Exercise-induced oxidative stress and muscle performance in healthy women:role of vitamin E supplementation and endogenous oestradiol

The purpose of this study was to investigate the individual and combined an tioxidant effects of menstrual cycle phase-related alterations in blood ser um oestradiol concentrations and of dietary vitamin E supplementation on ex ercise-induced oxidative stress and muscle performance. A group of 18 seden tary women, aged 19-35 years, were given supplements of 300 mg alpha -tocop herol (n = 10) or placebo (n = 8) daily during the course of two menstrual cycles. The subjects exercised the knee isokinetically to exhaustion after cycling submaximally at 50% maximal oxygen uptake during the menstrual and preovulatory phases of their menstrual cycles. Blood samples were taken bef ore and after the exercise, to evaluate haematocrit, plasma lactic acid and malondialdehyde concentrations, erythrocyte antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and apolipopro tein B containing lipoprotein (non-high density lipoprotein, HDL, fraction) oxidation. Serum vitamin E, follicle stimulating hormone, luteinizing horm one and oestradiol concentrations were measured in pre-exercise blood sampl es. Neither vitamin E supplementation nor oestradiol concentrations influen ced SOD and GPx activities or the susceptibility of the non-HDL fraction to oxidation while at rest. Plasma malondialdehyde concentration was unaffect ed by exercise, however significant reductions in erythrocyte SOD and GPx a ctivities and increased susceptibility of the non-HDL fraction to oxidation were noted after exercise. Exercise-induced changes were reduced when oest radiol concentration was high in the preovulatory phase, independent of the serum vitamin E concentrations. In addition, both pre-(r = 0.58, P < 0.05) and post-exercise (r = 0.73, P < 0.001) GPx activities in placebo administ ered subjects were positively correlated with oestradiol concentrations. In conclusion, these findings suggest a better protective role of oestradiol against oxidative injury, compared to vitamin E. Exhausting muscle performa nce was, however, not influenced by vitamin E supplementation and/or cycle- phase related changes in oestradiol concentrations.