CoQ10 functions in every cell of the body to synthesize energy. It also has antioxidant properties, protecting your body from damage produced by the byproducts of energy use. But like many important substances naturally produced in the body, the amount in your cells is strained by activities that burn alot of energy like working out. Normal body CoQ10 levels also decline with age so as you grow older, supplementing becomes important even without stressful activities.
At recommended levels doesn't seem to have any side effects. The benefits of CoQ10 are being researched for many different things but the effects have been most confirmed so far for a significantly healthier heart. You will be working your heart hard during exercises. Protect it with the daily recommended amount of CoQ10.