Grip Strength and Muscle Fatigue..pdf - Lab 5 Grip Strength and Muscle Fatigue Skeletal muscle is composed of bundles of individual muscle fibers(see

Grip Strength and Muscle Fatigue..pdf - Lab 5 Grip Strength...

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Human Physiology with Vernier Biol 104 Spring 2019 Lab 5: Grip Strength and Muscle Fatigue Skeletal muscle is composed of bundles of individual muscle fibers (see Figure 1) and has unique properties which allow it to respond to stimuli by contracting. Each muscle is composed of many motor units. A motor unit is defined as an individual motor neuron (signal from the brain/spinal cord) and the muscle fibers that neuron innervates (controls). Motor units can consist of 1 motor neuron innervating several muscle fibers or 1 motor neuron innervating hundreds to thousands of muscle fibers. The muscles that are under the finest neuronal control are those that have many small motor units. Individual motor units respond to a stimulus (e.g., nerve impulse) with an all or none response, meaning the muscle fibers in the motor unit either contract to their maximum potential or do not contract at all. The strength of contraction of a whole muscle is dependent on the number of motor units activated and contracting. The stronger the contraction the greater number of motor units called upon to contract to their maximum potential, a process called recruitment. Once a muscle has contracted, relaxation must occur before the muscle can contract again. There are three basic types of muscle fibers: slow fibers, fast fibers, and intermediate fibers . Fast fibers contract quickly but for a relatively short duration. Slow fibers respond less rapidly, but are capable of a more sustained contraction. Muscle fatigue occurs with a prolonged or repetitive use of a muscle group, and is familiar to anyone who has ever carried a heavy suitcase or walked up a long flight of stairs. With fatigue, there is a sense of weakness and even discomfort, which eventually leads one to discontinue the activity that is causing it. The mechanism of fatigue is multifactorial and not fully understood, but is felt to involve the central nervous system, peripheral nervous system, muscle units and individual muscle fibers. At the level of muscle cells, depletion of energy stores may be important. Regular exercise improves muscular function and delays the onset of fatigue, thus increasing the amount and duration of work that can be performed. Exercise is important for optimal athletic performance, prevention of injury in athletes and non-athletes, and the maintenance of good general health. In this experiment, you will examine the effect of fatigue on muscle action by performing sustained and repetitive isometric contractions of muscles of the arm and hand using a Vernier Hand Dynamometer. Figure 1
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