PHYS ED 32 Lecture Notes - Lecture 4: Heredity, Bench Press, Motor Unit

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24 Oct 2013
Lecture 4:
Muscular Strength: usually assessed by measuring the maximum amount of weight a
person can lift one time. e.g. taking 1 RM for the bench press
Muscular Endurance: usually assessed by counting the maximum number of
repetitions of a muscular contraction a person can do (e.g. push-ups) or the maximum
amount of time a person can hold a muscular contraction. e.g. curl-up test, push-up test,
squat endurance test
Benefits of Muscular Strength and Endurance:
Improved performance of physical activities
Injury prevention
Improved body composition
Enhanced self-image and quality of life
Improved muscle and bone health with aging
Prevention of chronic disease
Skeletal Muscle Tissue
muscle fascicle (bundle of fibers) muscle fiber (all) myofibril
Sarcomere basic unit of muscle; composed of long, fibrous proteins that slide
past each other when the muscles contract and relax
o Protein filaments
o Sliding filaments
o Theory: filaments slide and contract when energy is used
Myosin and Actin
o Muscle proteins responsible for elastic and contractile properties of
Basic Muscle Physiology
Hypertrophy: larger size of individual muscle fiber (via lifting, working out)
Atrophy: muscle gets small and shriveled
Slow Twitch (endurance athletes) vs. Fast Twitch (sprinters)
Slow Twitch
o Resist fatigue
o Don’t contract as rapidly and forcefully as fast twitch fibers
o Rely primarily on the aerobic energy system
Fast Twitch
o Fatigue more quickly than slow-twitch fibers
o Contract rapidly and forcefully
o Rely more on the anaerobic energy system
Typical Muscle Fiber Composition in Elite Athletes
% Slow Fibers
% Fast Fibers
Type I
Types IIx and IIa
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