were able to

exhibit a decrease in range of motion, though it appears that participant 6 made

reductions in range of motion at joints other than the knee. Furthermore, the magnitude of

63

change in range of motion varied greatly between these two participants despite the fact

that they were given the same feedback. Nonetheless, these findings again confirm the

hypothesis that participants who were given specific visual and verbal feedback would be

able to alter range of motion in a way that matched with the feedback provided.

Despite the desired changes in range of motion, and similar to the rest of the

participants in the treatment group, the observed increases in range of motion among

treatment participant 5 and 6 were not associated with an increase in vertical jump height

in the post-feedback jumps. One potential explanation for the lack of improvement in

vertical jump height in these two treatment participants could be based on the results of

Domire and Challis (2007). When Domire and Challis (2007) asked participants to use a

larger range of motion in the jump than their preferred range of motion they did not

observe improvements in vertical jump height. As previously discussed, Domire and

Challis (2007) hypothesized that in order to use a modified range of motion to elicit gains

in jump height a new coordination pattern may need to be established. Thus, comparable

to the rest of the treatment participants in the present study, these two participants could

also potentially benefit from adequate practice time (e.g. days, weeks, etc.) in order to

establish the new coordination patterns needed to jump higher.

The present study is not without limitations. First, the sample size was small

(n=20) and thus when stratifying participants to feedback groups some groups were left

with a limited number of participants. That being said, the present sample still allowed

for meaningful comparisons between the treatment and control groups and provided

valuable insight related to the use of visual and verbal feedback. Next, given the skill

level of the participants in the present study the time that they had to practice and

64

incorporate verbal and visual feedback may have been too short to elicit improvements in

vertical jump height. However, the time provided was consistent with previous work and

it is now evident that with less skillful individuals the duration of feedback and practice

may be important factors in eliciting improvements in performance. Despite the discussed

limitations, the present work yields valuable information related to the use of

biomechanical feedback in modifying movement and improving performance.

Conclusions

Recreationally active college-aged women in the present study were able to

successfully incorporate specific visual and verbal feedback based on their own

performance to modify the range of motion used in the vertical jump. However, these

changes in range of motion occurred in absence of the hypothesized improvements in

vertical jump performance. Nevertheless, the present findings support the idea that in

order to be effective in modifying movement, feedback should be specific to the mover’s

performance and should be provided using both visual and verbal means. Furthermore,

current results indicate that the skill level of the individual may influence the time needed

to incorporate changes in movement kinematics to elicit improvements in range of

motion. Future investigators should consider how much time is adequate for non-skilled

jumpers to incorporate changes to their range of motion and adopt new coordination

patterns. Researchers should also continue to work to identify the appropriate range of

motion (i.e. larger or smaller) to use to maximize vertical jump height.

65

References

Aragon-Vargas, L. F., & Gross, M. M. (1997). Kinesiological factors in vertical jump

performance: Differences among individuals. Journal of Applied Biomechanics,

13, 24-44.

Bobbert, M. F., & Van Soest, A. J. (1994). Effects of muscle strengthening on vertical

jump height: A simulation study. Medicine and Science in Sports and Exercise,

26(8), 1012-1020.

de Leva, P. (1996). Adjustments to Zatsiorsky-Seluyanov’s segment inertia parameters.

Journal of Biomechanics, 29(9), 1223-1230.

Domire, Z. J., & Challis, J. H. (2007). The influence of squat depth on maximal vertical

jump performance. Journal of Sports Sciences, 25(2), 193-200.

Dowling, J. J., & Vamos, L. (1993). Identification of kinetic and temporal factors related

to vertical jump performance. Journal of Applied Biomechanics, 9, 95-110.

Gelpi, J. (1997). Efficacy of a biomechanical intervention for improving the vertical jump

(Unpublished master’s thesis). California State University, Chico.

Guadagnoli, M., Holcomb, W., & Davis, M. (2002). The efficacy of video feedback for

learning the golf swing. Journal of Sports Sciences, 20, 615-622.

Herman, D. C., Oñate, J. A., Weinhold, P. S., Guskiewicz, K. M., Garrett, W. E., Yu, B.,

& Padua, D. A. (2009). The effects of feedback with and without strength training

on lower extremity biomechanics. The American Journal of Sports Medicine,

37(7), 1301-1308. doi: 10.1177/0363546509332253

66

Hsieh, C., & Cheng, L. (2016). Kinematic factors in countermovement jump for female

volleyball players with different skill levels. International Journal of Sports

Science, 6(1), 6-10.

