Overtraining syndrome

Overtraining syndrome (OTS) sits on a continuum with functional overreaching (FOR) and non-functional overreaching (NFOR), per ECSS/ACSM consensus. It is a maladaptive state in which prolonged training load exceeds recovery capacity, causing unexplained performance decline over weeks to months alongside fatigue, mood disturbances, and sleep disruption. Downward HRV trends, rising resting heart rate, and disproportionate RPE for a given workload are commonly observed but non-specific, and parasympathetic indices may paradoxically rise rather than fall in some athletes.