HSS 388 Lecture 1: Review Chapters 1 and 2

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University of Louisville
Health and Sport Sciences
HSS 388
Elizabeth Ledford

Chapter 1 & 2 Review • Contraction of Myofibril o I and A band will not overlap if muscle is over stretched o I and A band must be overlapped for crossbridge to form o When bands are overlapped there is very little force potential o 100-120% resting length most optimum overlap o A-band/H-zone are thick filament and I-band/Z-line are thin filament • Muscular System Key Points o The number of crossbridges formed between actin and myosin at any time dictates the force production of a muscle o Less protein there is the less crossbridges formed o Relaxation requires ATP • Neuromuscular System Key Point o All or nothing principle – you cannot work one part of your muscle, either it all works or none works o It hits threshold or it does not • Stimulated Motor Unit o Fused tetanus – how we interact with the environment • Muscular Fiber Characteristics o Type 1 – low threshold; small diameter; aerobic; red (high blood supply); use oxygen; slow twitch; smaller neurons o Type 2 – high threshold; large diameter; anaerobic; easy to exhaust; whitish pink color; does not use oxygen; fast twitch; very inefficient o Type 2x – thresholds drop; can be recruited with training; strongest; fastest; most powerful; most anaerobic o Most athletes use type 2 • Motor Unit Recruitment o The force output of a muscle can be varied through change in the frequency of activation of individual motor units ▪ Run faster – more force ▪ Run slower – less force ▪ Increase frequency of motor units ▪ Increase # of total motor units o What recruitment patterns are happening during a graded- exercise test like the Bruce treadmill protocol for VO2max? ▪ Starts with walking low force as grade increases force increases and as force increases more motor units are required; recruiting more • Proprioception o Muscle spindles – stretch reflex, extends quick stretch, excites a contraction o GTO reflex – tension, inhibition contraction, measures tension throughout tendon • Application of Science in Training o Increases in a
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