Introduction: Setting optimal training volume is important to prevent injuries and disorders induced by overtraining when adolescent athletes engage in sport-club activities. On this point, if non-invasive biomarkers related to oxidative stress could be used to monitor the physical condition of athletes, it is expected to provide athletes with some feedback to maintain and improve performance levels for the athletes. The aim of this study was to examine the cumulative effects of 12 months of volleyball training on whole body DNA oxidation (accounted for by urinary 8-hydroxy-2’-deoxyguanosine) in adolescent female athletes.
Methods: Nine eumenorrhoeic female volleyball players (as baseline values; age: 15.2±0.4 year, height: 159.9±5.9 cm, body weight: 54.9±6.4 kg, BMI: 21.4±1.6 kg/m2, body fat: 22.1±4.7 % [mean±SD]) served as the participants. Each athlete performed volleyball training in the school gym, which consisted of ball handling, specialized drills, and practical game-style exercises, including physical training. The training cycle consisted of six days per week, with a total of approximately 2 to 2.5 of volleyball training per day. In order to examine the cumulative effects of whole body DNA oxidation, urine samples were collected before and after volleyball club activities on three successive days (Days 1, 3, and 5) at 0 (baseline) and 12 months (two consecutive summer seasons), respectively, for the later analysis of 8-hydroxy-2’- deoxyguanosine (8-OHdG) determined with high performance liquid chromatography.
Results: A two-way analysis of variances represented main effects for session (p<0.05, 0 and 12 months), but not for day (Days 1, 3 and 5) or interaction regarding the levels of urinary 8-OHdG (ng/ml creatinine, values computed as the average of three successive days, Day 1: 2.1±0.8, day 3: 2.8±0.9, Day 5: 3.1±1.1 for 0 month, Day 1: 4.1±1.4, day 3: 3.8±1.7, Day 5: 3.6±1.3 for 12 months, respectively).
Discussion: Previous studies have found that high-intensity exercise training increases oxidative stress. On the other hand, moderate-intensity exercise training has been reported to increase antioxidant capacity as a result of training adaptation. In this study, increased whole-body DNA oxidation was observed, but it remains to be elucidated whether it is derived from the amount of training (dependent on intensity and duration), induced from hydration status in a warm-humid environment, or derived from hormonal fluctuation (e.g., estrogen). In conclusion, the results of this study suggest the possibility of increased responses in whole-body DNA oxidation to the long-term volleyball training in adolescent female athletes, which appears to be a transient increase.
Impact and application to the field: When adolescent athletes train for extended periods of time in a warm-humid indoor environment such as a gymnasium without air conditioning, measuring biomarkers of oxidative stress can provide useful information for athletes to manage their physical condition.
We have no conflict of interest of relevance to the submission of this abstract.