Strenuous physical exercise can augment oxygen consumption by 10-15 fold over resting conditions. •This increased oxidative metabolism leads to an increased production of free radicals.

     An increased formation of free radicals can be particularly observed when the electron flow through the cytochrome chain is high, hypoxia provides an abundance of hydrogen ions to react and leads to a high concentration of transition metals (Fe, Cu, Mg) to catalyze radical formation.

     The resulting oxidative stress may lead to lipid peroxidation and amage of muscle cell membranes. •A defense system of antioxidant scavengers (e.g. vitamins and provitamins) and associated enzymes (e.g. glutathione peroxidase, dismutases, catalases) reduce the oxidative stress.

   Exercise causes an increase in free-radical formation only when it is exhaustive. Changes in indicators of free-radical damage occur only when exercise is exhaustive and are independent of the absolute intensity of exercise.

Few studies demonstrate increased lipid peroxidation and structural damage in highly trained athletes.   If the athletes feeds on a well balanced diet there is no evidence that they need to be supplemented with additional antioxidants (e.g. Vitamin E, Vitamin C, beta-caroten).

       The recreational sportsperson, who does not train regularly may not have this improved antioxidant capacity and is probably more susceptible to oxidative stress.

The benefits from supplementation with antioxidants in terms of preventing lipid peroxidation and muscular damage have not been clearly demonstrated and much further work on the relevant pathogenic mechanisms of stress metabolism is still required.

    Supplementation with dietary antioxidants partially prevents muscle damage caused by exhaustive exercise. However, in many cases the supplements or media used (liquids) have strong oxidative properties itself ! It is recommended to use pure water as a suplementation media or for the best effectivenes use water with negative ORP (redox potential).