Overtraining
Overtraining syndrome is a prolonged decline in performance, lasting weeks to months, caused by an imbalance between training stress and recovery. It sits at the far end of a spectrum that starts with normal, short-term overreaching.
Overreaching versus overtraining
Functional overreaching — a hard block that leaves you tired for days — is a normal part of training and is followed by improvement. Non-functional overreaching lasts weeks without a performance gain. Overtraining syndrome is the extreme, and recovery can take months.
Warning signs
Watch for performance falling despite training, persistent fatigue, poor sleep, low mood or irritability, frequent illness, a resting heart rate above your normal and HRV below your baseline. If several appear together, cut back and see a doctor to rule out other causes such as illness or low energy availability.