Hudson, J. L., & Owen, M. G. (1982). Kinematic correlates of utilization of stored elastic

energy. Medicine and Science in Sports and Exercise, 14, 152.

Hudson, J. L., & Owen, M. G. (1985). Performance of females with respect to males: the

use of stored elastic energy. In D. A. Winter, R. W. Norman, R. P. Wells, K. C.

Hayes, and A. E. Patla (Eds.), Biomechanics IX-A (pp. 50-54). Champaign, IL:

Human Kinetics.

Hudson, J. L., & Wilkerson, J. D. (1987, July). Variance and invariance in vertical

jumping. Paper presented at the XI International Congress of Biomechanics,

Amsterdam, The Netherlands.

Keller, M., Lauber, B., Gehring, D., Leukel, C., & Taube, W. (2014). Jump performance

and augmented feedback: Immediate benefits and long-term training effects.

Human Movement Science, 36, 177-189.

Knudson, D. & Miller, G. (1997) Kinesiology/physical education: Half-full or half-

empty. Journal of Physical Education, Recreation & Dance, 68(4), 6-8.

Mache, M. (2005). The use of biomechanical feedback to improve vertical jump

performance (Unpublished master’s thesis). California State University, Chico.

Makaruk, H., Czaplicki, A., Sacewicz, T., & Sadowski, J. (2014). The effects of a single

versus repeated plyometrics on landing biomechanics and jumping performance

in men. Biology of Sport, 31(1), 9-14. doi: 10.5604/20831862.1083273

67

Miller, B. P. (1982). The effects of plyometric training on the vertical jump performance

of adult female subjects. British Journal of Sports Medicine, 16, 113. doi:

10.1136/bjsm.16.2.113

Onate, J. A., Guskiewicz, K. M., Marshall, S. W., Giuliani, C., Yu, B., & Garrett, W. E.

(2005). Instruction of jump-landing technique using videotape feedback: Altering

lower extremity motion patterns. The American Journal of Sports Medicine,

33(6), 831-842. doi: 10.1177/0363546504271499.

Parsons, J. L., & Alexander, M. J. L. (2012). Modifying spike jump landing

biomechanics in female adolescent volleyball athletes using video and verbal

feedback. Journal of Strength and Conditioning Research, 26(4), 1076-1084.

Ross, A. L., & Hudson, J. L. (1997). Efficacy of a mini-trampoline program for

improving the vertical jump. In J. D. Wilkerson, K. M. Ludwig, & W. J.

Zimmermann (Eds.), Biomechanics in Sports XV (pp. 63-69). Denton, TX: Texas

Woman's University.

Staub, J. N., Kraemer, W. J., Pandit, A. L., Haug, W. B., Comstock, B. A., Dunn-Lewis,

C.,…& Hakkinen, K. (2013). Positive effects of augmented verbal feedback on

power production in NCAA division I collegiate athletes. Journal of Strength and

Conditioning Research, 27(8), 2067-2072.

Tomioka, M., Owings, T. M. & Grabiner, M. D. (2001). Lower extremity strength and

coordination are independent contributors to maximum vertical jump height.

Journal of Applied Biomechanics, 17, 181-187.

68

Weston, J. (1992). A study of biomechanical comparison in the countermovement jump

and the drop jump, performed by female intercollegiate athletes. (Unpublished

doctoral dissertation). Texas Woman’s University.

REFERENCES

70

REFERENCES

Aragon-Vargas, L. F., & Gross, M. M. (1997a). Kinesiological factors in vertical jump

performance: Differences among individuals. Journal of Applied

Biomechanics, 13, 24-44.

Aragon-Vargas, L. F., & Gross, M. M. (1997b). Kinesiological factors in vertical jump

performance: Differences within individuals. Journal of Applied

Biomechanics, 13, 45-65.

Bobbert, M. F., & Van Ingen Schenau, G. J. (1988). Coordination in vertical jumping.


Bobbert, M. F., & Van Soest, A. J. (1994). Effects of muscle strengthening on vertical

jump height: A simulation study. Medicine and Science in Sports and

Exercise, 26(8), 1012-1020.

