Free radicals are a byproduct of normal cell function. When cells create energy, they also produce unstable oxygen molecules. These molecules, called free radicals, have a free electron. This electron makes the molecule highly unstable. The free radical bonds to other molecules in the body - causing proteins and other essential molecules to not function as they should.
Weight Training, Exercise and Antioxidants In sports medicine studies, it's been shown that vigorous exercise produces free radicals because energy systems and metabolism are ramped up during exercise, eating to fuel exercise, and even after exercise to some degree. Antioxidant supplements were once considered useful to stem the possible damage that exercise-induced free radicals might do to muscle and other tissues -- perhaps even to prevent sore muscles in the days following exercise. In addition, benefits to immunity and general dietary compliance have been postulated.
However, other studies showed that the body adapted to the onslaught of exercise-related free radicals by increasing the body's internal, natural antioxidant defense systems -- certain enzymes -- perhaps even to a level greater than in non-exercisers. In other words, the body was adjusting to the oxidative stress of exercise and probably needed no assistance from anti-oxidants. And this adaptive response might even be a cornerstone of the health effects of exercise.