Final answer:
Low-Frequency Fatigue is a form of muscle fatigue resulting from mechanical and metabolic factors, involving depletion of ATP reserves and lactic acid buildup, which affects muscle function. ATP is necessary for muscle contraction, and its depletion leads to muscle fatigue, especially after intense or prolonged activities.
Step-by-step explanation:
Low-Frequency Fatigue (or mechanico-metabolic fatigue) refers to muscle fatigue that results from a combination of mechanical and metabolic factors, as outlined in choice c). This condition is a form of muscle fatigue, which occurs when a muscle can no longer contract despite receiving signals from the nervous system. During muscle contraction, ATP is essential, and as ATP reserves are depleted, muscle function declines. This depletion is more significant during brief, intense activities rather than sustained, lower intensity efforts. Lactic acid buildup, which occurs during intense exercise, may also contribute to fatigue by lowering intracellular pH and affecting enzyme and protein activity.
Additionally, imbalances in Na+ and K+ levels caused by membrane depolarization can disrupt Ca++ flow out of the sarcoplasmic reticulum (SR), and extended periods of exercise may damage the SR and the sarcolemma, leading to impaired Ca++ regulation. When discussing muscle fibers and their resistance to fatigue, slow oxidative (SO) fibers use aerobic metabolism for longer, low-power contractions and are slow to fatigue, whereas fast glycolytic (FG) fibers, which rely on anaerobic metabolism, create powerful contractions but fatigue quickly.