UMass Amherst KIN 470 - docx (7 pages)

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Pages:
7
School:
University of Massachusetts Amherst
Course:
Kin 470 - Exercise Physiology

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INTRODUCTION Muscle strength endurance and fatigue are all very highly studied areas of exercise physiology Muscle strength is defined by the ability to produce force Muscular endurance is defined by the ability of a muscle or groups of muscles to continuously exert force against resistance or an object for a period Muscle fatigue is defined as the decline in ability of a muscle to produce force A muscle can produce force due to a process called excitation contraction coupling Excitation contraction coupling is when electrical stimulus is converted into a mechanical response For example an action potential in skeletal muscle triggers muscle contraction A common way to examine muscle activity is by use of electromyography EMG EMG is a way to record electrical activity of muscles that is converted into a visual image that can be interpreted This lab uses surface EMG which requires electrodes to be placed on the surface of the skin to record activity Maximal voluntary contraction or maximal force varies between individuals The reason behind this is because of the size principle The size principle states that motor units are recruited from smallest to largest based on force needed For small forces small motor units are recruited to fire For large forces large motor units are recruited When intensity increases rate coding occurs which is when the neurons fire more rapidly Someone who produces a large force uses large motor units and the neurons fire rapidly to sustain the large force Someone who produces a small force uses small motor units and the neurons don t fire as rapidly METHODS The first part of this lab was to obtain maximal voluntary contraction for each subject There were 15 college aged subjects who participated in this study 4 males and 11 females A hand grip dynamometer was connected to a computer which had a biopac program used to record force Before the lab began the hand grip dynamometers were calibrated Each subject took turns holding the hand grip



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