OVERTRAINING IS EVIDENCED BY EARLIER OVERUSE OF AEROBIC RESOURCES
Bishop, D., De Vrijer, A., & Russell, S. (2009). Earlier task failure following overtraining is not associated with the earlier accumulation of maximal levels of blood lactate. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.
This study investigated why overtraining limits performance by looking at potential mechanisms including an increase in metabolic end products such as lactate, earlier attainment of VO2peak, and an increased “sensation” of fatigue. Males (N = 18) performed a graded exercise test to determine VO2peak and the lactate threshold. Time-to-fatigue at 20% of the difference between VO2peak and the lactate threshold was also assessed. Ss were then matched and randomly assigned to either a control or training group. Those assigned to the training group completed high-intensity training twice a day, seven days per week for up to three weeks. A time-to-fatigue test replaced one of the training sessions every second day. Training continued until time-to-fatigue decreased to 75% of the Day 1 time. VO2, blood lactate, and rating of perceived exertion were determined at 75 and 100% of time-to-fatigue on Day 1, and at 100% of time-to-fatigue for all subsequent tests.
Time-to-fatigue was not significantly different between groups at baseline but was significantly different at the final time-to-fatigue test. For the training group, blood lactate measured at fatigue during the final time-to-fatigue test was not significantly different from the blood lactate measured at 75% of time-to-fatigue on Day 1, but was significantly less than that measured at 100% of time-to-fatigue on Day 1. However, in the training group, both endVO2 and rating of perceived exertion during the final time-to-fatigue test were significantly greater than the values recorded at 75%, but not 100%, of time-to-fatigue on Day 1.
Implication. High-intensity training results in significant performance decrements as assessed by the time-to-fatigue test. Earlier task failure is not associated with the earlier accumulation of maximal levels of blood lactate. Fatigue is not related to muscle lactate levels. However, earlier task failure is associated with the earlier attainment of VO2peak and the earlier sensation of fatigue.
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