Overtraining can be called as an imbalance of training stress and recovery. That is too much training (and all other possible stressors like work, family, time lag etc.) followed by too little recovery that will result in decreased adaptation state.
Jarek Mäestu (PhD, Sports Sciences) - Researcher at Sportlyzer Rowing Academy. He also works as a researcher and gives lectures on coaching sciences in the University of Tartu.