# Overtraining syndrome

Overtraining syndrome (OTS) sits on a continuum with functional overreaching (FOR) and non-functional overreaching (NFOR), per the ECSS/ACSM consensus. It is a maladaptive state where your training load outstrips your recovery for too long. The hallmark is an unexplained drop in performance over weeks to months. It comes with fatigue, mood disturbances, and disrupted sleep. Some signs are common but non-specific: a downward HRV trend, a rising resting heart rate, and a workout feeling harder than it should (a high RPE for the load). And in some athletes, parasympathetic markers paradoxically rise rather than fall.

## Sources

- Meeusen R, Duclos M, Foster C, et al.. (2013). Prevention, Diagnosis, and Treatment of the Overtraining Syndrome: Joint Consensus Statement of the European College of Sport Science and the American College of Sports Medicine. Medicine & Science in Sports & Exercise. https://doi.org/10.1249/MSS.0b013e318279a10a

---

_Canonical: https://longevity-switzerland.com/en/glossary/overtraining-syndrome · Part of Longevity Cities · Updated 2026-06-22_