Electron spin resonance spectroscopy, exercise, and oxidative stress: an ascorbic acid intervention study.

Oxygen free radicals are highly reactive species that are produced in increased quantities during strenuous exercise and can damage critical biological targets such as membrane phospholipids. The present study examined the effect of acute ascorbic acid supplementation on exercise-induced free radical production in healthy subjects. Results demonstrate increases in the intensity of the alpha-phenyl-tert-butylnitrone adduct (0.05 +/- 0.02 preexercise vs. 0.19 +/- 0.03 postexercise, P = 0.002, arbitrary units) together with increased lipid hydroperoxides (1.14 +/- 0.06 micromol/l preexercise vs. 1.62 +/- 0.19 micromol/l postexercise, P = 0.005) and malondialdehyde (0.70 +/- 0.04 micromol/l preexercise vs. 0.80 +/- 0.04 micromol/l postexercise, P = 0.0152) in the control phase. After supplementation with ascorbic acid, there was no significant increase in the electron spin resonance signal intensity (0.02 +/- 0. 01 preexercise vs. 0.04 +/- 0.02 postexercise, arbitrary units), lipid hydroperoxides (1.12 +/- 0.21 micromol/l preexercise vs. 1.12 +/- 0.08 micromol/l postexercise), or malondialdehyde (0.63 +/- 0.07 micromol/l preexercise vs. 0.68 +/- 0.05 micromol/l postexercise). The results indicate that acute ascorbic acid supplementation prevented exercise-induced oxidative stress in these subjects.