We hypothesized that increased oxidative stress and disrupted redox balance may be predisposing factors and markers for overreaching (OR).
Purpose: The study's purpose was to examine whether oxidative stress markers and antioxidant status and physical fitness are related to OR during an 8-wk military basic training (BT) period.
Methods: Oxidative stress and antioxidant status were evaluated in the beginning and after 4 and 7 wk of training in 35 males (age = 19.7 ± 0.3 yr) at rest and immediately after a 45-min submaximal exercise. Physical activity (PA) was monitored by an accelerometer throughout BT. Indicators of OR were also examined.
Results: From baseline to week 4, increased daytime moderate to vigorous PA led to concomitant decreases in the ratio of oxidized to total glutathione (GSSG/TGSH) and GSSG. After 4 wk of BT, GSSG/TGSH and GSSG returned to the baseline values at rest, whereas PA remained unchanged. At every time point, acute exercise decreased TGSH and increased GSSG and GSSG/TGSH, whereas a decrease was observed in antioxidant capacity after 4 wk of training. In the beginning of BT, OR subjects (11 of the 35 males) had higher GSSG, GSSG/TGSH, and malondialdehyde (a marker of lipid peroxidation) at rest (P < 0.01-0.05) and lower response of GSSG and GSSG/TGSH ratio (P < 0.01) to exercise than non-OR subjects. Moreover, OR subjects had higher PA during BT than non-OR (P < 0.05).
Conclusions: The sustained training load during the last 4 wk of BT led to oxidative stress observable both at rest and after submaximal exercise. Increased oxidative stress may be a marker of insufficient recovery leading possibly to OR.