Which of the following factors is NOT a contributor to muscle fatigue?

Excessive oxygen availability does not contribute to muscle fatigue; in fact, it typically supports sustained muscle activity. When oxygen is plentiful, muscles can effectively carry out aerobic metabolism, allowing for prolonged energy production with minimal fatigue. This maximizes ATP generation, which is essential for muscle contraction and overall performance.

In contrast, factors like a shortage of ATP and the accumulation of lactic acid are well-known contributors to muscle fatigue. A lack of ATP directly affects muscle fiber contraction since ATP is crucial for muscle function and relaxation. Similarly, lactic acid accumulation can alter the pH within muscles, impacting their ability to contract effectively. The accumulation of extracellular potassium can also lead to muscle fatigue due to its role in generating action potentials, affecting the excitability of muscle fibers. Therefore, it's the availability of oxygen that plays a supportive role in muscle function rather than contributing to fatigue.