Hedelin, R., Kentta, G., Wiklund, U., Bjerle, P, & Henriksson-Larsen, K. (2000). Short-term overtraining: Effects on performance, circulatory responses, and heart rate variability. Medicine and Science in Sports and Exercise, 32, 1480-1484.

Elite athletes (canoeists; N = 9) volunteered for this training study. They participated in a 6-day training camp where the training load was approximately 50% greater than normal. Activities included endurance cross-country skiing (65%), strength training (10%), and high-intensity/anaerobic training (25%).

The athletes' performance and physiological markers declined over the short camp-period. Run time to exhaustion worsened, and heart rates at all workloads, VO2max, and Lamax decreased significantly. Plasma volume increased. No changes in high or low frequency heart rate variability were observed. The pattern of responses suggested that alterations were peripherally mediated rather than being centrally determined.

Implication. Fatigue from excessive training loads (overreaching) is likely to be peripheral in nature rather than caused by central circulatory factors.

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