“Center of Mass.” (n.d.). In Merriam-Webster online dictionary (11th ed.). Retrieved from

https://www.merriam-webster.com/dictionary/centerofmass

Cowling, E. J., Steele, J. R., & McNair, P. J. (2003). Effect of verbal instructions on

muscle activity and risk of injury to the anterior cruciate ligament during

landing. British Journal of Sports Medicine, 37, 126-130.

de Leva, P. (1996). Adjustments to Zatsiorsky-Seluyanov’s segment inertia parameters.


71

Domire, Z. J., & Challis, J. H. (2007). The influence of squat depth on maximal vertical

jump performance. Journal of Sports Sciences, 25(2), 193-200.

Dowling, J. J., & Vamos, L. (1993). Identification of kinetic and temporal factors related

to vertical jump performance. Journal of Applied Biomechanics, 9, 95-110.

Etnoyer, J., Cortes, N., Ringleb, S. I., Van Lunen, B., L., & Onate, J. A. (2013).

Instruction and jump-landing kinematics in college-aged female athletes over

time. Journal of Athletic Training, 48(2), 161-171.

Guadagnoli, M., Holcomb, W., & Davis, M. (2002). The efficacy of video feedback for

learning the golf swing. Journal of Sports Sciences, 20, 615-622.

Gelpi, J. (1997). Efficacy of a biomechanical intervention for improving the vertical jump

(Unpublished master’s thesis). California State University, Chico.

Harman, E. A., Rosentein, M. T., Frykman, P. N., & Rosentein R. M. (1990). The effects

of arms and countermovement on vertical jumping. Medicine and Science in

Sports and Exercise, 22(6), 825-833.

Herman, D. C., Oñate, J. A., Weinhold, P. S., Guskiewicz, K. M., Garrett, W. E., Yu, B.,

& Padua, D. A. (2009). The effects of feedback with and without strength

training on lower extremity biomechanics. The American Journal of Sports

Medicine, 37(7), 1301-1308. doi: 10.1177/0363546509332253

Hsieh, C., & Cheng, L. (2016). Kinematic factors in countermovement jump for female

volleyball players with different skill levels. International Journal of Sports

Science, 6(1), 6-10.

72

Hudson, J. L. (1986). Coordination of segments in the vertical jump. Medicine and

Science and Sports and Exercise,18(2), 242-251.

Hudson, J. L. (1990). Drop, stop, pop: Keys to vertical jumping. Strategies (June), 11-14.

Hudson, J. L. (1995). Core concepts of kinesiology. Journal of Physical Education,

Recreation and Dance (May-June), 54-55, 59-60.

Hudson, J. L., & Owen, M. G. (1982). Kinematic correlates of utilization of stored elastic

energy. Medicine and Science in Sports and Exercise, 14, 152.

Hudson, J. L., & Owen, M. G. (1985). Performance of females with respect to males: the

use of stored elastic energy. In D. A. Winter, R. W. Norman, R. P. Wells, K.

C. Hayes, and A. E. Patla (Eds.), Biomechanics IX-A (pp. 50-54). Champaign,

IL: Human Kinetics.

Hudson, J. L., & Wilkerson, J. D. (1987, July). Variance and invariance in vertical

jumping. Paper presented at the XI International Congress of Biomechanics,

Amsterdam, The Netherlands.

Keller, M., Lauber, B., Gehring, D., Leukel, C., & Taube, W. (2014). Jump performance

and augmented feedback: Immediate benefits and long-term training effects.

Human Movement Science, 36, 177-189.

“Kinematics.” (n.d.). In Merriam-Webster online dictionary (11th ed.). Retrieved from

https://www.merriam-webster.com/dictionary/kinematics

Knudson, D. & Miller, G. (1997) Kinesiology/physical education: Half-full or half-

empty. Journal of Physical Education, Recreation & Dance, 68(4), 6-8.

73

Mache, M. (2005). The use of biomechanical feedback to improve vertical jump

performance (Unpublished master’s thesis). California State University,

Chico.

McNair, P. J., Prapavessis, H., & Callender, K. (2000). Decreasing landing forces: Effect

of instruction. British Journal of Sports Medicine, 34, 293-296.

