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1.65–1.73 m (5’5”−5’8”)1.75–1.83 m (5’9”−6’)1.85 m (6’1”) and aboveTable 5−Individual Pinch Strength Data
Human Physiology with Vernier16 - 5Grip Strength ComparisonMean force (N)Dominant hand index fingerDominant hand middle fingerDominant hand ring fingerDominant hand little fingerGrip Strength and Muscle FatigueSkeletal 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. Individual muscle fibers respond to a stimulus (e.g., nerve impulse) with an all or none response, meaning the muscle fiber contracts to its maximum potential or not at all. Once a muscle has contracted, relaxation must occur before it can contract again. There are three basic types of muscle fibers: slow fibers, fast fibers, andintermediate fibers. Fast fibers contract quickly but for a relatively short duration. Slow fibers respond less rapidly, but are capable of a more sustained contraction. The strength of contraction of a whole muscle is dependent on the number of muscle fibers involved.Muscle fatigue occurs with 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 theactivity 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 Figure 1
16 - 6Human Physiology with VernierLabQuest 16athletic 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.Important: Do not attempt this experiment if you have arthritis, or other conditions of the hand, wrist, forearm, or elbow. Inform your instructor of any possible health problems that might be exacerbated if you participate in this exercise.OBJECTIVESIn this experiment, you willObtain graphical representation of the force exerted by your hand while gripping.Observe the change in hand strength during a continuous grip over time.Observe the change in hand strength during rapid, repetitive gripping.PROCEDURESelect one person from your lab group to be the subject.