UMass Amherst KIN 470 - Lab 6 Handout_adjusted (5 pages)

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Lab 6 Handout_adjusted



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Lab 6 Handout_adjusted

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Pages:
5
School:
University of Massachusetts Amherst
Course:
Kin 470 - Exercise Physiology

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LABORATORY 6 MUSCLE STRENGTH ENDURANCE FATIGUE IMPORTANT TERMS 1 2 3 4 5 6 7 Muscle strength Muscle fatigue Muscle endurance Excitation Contraction Coupling EMG Recruitment Rate coding IMPORTANT CONCEPTS 1 Factors determining muscle strength 2 Muscle fatigue induced by repetitive isometric contractions 3 Units of measurement for muscle strength 4 Size principle intro paragraph INTRODUCTION Muscle strength is the ability generate force This is dependent on the cross sectional area of the muscle Thus a larger muscle will be able to produce more force The larger the muscle the more sarcomeres exist in parallel Each group of sarcomeres in series generate some amount of force so the more sarcomeres in parallel the more force can be generated Muscular endurance is the ability of a muscle or group of muscles to sustain repeated contractions against a resistance or sustain a force for an extended period of time Muscular endurance is quite different than muscular strength as endurance measures how long a person can maintain a submaximal force while strength measures how much force a person can produce One major physiological difference between endurance and strength is fiber type Type I fibers are more fatigue resistant than type II fibers because they contain greater amounts of myoglobin mitochondria and blood capillaries In this lab we will examine fatigue during a muscle endurance test using force and EMG measurements Muscle fatigue is defined as a decline in maximal force production and affects the ability to do work Muscle fatigue can occur in response to short term high intensity exercise or prolonged submaximal exercise The mechanisms underlying muscle fatigue are multifactorial and may be dependent on the type of exercise and the mode of contraction performed Muscle fatigue can occur as a result of alterations in any step along the force producing pathway The central nervous system may play a role in muscle fatigue by altering the neural drive from the motor cortex to the muscle cell This would be evident as 1 a reduction in the number of functioning motor units or 2 a reduction in motor unit firing rate This is referred to as central fatigue The term peripheral fatigue refers to factors associated with inhibition of excitation contraction coupling These factors may affect the propagation of the action potential across the neuromuscular junction along the sarcolemma and the transverse tubular system This may in turn affect the release of calcium from the sarcoplasmic reticulum SR to the cytosol which is critical for cross bridge formation When energy needs cannot be met by aerobic metabolism and stores of phosphocreatine become depleted inorganic phosphate Pi and H start to accumulate These bi products of anaerobic metabolism have shown to inhibit maximal force production along with reduced release of calcium from the SR MUSCLE CONTRACTIONS The body is able to produce movement by means of muscle contractions Muscle contractions occur when tension



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