What does "overtraining" refer to in a fitness context?

In the context of fitness, "overtraining" specifically refers to the condition where an individual has pushed their training beyond their body's ability to recover, leading to physical and mental fatigue. When the training volume or intensity surpasses the capacity of the body to recuperate, athletes or fitness enthusiasts may experience performance declines, increased soreness, irritability, lethargy, and other symptoms indicating that their body is not coping well with the stress of the training regimen. This highlights the importance of balancing training with adequate rest and recovery to prevent such negative outcomes and ensure consistent progress.

The other options do not capture the essence of overtraining. Training with insufficient intensity does not lead to the adverse effects associated with overtraining; instead, it might prevent improvement. A period of recovery is essential for adaptation and does not constitute overtraining. Continuous improvement in performance implies that the training is effectively managed, which is contrary to the concept of overtraining.