Free radicals are highly reactive chemicals produced naturally during metabolism. In the body, they bind easily with other chemicals, which can destroy vital structures such as cell membranes and DNA. Free radicals are like biological rust that destroys tissues, contributes to
aging and breaks down the immune system. Some scientists have linked free radical destruction to post-exercise muscle soreness and tissue injury.
Free radical generation is particularly elevated during high-intensity exercise because metabolic rate increases to such high levels. Sprinting and squatting are highly stressful exercises that may potentially generate large quantities of free radicals. University of Memphis researchers determined that trained men experience little oxidative stress when sprinting or squatting. More importantly, they experience less stress than untrained men, so training provides protection against free radical damage during exercise, The practical message from this study is to train all year so you maintain protection against these damaging chemicals. Even if you need a break from training, working out every couple of weeks will maintain some tissue resistance to free radicals.