Vollaard, N. B., Shearman, J. P., & Cooper, C. E. (2004). The oxidative stress response to exercise is unchanged after tapering, but antioxidant defenses are improved. Medicine and Science in Sports and Exercise, 36(5), Supplement abstract 1765.

Tapering has been demonstrated to be an effective way of enhancing performance after a period of intensive training. However, the mechanism for the ergogenic effect is unknown. It was hypothesized that overloaded training increases resting levels of oxidative damage through an additive effect of repeated high-intensity exercise, whereas tapering may alleviate oxidative stress and improve the antioxidant defense system (p. 258). This study determined the oxidative stress response to overloaded training and tapering. Well-trained endurance athletes (N = 9) performed two consecutive four-week periods of training in a crossover design. Each period included a two-week build-up phase followed either by an additional two weeks training at the same constant load (control), or by a week of overloaded training preceding a one-week taper. Training impulse (TRIMP) was increased by 40% during overloaded training, and decreased by 60% during tapering. Performance was monitored through weekly performance trials, consisting of 45 min cycling at 70% of Wmax followed by a 15-minute time-trial. Blood samples were taken before and after the last three performance trials of each four-week section, and analyzed for oxidatively modified heme (OxH), reduced glutathione (GSH), and oxidized glutathione (GSSG).

Combined data of the performance trials indicated an exercise-induced increase in levels of OxH and GSSG, and a decrease in GSH and GSH/GSSG. Tapering was shown to significantly increase performance (+4.7%) and was associated with an increase in resting GSH levels. Training modifications did not influence exercise-induced changes in markers of oxidative stress. Tapering may enhance the antioxidant defense system, but does not seem to reduce exercise-induced oxidative damage to hemoglobin. It is unclear whether the performance enhancing effect of tapering is reliant to an extent on changes in antioxidant status and oxidative damage.

Implication. Tapering increased performance and improved antioxidant defenses.

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