Observing and Analyzing Performance (1)• The Nature of Skills

– Movement patterns - a general series of movements having common elements. Ex: running, jumping, walking, throwing, striking, pushing

– Skill - adaptation of general movement pattern to constraints of a particular task. Ex: high jump, baseball hitting, softball pitching

– Technique - a particular type of the same skill. Ex: power hitter, contact hitter

– Style - individual adaptations of a technique. Ex: short backswing, no stride

– Constraints - limitations associated with the event. Ex: rules, equipment, environment, limitations of performer.

Observing Performance (2)• Classification of Skills According to type of

environment:– Open - unpredictable environment. Ex. baseball

hitting, jump shot– Closed - predictable environment. Ex: free throw, golf

shot, high jump

• Classification according to how it is done– Discrete - definite beginning and ending. Ex: jump

shot, shot put, high jump• Repeated discrete - assembly line, tennis forehand. (Subject to

repetitive motion disorders)

– Continuous - no definite beginning and ending. Ex: running, walking, work tasks

Oberving performance (3)• Observing Skill Performances

– Discrete skills - divide into phases such as (1) preparation, (2) execution, (3) follow-through/recovery

– Continuous/cyclic - select one cycle and divide it into phases. Ex: support, swing phases in walking

• The analysis (holistic model)– Identify overall performance objective (OPO) –(Table next slide)

• When two or more objectives are identified, priority must be set (e.g., speed vs accuracy

– Divide skill into discrete parts. Ex. Stance, stride, swing, follow-through

– Identify the mechanical purpose (MP) of each discrete part

– List the biomechanical factors and principles. Ex:: momentum conservation

– List the critical features of each part - movements that must be performed for successful execution of the skill (keys to focus on, e.g., knee extended at impact)

• Example – article on baseball hitting

Analysis Models – the Why?

• Holistic – same as Kreighbaum, Adrian p. 18-19– Read literature and use prior experience to figure out

what to focus on (ex: handout on baseball hitting)

• Factors-results – Adrian p. 17-18– Analytical, heirarchial, deterministic– Only useful for goal-oriented skills– Example – article by Hay

Analysis Methods• Qualitative vs quantitative

– Types and precision of data needed, not the tool available, dictates selection of tool

• Naked-eye observational procedures– Observational plan necessary to be consistent and

reliable• View multiple times• View from multiple perspectives• Focus on parts, then whole, then parts• Form a visual-mental image of the performance• Use a checklist – borrow or construct your own

Constructing Analysis Checklists• Procedures

– Study other checklists. Refer to specific sports/skills chapters in textbooks– Read literature to determine what factors are important– List the determinants of skilled and unskilled actions– Arrange checklist in a scale (dichotomous, continuum)

• Common factors usually included in checklists– Location of COM relative to base of support– Width of base of support– Range and path of movement of various body segments– Sequencing of segment movements– Projection angleof objects released or struck & total body COM– Overall perception of movement’s effectiveness, smoothness, etc.

Videographic and Cinematographic Analyses

• Qualitative procedures– Contourograms– Point plots– Stick figures

• Quantitative analysis -the process (APAS handout)– Videotaping– Frame grabbing – converting images to digital form– Digitizing – locating segment endpoints in space and time– Calculations done by computer

• Applying the multiplier or converting coordinates to life size• Smoothing coordinates• Calculating parameters for each segment and body COM

– Linear displacement, velocity, acceleration and inverse dynamics– Angular displacement, velocity, acceleration and inverse dynamics

• Displaying output (Digital as well as graphic)

Other Analysis Procedures

• Optoelectric imaging– Active or passive markers

• Dynamographic analysis – F orce platforms, load beams, strain gauges

• Accelerometric analysis – Vibrations, impacts, rapidly changing motions

• Electrogoniometric analysis – Joint and segment angles

• Electromyography– When and to what degree is a muscle active?– Fatigue estimate

Begin swing: 183 ms PC

Bat Vibrations During Swing & Impact

-4

-3

-2

-1

0

1

2

3

4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Time (s)

Str

ain

(v

)

Horiz DirVert DirMagnitudeHoriz DirVert DirMagnitude

Begin Swing 233ms PC

Peak 41 ms PC

Horiz Pk 38 ms PC

Bending Direction During Swing & Impact

-250

-200

-150

-100

-50

0

50

100

150

200

250

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Time (s)

Dir

ec

tio

n (

de

g)

Beg Sw - 233 ms PC

O0 is horiz & back - 21 ms PC

Approximate position when peak bending andPeak torque occurs ~ 40 ms PC