Overtraining syndromeOTS · Unexplained underperformance syndrome

Overtraining syndrome is a state of long-term performance decline that does not resolve with a normal rest period, taking weeks to months to recover from. It is distinct from functional overreaching — a deliberate short-term overload followed by a rebound — and from non-functional overreaching, which sits between the two.

It matters because it is genuinely serious and genuinely rare. True OTS involves persistent fatigue, mood disturbance, disturbed sleep, raised resting heart rate, frequent illness and a stubborn loss of performance. Most people who say they are overtrained are under-recovered, under-slept or under-fed instead.

In practice there is no single diagnostic test — it is a diagnosis of exclusion, made after ruling out anaemia, thyroid problems, infection and low energy availability. Prevention is monitoring: tracking load, sleep, resting heart rate and HRV, and scheduling deloads before you need them.