Chapter 4 Lecture © 2014 Pearson Education, Inc. Improving Muscular Strength and Endurance

Chapter 4 Lecture

© 2014 Pearson Education, Inc.

ImprovingMuscular Strength and Endurance


Learning Objectives

• Explain the benefits of developing muscular strength and endurance

• Describe how muscles contract • Distinguish between the muscle fiber types• Classify the types of muscular contractions • Identify the changes that occur in response to strength

training• List the factors that determine muscle strength and

endurance• Outline the principles used in designing a strength and

endurance program• Distinguish between the types of training programs• Design a program for improving strength and endurance


Strength Training in Daily Life

• Reduces joint and/or muscle injuries from exercise

• Reduces low back pain• Delays and reduces age-related decreases in

strength• Helps prevent osteoporosis• Increases resting energy expenditure (also

called resting metabolic rate)


Muscle Structure and Function

• There are about 600 skeletal muscles in the body

• Primary function: provide force for movement and maintain posture and regulate temperature

• Muscles shorten or lengthen, causing bones and body to move

• Muscle structure: fibers, fascia, tendons• Muscle function: motor nerves and muscle fibers

are a motor unit


Structure of Skeletal Muscle


Major Muscles of the Body


A Motor Unit


Skeletal Muscle Exercise Classifications

Isotonic (dynamic)• Movement of a body part at a joint• Most exercise and sports are isotonic

Isometric (static)• Uses muscle tension but involves no

movement• Good way to develop strength after injury

Isokinetic• Performed at a constant velocity• Uses machines that provide resistance

throughout the full range of motion


Muscle Action Classifications

Isometric Action• Actions are static and involve no movement• Occurs during isometric exercise

Concentric Action (positive work)• Muscle shortens during movement against gravity or

resistance• Example: upward arm movement during a bicep curl

Eccentric Action (negative work)• Muscle lengthens during movement against gravity or

resistance• Example: downward arm movement during a bicep

curl


Concentric and Eccentric Muscle Actions


Skeletal Muscle Fibers Types

Slow-Twitch Fibers• Contract slowly• Generate little force but are resistant to

fatigueFast-Twitch Fibers• Contract quickly• Generate lots of force, but fatigue quickly

Intermediate Fibers• Serve as a combination of the other two types• Contract rapidly, produce great force, and

resist fatigue


Fiber Type Variations

• Most people have roughly equal numbers of all three types

• Elite endurance runners/marathoners have more slow-twitch fibers

• Elite speed runners/sprinters have more fast-twitch fibers• There is a possible genetic link between a predominance

of fast-twitch fibers and certain diseases, such as obesity and diabetes

• Research indicates fibers might be able to convert from one type to another through training

• Fiber recruitment - process involving more muscle fibers to increase muscle force


Recruitment of Muscle Fiber Type


Muscular Strength

Amount of force muscle can generate, based on• Size of the muscle (primary factor)

– The larger the muscle, the greater the force produced

• Number of muscle fibers recruited during a movement

– The more fibers that are stimulated, the greater the force generated


Muscle Fiber Recruitment and Muscular Force


Evaluating Muscular Strength and Endurance

Muscular Strength Test• One-repetition maximum (1 RM) test

– Measures maximum amount of weight that can be lifted one time (recommend for experienced lifters only)– See lab 4.1 for evaluation worksheet

– Estimated 1 RM test, to reduce possible injury (recommended for beginner to intermediate lifters) – See lab 4.2 for evaluation worksheet

Muscular Endurance Tests• Push-up test• Sit-up or curl-up test

– See lab 4.4 for evaluation worksheet


Program Design Principles

Progressive Resistance Exercise (PRE)• Application of overload principle • Progressively increase amount of resistance

in the trainingSpecificity of Training• Development is specific to

– muscle group being exercised– training intensity

• High-intensity training increases muscle size and strength

• Low-intensity training increases endurance


Improving Muscular Strength and Endurance


Strength Training Adaptations

Physiological Changes• Fiber recruitment patterns change• Hypertrophy: increase in muscle size due to fiber size increase• Not common: hyperplasia, the formation of new muscle fibers

Rate of Improvement• Depends on initial strength level• Rapid strength gains in relatively untrained beginners• More gradual gains in trained people with high levels of strength

Gender Differences• Little difference in initial responses to strength training• After long-term training, men show greater gains due to higher

testosterone levels• Women DO NOT exhibit bulky muscles


Weight Training Program Design

Safety Concerns• Use spotters• Don't drop weights• Always warm up• Breathe during exercises• Use slow movements• Start with light weights and work up gradually

Types/Modes of Programs • Isotonic–most common• Isometric–least common, valsalva maneuver• Isokinetic–not practical


Exercise Prescription

Frequency• Number of training days per week• 2–3 days per week is optimal for strength gains

Intensity• Measured by the Repetition Maximum (RM)• The number of consecutive repetitions performed

without resting is a setTime (duration)• Total number of sets performed• Programs utilizing 3 sets result in greatest strength

gains


Strength Gains: Based on Sets and Repetitions


Exercise Prescription

Starter Phase• 1–3 weeks • Lighter weights, more repetitions• Do only 1 set per exercise• Frequency: twice a week

Slow Progression Phase• 4–20 weeks• Heavier weights, fewer repetitions• Increase sets per exercise to 2–3• Increase frequency to 2–3 times per week

Maintenance Phase• Starts around week 20• Requires a long-term commitment to maintain gains• The effort needed to maintain gains is not as great as the initial effort• As little as one workout a week can maintain strength


Guidelines and Precautions Prior to Beginning a Strength-Training Program


Staying Motivated

• Make time to train regularly • Make training fun • Find workout space or a facility you like• Plan a program that's challenging but enjoyable• Develop a realistic routine: don't make it so hard you'll

get discouraged• Work out with a friend or training partner• Remember the benefits of strength training: better

appearance, higher self-esteem, improved metabolism, and a feeling of accomplishment

• Complete the Steps for Behavior Change activity in the chapter if you feel reluctant to strength train


Sample Exercise Prescription for Weight Training: Beginner


Sample Exercise Prescription for Weight Training: Intermediate


Sample Exercise Prescription for Weight Training: Advanced


Summary

• Strength training can reduce back pain, decrease injuries, enhance bone health, and maintain age-related working capacity

• Strength is dependent on muscle size and fiber recruitment

• There are three major types of human skeletal muscles: slow-twitch, fast-twitch, and intermediate

• The amount of slow, fast, and intermediate muscles varies among individuals. There is a relationship between fiber type and success in some athletics. There may be a genetic connection between muscle fiber types and some diseases.

• Fiber recruitment is the process of involving more muscle fibers to produce increased force


Summary (cont.)

• Progressive resistance exercise (PRE) is the overload principle applied to resistance training

• Individualized programs can be specific for strength or endurance gains through mode, number of repetitions, and sets

• Isotonic (dynamic) exercises involve movement of a body part at a joint. Isometric (static) exercises use muscle tension but involve no movement. Isokinetic exercises are peformed at a constant velocity, often using machines.

• A strength training program has three phases: starter, slow progression, and maintenance

Documents

Chapter 4 Lecture © 2014 Pearson Education, Inc. Improving Muscular Strength and Endurance