The present research was designed to evaluate the adaptive responses to oxidative stress and inflammation in handball players subjected to well-controlled training intervals over one-year of competition. Seven blood samples were collected over the season of the study, approximately one a month. Plasma lipid peroxidation, nitrite, cytokines (IL-1β, IL-6, INFγ and TNFα), and the glutathione cycle in erythrocytes, were measured. Exercise intensity, measured with the Borg's scale, increased significantly up to the middle of the competition season, coinciding with maximal creatine kinase and lactate dehydrogenase values, and then decreased at the end of the study. The inflammatory markers including nitrite, IL-1β, IL-6, and, to a lesser extent INFγ, increased early in the training season, and remained elevated until the end of the study. TNFα, however, remained low during the season. The oxidative stress response included a transient increase of the glutathione disulphide/glutathione ratio and glutathione reductase activity at the beginning of the study, returning to basal values somewhat later. Glutathione peroxidase also increased at the end of the training season, and lipid peroxidation levels remained low during the athletic season. These results suggest that well-trained athletes were best adapted to the oxidative response, although the beneficial effects of some of the inflammatory cytokines on skeletal muscle myogenesis and repair cannot be ruled out.

The aim of this study was to investigate whether different phases of training affect oxidative stress and antioxidant defences in professional cyclists. Ten professional cyclists, aged 21.8 ± 2.5 years, were enrolled in the study. They were classified into two groups of five athletes each one with similar nutritional intake excepting for the overload of vitamin C (1000 mg day(-1)) and E (400 mg day(-1)) supplementation in one of them. The cyclists of both groups performed the same exercise design, consisting of hard, tapering and recovery training periods. Total antioxidant capacity (TAC) of the diet, plasma oxygen radical absorption capacity (ORAC), lipid peroxidation (LPO), DNA damage (8-OHdG) and erythrocyte glutathione disulfide/glutathione ratio (GSSG:GSH(-1)) were measured. During the intense exercise trainings, the cyclists without vitamin supplements had the TAC of diet significantly lower than the supplemented group. Plasma ORAC, LPO and 8-OHdG were similar in both groups of athletes. Athletes with supplements had a basal LPO:ORAC(-1) ratio lower than that without supplements, but this ratio converged to the same level at the end of the training in both groups of cyclists. Both groups of cyclists showed similar changes in GSSG:GSH(-1) ratio and in GSSG and GSH levels along the study. The data suggest that well-trained athletes with suitable ultra-endurance training volume and intensity do not require antioxidant vitamin supplements to adapt their endogenous antioxidant defenses to exercise-induced ROS.