What distinguishes functional overreaching from overtraining syndrome?

Functional overreaching and overtraining syndrome are both related to an athlete's training load and recovery, but they differ in terms of performance changes and duration.

In functional overreaching, the key characteristic is a short-term decrease in performance due to an increase in training intensity or volume without adequate recovery. This temporary decline is often followed by a rebound effect known as supercompensation, where performance improves in the long term after recovery. Athletes may experience fatigue, but with proper rest and nutrition, they can quickly return to and even surpass their previous performance levels.

In contrast, overtraining syndrome is characterized by a long-term decrease in performance that persists despite recovery efforts. This condition can lead to chronic fatigue, mood disturbances, and various physiological issues, requiring a significantly longer period for recovery.

Thus, the distinguishing factor for functional overreaching is the transient, short-term decrease in performance, making it differentiable from the more severe and prolonged effects seen in overtraining syndrome.