During prolonged exercise, which factor contributes to a decrease in muscle efficiency?

A decrease in muscle efficiency during prolonged exercise is primarily associated with fatigue-induced muscle soreness. When muscles are engaged in continuous or intense activity, they can experience a buildup of metabolic byproducts, such as lactic acid, which contributes to soreness and fatigue. This sensation can inhibit the muscles' ability to contract effectively, leading to decreased performance.

Moreover, when muscle fibers are repeatedly stressed, they can undergo microscopic damage, resulting in inflammation and soreness, which further impairs efficiency. The body's ability to perform tasks at optimal levels diminishes as these factors develop, making it more challenging to sustain vigorous exercise.

Conversely, the other factors listed would generally support muscle efficiency rather than decrease it. Increased hydration helps maintain cellular function and performance, high levels of ATP are essential for muscle contraction, and rest periods enable recovery and can enhance overall workout efficiency.