Which of the following is a sign of overtraining?

Increased fatigue is indeed a sign of overtraining. Overtraining occurs when the training intensity and volume exceed the body's ability to recover, leading to physical and psychological symptoms. One of the primary indicators of overtraining is a state of chronic fatigue that persists despite adequate rest and appropriate training loads. Athletes may experience an unusual level of tiredness that does not respond to rest, indicating that their body is struggling to cope with the demands placed upon it.

In this context, improved performance, enhanced motivation, and reduced training load typically represent positive training adaptations rather than signs of overtraining. Improved performance suggests that the athlete is responding well to their training, while enhanced motivation indicates a positive psychological state conducive to training. A reduced training load may be a response to rest and recovery rather than a symptom of overtraining, as athletes often adjust their loads to avoid fatigue or injury. Therefore, among the provided options, increased fatigue stands out as a clear indication of overtraining, highlighting the need for athletes to monitor their physical and mental states closely.