Oxidative Stress in Collegiate Cross Country Skiers in Mid- and Post-Seasons

The oxidative stress (OS) hypothesis of overtraining syndrome argues that increased production of free radicals through exercise cause muscle fatigue and damage resulting in lower athletic performance. Several studies have investigated OS immediately before and after exercise bouts in a training macrocycle. Our study aimed to compare OS of endurance athletes between a competition macrocycle and the immediate post-season recovery macrocycle. In addition, we aimed to identify athletes who experienced an unexplainable drop in athletic performance during the competition season in order to compare their OS to those who experienced no drop in performance.

Fifteen members of the University of Alaska Fairbanks cross country ski team volunteered for this study. Blood samples were taken in early February ("mid-season") and late April ("post-season"). Participants completed questionnaires regarding physical activity and athletic performance at the time of the blood draws. Plasma was analyzed for 4-hydroxynonenal (HNE), nitrotyrosine, nitric oxide (NOX), and superoxide dismutase (SOD). Significance was determined by Wilcoxon and Mann-Whitney tests.

Participants displayed significantly higher (p < 0.05) SOD activity in the post-season (0.02065 U/mL ± 0.006477 SEM) as compared to mid-season (0.04459 U/mL ± 0.005860). Six athletes reported an unexplainable drop in performance (6D). In the post-season, HNE concentration was significantly higher (p < 0.05) for 6D (197.5 μg/mL ± 22.79) than for participants who did not report such a drop (69.80 μg/mL ± 33.59). 6D SOD activity was significantly higher in post-season (0.05048 U/mL ± 0.004688) than mid-season (0.01241 U/mL ± 0.006469).

Signs of oxidative stress and mitigation during the post-season recovery macrocycle were higher in athletes who reported experiencing a drop in athletic performance during the competition season macrocycle.