Which symptom could indicate both overreaching and overtraining?

Depression is a symptom that can manifest in both overreaching and overtraining, making it the correct choice in this context. Overreaching is characterized by a temporary state of excessive training without sufficient recovery, leading to a drop in performance and possible mood disturbances, including feelings of depression. If this state persists without adequate rest, it can progress to overtraining syndrome, where symptoms become more severe, also including notable mood disturbances such as depression.

In contrast, muscle pain, while a common symptom of both conditions due to increased physical demand, is not specific enough to clearly indicate one or the other. Increased performance would typically not be associated with either overreaching or overtraining; instead, these conditions often lead to decreased performance. Weight gain can also occur due to a variety of factors and may not directly indicate either state, as it can occur for reasons unrelated to performance or overtraining, such as changes in dietary habits or hormonal fluctuations.

Therefore, depression stands out as a shared symptom that specifically links both overreaching and overtraining, highlighting the importance of mental health in the context of athletic performance and recovery.