Examine your graph and the data in Table 1. What conclusion can you draw about the number of individual muscle fibers that are firing in the last 10 s compared with the first 10 s?
Human Physiology with Vernier17 - 11Grip Strength and Muscle Fatigue2.
Is the change in number of muscle fibers that contract occurring at a constant rate?3.Use your knowledge of fast, slow, and intermediate skeletal muscle fibers to hypothesize which fibers are contracting in the first, third, and final 10 s intervals.4.How might you explain the subject’s response to coaching? This should be evident in the last10 s of data for Parts I and II of the exercise. Discuss the possible involvement of the central nervous system, in addition to the muscle fibers.5.Compare the slopes recorded in Table 3. Give a possible explanation for the difference, if any, in muscle fatigue rates seen in continuous versus repetitive gripping.
Human Physiology with Vernier17 - 12LabQuest18EMG and Muscle FatigueVoluntary muscle contraction is the result of communication between the brain and individual muscle fibers of the musculoskeletal system. A thought is transformed into electrical impulses which travel down motor neurons (in the spine and peripheral nerves) to the neuromuscular junctions that form a motor unit (see Figure 1).The individual muscle fibers within each motor unit contract with an “all or none” response when stimulated, meaning the muscle fiber contracts to its maximum potential or not at all. The strength of contraction of a whole muscle depends on how many individual fibers are activated, and can be correlated with electrical activity measured over the muscle with an EMG sensor.Regular exercise is important for maintaining muscle strength and conditioning. The most common form of non-aerobic exercise is isotonic(weight training). In isotonic exercise, the muscle changes length against a constant force. In isometricexercise the length of the muscle remains the same as greater demand is placed on it. An example of this is holding a barbell (or suitcase) in one position for an extended period of time. Muscle fatigue occurs with both forms of exercise.In this experiment, you will use a Vernier Hand Dynamometer to measure maximum grip strength and correlate this with electrical activity of the muscles involved as measured using the Vernier EKG Sensor. You will see if electrical activity changes as a muscle fatigues during continuous maximal effort. Finally, you will observe the results of a conscious effort to overcome fatigue in the muscles being tested.Figure 1Important: Do not attempt this experiment if you suffer from 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.
Human Physiology with Vernier17 - 13Grip Strength and Muscle FatigueOBJECTIVESIn this experiment, you willObtain graphical representation of the electrical activity of a muscle.