What is a common sign of muscle fatigue?

A common sign of muscle fatigue is indeed decreased force production and difficulty completing repetitions. When muscles become fatigued, their ability to generate force diminishes, which directly impacts performance in strength and endurance activities. This fatigue can manifest as an inability to lift the same weight or perform as many repetitions as previously achieved.

As muscles tire, factors such as the accumulation of metabolic byproducts, depletion of energy stores, and changes in muscle fiber recruitment contribute to this decrease in performance. Therefore, when an individual feels that they can no longer exert the same effort or struggle to finish a set, it signals that fatigue has set in.

The other options reflect states that are typically associated with well-rested and well-hydrated muscles rather than fatigue. For instance, increased energy levels and improved motivation are indicators of readiness and well-being, not fatigue. Enhanced endurance during prolonged activities suggests that a person is in a condition of peak performance, contrary to what is observed during muscle fatigue. Lastly, better recovery times indicate that the muscles are recovering effectively, hinting at a lack of fatigue rather than the presence of it.