Makaruk, H., Czaplicki, A., Sacewicz, T., & Sadowski, J. (2014). The effects of a single

versus repeated plyometrics on landing biomechanics and jumping

performance in men. Biology of Sport, 31(1), 9-14. doi:

10.5604/20831862.1083273

Miller, B. P. (1982). The effects of plyometric training on the vertical jump performance

of adult female subjects. British Journal of Sports Medicine, 16, 113. doi:

10.1136/bjsm.16.2.113

Onate, J. A., Guskiewicz, K. M., Marshall, S. W., Giuliani, C., Yu, B., & Garrett, W. E.

(2005). Instruction of jump-landing technique using videotape feedback:

Altering lower extremity motion patterns. The American Journal of Sports

Medicine, 33(6), 831-842. doi: 10.1177/0363546504271499

Onate, J. A., Guskiewicz, K. M., & Sullivan, R. J. (2001). Augmented feedback reduces

jump landing forces. Journal of Orthopaedic and Sports Therapy, 31(9), 511-

517.

Parsons, J. L., & Alexander, M. J. L. (2012). Modifying spike jump landing

biomechanics in female adolescent volleyball athletes using video and verbal

feedback. Journal of Strength and Conditioning Research, 26(4), 1076-1084.

74

SPARK. (2012, April 20). Physical education (PE) apps for teachers [Web log comment]

Retrieved from http://www.sparkpe.org/blog/physical-education-pe-apps-for-

teachers/

Prapavessis, H., & McNair, P. J. (1999). Effects of instruction in jumping technique and

experience jumping on ground reaction forces. Journal of Orthopaedic and

Sports Physical Therapy, 29(6), 352-356.

Ross, A. L., & Hudson, J. L. (1997). Efficacy of a mini-trampoline program for

improving the vertical jump. In J. D. Wilkerson, K. M. Ludwig, & W. J.

Zimmermann (Eds.), Biomechanics in Sports XV (pp. 63-69). Denton, TX:

Texas Woman's University.

Staub, J. N., Kraemer, W. J., Pandit, A. L., Haug, W. B., Comstock, B. A., Dunn-Lewis,

C.,…& Hakkinen, K. (2013). Positive effects of augmented verbal feedback

on power production in NCAA division I collegiate athletes. Journal of

Strength and Conditioning Research, 27(8), 2067-2072.

Tomioka, M., Owings, T. M. & Grabiner, M. D. (2001). Lower extremity strength and

coordination are independent contributors to maximum vertical jump height.

Journal of Applied Biomechanics, 17, 181-187.

Weston, J. (1992). A study of biomechanical comparison in the countermovement jump

and the drop jump, performed by female intercollegiate athletes.

(Unpublished doctoral dissertation). Texas Woman’s University.

Whiting, W. C. & Zernicke, R. F. (1998). Biomechanics of musculoskeletal injury.

Champaign, IL: Human Kinetics.

APPENDIX A

76

Informed Consent for Participation in Research

Project Title: Improving Vertical Jump Performance with Biomechanical Feedback

Investigators: Paula García Krauss1, Master’s Student, Department of Kinesiology, CSU, Chico Melissa Mache2, PhD, Department of Kinesiology, CSU, Chico

Phone Number: 1916.230.7684 Email: [email protected] 2530.898.6617 [email protected]

You are being invited to participate as a subject in a student Master’s Thesis for the Kinesiology Department at CSU Chico. The purpose of this research is to help individuals achieve greater performance in the vertical jump. The information gathered from this investigation will allow researchers to better understand means of improving vertical jump performance.

If you indicate a willingness to participate in the study, you will be asked to come to the CSU, Chico Biomechanics Lab on one occasion for an approximately one hour testing session. Researchers will measure your height and weight, and you will be asked to complete a brief questionnaire regarding your physical activity level and experience. Following a warm-up, reflective markers will be attached to your skin and your jumping performance will be recorded using a 3D Motion capture system and iPad as you perform five maximal vertical jumps. After receiving some form of instruction and practicing, you will again be asked to perform five maximal vertical jumps. In addition to the previously mentioned data, we may also collect data with a force platform (a small platform embedded in the ground that measures how hard you push on the ground) and a voice recording device.

