exert its maximal Textbook, page 13. \\'hen a muscle is stretched or-shortened, the length of each individual sarcomere also increases or decreases, respectively. Within the range of sarcomere lengths there is an optimal length at which provides for the greatest possible number of cross-bridge formations. Longer or shorter than this optimal length, the number of cross-bridge formations is reduced and thus active force production is reduced. Muscles must be stretched from their resting length for most effective action. Example - flexing the knee, hip, and ankle joints before jumping. In a movement such as vertical jumping, preparatory counter movement shifts the force-velocity curye to the right, thus causing the leg extensor muscles to exert much higher forces at any angular velocity of the knee in the concentric phase. The enhancement of performance in this "stretch-shortening" cycle can be attributed to restitution of elastic energy and stretch reflex potentiation of muscle. Figures 11-4 and 11-5 in Laboratory
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