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Guy Boos KIN 470 12 11 15 Lab 6 INTRODUCTION Muscular strength and the magnitude of the force it produces is dependent on how large the cross section of the muscle is About 2 3 of muscular strength comes from the size of the muscle which also correlates to how large the cross section is The larger the cross section the more sarcomeres which are the contracting unit of a muscle fiber With a larger amount of sarcomeres present the more force that can be produced It is important to note that when comparing the muscular force production of males to females males produce more force due to the presence of testosterone which is the hormone that promotes muscle growth Muscular force is created when muscles contract Contractions occur when actin and myosin bind and creating tension within the muscle Actin and myosin are proteins that are found within myofibrils which are rod shaped muscle fibers The myofibril contains two types of fibers thick which are composed of myosin and thin which are composed of actin The presence of calcium is what creates these contractions and until calcium is present contractions will continue to occur When muscles are contracted for a prolonged period of time or repeated contractions they begin to fatigue Fatigue occurs when a build up of pH or hydrogen ions and inorganic phosphate accumulate in the muscle The increase in pH is detrimental to producing contractions because the increase in Hydrogen ions creates competition at the binding site of troponin with calcium This competition creates a decrease in contraction because if calcium doesn t bind with troponin then cross bridges do not form Inorganic phosphate is formed when adenosine diphosphate is bonded with phosphate The build up of inorganic phosphate moved from the myofibril into the sarcoplasmic reticulum which the precipitates and creates salt which inhibits the abilities of the muscle to contract Their endurance during these contractions is dependent on the type of muscle fiber being