Exercise increases the generation of oxygen free radicals and lipid peroxidation. The aim of this study was to investigate the oxidant and antioxidant status in sedentary middle-aged (36.8 +/- 5.4 years, n = 20) and postmenopausal women (51.4 +/- 3.3 years, n = 11) before and after acute calisthenic exercise. Both subject groups performed an acute calisthenic exercise for 55 minutes. The intensity of the exercise was 60-70% of maximal heart rate, as determined by Karvonen et al. Plasma malondialdehyde (MDA), gluathione (GSH), ascorbic acid (AA) and nitric oxide (NOx) levels were determined spectrophotometrically.