We hypothesized that increased oxidative stress and disrupted redox balance may be predisposing factors and markers for overreaching (OR).
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.
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.
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).
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.
1Department of Biology of Physical Activity, University of Jyväskylä, FINLAND; 2Department of Clinical Physiology and Nuclear Medicine, Helsinki University Hospital, Helsinki, FINLAND; 3Polar Electro Oy, Kempele, FINLAND; and 4Institute of Biomedicine/Physiology, University of Eastern Finland, Kuopio, FINLAND
Address for correspondence: Minna M. Tanskanen, M.Sc., Department of Biology of Physical Activity, University of Jyväskylä, Kidekuja 2, Snowpolis, 88610 Vuokatti, Finland; E-mail: email@example.com.
Submitted for publication September 2010.
Accepted for publication January 2011.