Billat, V. L., Flechet, B., Petit, B., Muriaux, G., & Koralsztein, J-P., (1999). Interval training at VO2max: Effects on aerobic performance and overtraining markers. Medicine and Science in Sports and Exercise, 31, 156-163.

The influence of a defined increase in training volume at vVO2max on aerobic performance, noradrenaline, and heart rate was investigated.

Ss (N = 8) followed four weeks of normal training. One session per week was at vVO2max, comprising five repetitions run at 50% of the time that could be performed to maximum at vVO2max pace, each followed by recovery running at 60% of vVO2max. A further four weeks of "overload" training was performed with the number of vVO2max sessions being increased to three per week.

vVO2max training improved running velocity associated with VO2max. Running economy increased but VO2max did not change. Time to exhaustion at vVO2max did not change nor did distance run at vVO2max. Overload training changed neither the performance nor the factors concerning performance. Submaximal heart rate decreased, and plasma norepinephrine at the end of a test effort increased, after overload training.

These minimal changes suggest that the increased training load was not heavy enough to induce overtraining in the relatively short period of observation.

Implication. Moderate increases in workload do not necessarily induce overtrained states.

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