Halson, S. L., Bridge, M. W., Gleeson, M., Meeusen, R., & Jeukendrup, A. E. (2002). Time course of performance changes and markers of overreaching in cyclists. Medicine and Science in Sports and Exercise, 34(5), Supplement abstract 1536.

Endurance cyclists (N = 8) were systematically monitored and controlled for six weeks: two weeks of normal training, two weeks of intensified training, and two weeks of recovery training. Performance was assessed over 20 days with a 40-km time trial, a high-intensity exercise test, and a VO2max test.

During intensified training, maximum power output declined at the end of the time trial and at the end of the VO2max test. Global mood scores increased 29% during the same period. Decreased performance coincided with a 9.3% decrease in maximum heart rate and a 14% reduction in maximal plasma lactate. RPE increased for standardized submaximal work. No changes were observed in blood parameters, substrate utilization, cycling efficiency, or resting blood factors. These changes and evidence of overreaching were not obvious until day 7 of intensified training.

Implication. Excessive increases in training intensity can be tolerated for a short period of time before performance and psychological factors deteriorate and become noticeable. Performance and psychological disruptions precede physiological changes.

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