Question

Research indicates that following a series of voluntary contractions to produce skeletal muscle fatigue, electrical stimulation of the "fatigued" muscle group results in an increase in the maximal voluntary force production. This experiment suggests that:

a. None of these answers is correct.
b. exercise-induced muscle fatigue results from peripheral factors located within the muscle.
c. exercise-induced muscle fatigue results from peripheral factors located at the neuromuscular junction.
d. the upper limit of voluntary strength is psychologically set and that the central nervous system can limit performance.

Answer 1

Muscle fatigue occurs when a muscle can no longer contract in response to signals from the nervous system. Factors such as reduced ATP reserves, lactic acid buildup, and imbalances in Na+ and K+ levels can contribute to muscle fatigue. Long periods of sustained exercise may also lead to damage in the SR and sarcolemma.

Step-by-step explanation:

Muscle fatigue occurs when a muscle can no longer contract in response to signals from the nervous system. The exact causes of muscle fatigue are not fully known, although certain factors have been correlated with the decreased muscle contraction that occurs during fatigue. ATP is needed for normal muscle contraction, and as ATP reserves are reduced, muscle function may decline. This may be more of a factor in brief, intense muscle output rather than sustained, lower intensity efforts. Lactic acid buildup may lower intracellular pH, affecting enzyme and protein activity. Imbalances in Na+ and K+ levels as a result of membrane depolarization may disrupt Ca2+ flow out of the SR. Long periods of sustained exercise may damage the SR and the sarcolemma, resulting in impaired Ca regulation.