To maintain confidentially, the video recording of the iPad will remain in the possession of the researcher until the project is completed. At that time, the recording will be destroyed by the student researcher and research committee chair. Neither the student researcher nor the committee chair will show your performance to anyone without your expressed consent. In other words, your performance will remain confidential to persons outside the research committee unless you waive this right.

The removal of the adhesive tape represents the greatest discomfort associated with this research. The risks are no greater than those associated with moderate exercise in healthy, young adults. The procedures being used are standard practice in the field of biomechanics. The benefits you can get from participating in this study are that you may learn how to perform the jump more skillfully.

In the unlikely event that you become injured as a result of your participation in this study, emergency medical care is available. You may choose to stop your participation in the study at any time during the testing session. Your decision will be respected and will not result in any penalty.

Please feel free to contact anyone of the investigators if you have any questions or concerns about this research project or your participation. Your participation is voluntary. Having read the above and having had an opportunity to ask any questions, please sign below if you would like to participate in this research. A copy of this form will be given to you to retain for future reference.

_____________________________________ Participant Name (Please Print) _____________________________________ _______________ Participant Signature Date _____________________________________ _______________ Researcher Signature Date

APPENDIX B

78

79

APPENDIX C

81

Dynamic Warm-Up Exercises

Knee to Chest (2 x 10 repetitions)

Kick back (2 x 20 meters)

High knees (2 x 20 meters)

High knees, extend leg in front (2 x 20 meters)

Lateral squat (2 x 10 repetitions)

Three side steps touch the floor (2 x 20 meters)

APPENDIX D

83

PARTICIPANT JUMP PERFORMANCE SCALE (Adapted from Mache, 2005)

5 BEST JUMP: Everything felt great, on balance, coordinated, explosive. I don’t feel like I can jump any better.

4 GREAT JUMP: The jump felt comfortable, with good balance, coordinated but

something was missing. I feel like I can do a little better.

3 AVERAGE JUMP: A typical jump, everything felt normal, small errors (maybe issues with balance or coordination).

2 BELOW AVERAGE: It didn’t feel right, off balance, uncoordinated, not explosive. 1 WORST JUMP: Off balance, uncoordinated, overall poor jump, nothing felt right.

Mache, M. (2005). The use of biomechanical feedback to improve vertical jump performance (Unpublished master’s thesis). California State University, Chico.

APPENDIX E

85

Knee flexion (°), Depth of Descent (cm), and Jump Height (cm) data for all participants and for pre-and-post-feedback jumps

Group/Subject Feedback KFBF KFAF DDBF DDAF JHBF JHAF C01 2 111.2 117.6 40.4 42.8 26.5 24.8 C02 2 94.1 81.2 34.9 24.8 26.8 29.6 C03 2 139.7 98.0 47.6 26.2 18.9 19.6 C04 2 90.1 93.2 27.7 29.5 17.2 16.1 C05 2 106.0 109.9 * * 26.9 26.4 C06 2 101.9 103.2 30.5 32.5 28.7 26.6 C07 2 98.0 111.8 31.1 35.4 20.4 21.6 C08 1 95.9 103.2 26.3 28.5 24.5 24.5 C09 2 98.3 100.4 32.4 33.0 25.1 23.7 C10 2 97.1 91.9 26.5 20.0 26.5 25.1 T01 2 115.5 91.6 36.5 24.3 14.1 15.5 T02 2 111.3 86.6 40.4 28.6 28.3 27.3 T03 1 98.0 78.9 33.4 25.6 23.7 19.6 T04 1 84.1 83.9 29.5 27.9 28.3 28.9 T05 0 81.2 115.1 15.9 30.7 24.1 22.8 T06 0 71.4 72.8 24.7 26.6 19.9 19.0 T07 1 97.2 90.3 27.4 22.5 22.0 20.1 T08 1 118.5 80.6 38.8 28.2 20.2 19.4 T09 2 116.1 100.0 31.5 22.1 16.2 15.9 T10 2 116.2 78.3 33.7 14.9 42.0 32.8

C: control; T: treatment; KF: Knee flexion; DD: Depth of descent; JH: Jump height; BF: before feedback (pre); AF: after feedback (post); Feedback 0: Under target zone; Feedback 1: Within target zone; Feedback 2: Over target zone *data unavailable for analysis

Documents

IMPROVING VERTICAL JUMP PERFORMANCE WITH