Seasonal Longitudinal Study of Oxidative Stress and Redox Status in Professional Athletes of Different Sports

Abstract

It is well established that physical exercise induces reactive oxygen species production, while physical training increases antioxidant defense systems thereby reducing exercise-induced oxidative stress. However, intense physical exercise, competition, and training such as those imposed on high-level athletes may lead to increased oxidative stress implicating an overtraining condition. In the present study, the effects of training and competition load on oxidative stress, redox and antioxidant status, and cell damage markers have been studied on high-level players in different sports (i.e., 15 ultra-endurance and 12 long-distance runners, and 12 junior professional rugby players) during a competitive season. Oxidative damage plasmatic markers, including protein carbonyls (PC) and thiobarbituric acid-reactive substances (TBARS), total antioxidant capacity (TAC), and amino-thiols redox status were assessed at three critical time points of the season: T0, the beginning; T1, the top; T2, the end. Seasonal variations of all the investigated parameters were observed. With respect to the basal level T0 (0.69 ± 0.14), significant increases of PC concentration (nmol/mg protein) at T1 (1.08 ± 0.36, p < 0.001) and T2 (1.04 ± 0.27, p < 0.01), as well as of TBARS concentration (µM, T0: 6.11 ± 1.11) at T2 (8.09 ± 1.07, p < 0.0001) and T1 (6.77 ± 1.22, p < 0.01) were measured in ultra-endurance athletes. PC was found significantly increased in rugby players too (T0: 0.76 ± 0.26 vs. T2: 1.19 ± 0.34; p<0.05). With regard to the oxy-redox status, TAC activity was not found significantly changed during the monitored time period, while amino-thiols redox status was upregulated, as demonstrated by the increase of oxy and total glutathione (GSH) and cysteine (Cys) concentrations, particularly in ultra-endurance athletes. On the other hand, the significant decrease in reduced GSH, Cys, and cysteinylglycine (CysGly) concentrations measured in rugby players at T2 suggested that non-enzymatic antioxidants were strongly consumed during the competitive season, and this finding was closely linked to an overtraining condition. Altogether, the results achieved in the present study confirmed the hypothesis that oxidative stress and antioxidant measurements play a peculiar role in monitoring the athletes’ training response and performance, whose variations are in turn strictly linked to the played activity.