Recent research has revealed that intake of some vitamins nullify beneficial effects produced by the excercise. Research team led by Dr Michael Ristow, from the University of Jena in Germany found that intake of vitamins C and E after the exercise can neutralise destructive free-radical molecules.

These "free radical" molecules known as reactive oxygen species (ROS) are by-product of metabolism and generated in larger numbers during vigorous exercise.

Research has shown that these free radicals increase body's sensitivity to insulin. Antioxidant vitamins destroy these molecules which in return destroys the beneficial effect.

Dr Michael Ristow said: `We propose that transiently increased levels of oxidative stress reflect a potentially health-promoting process, at least in regards to prevention of insulin resistance and type 2 diabetes mellitus.'