Free radicals in exercise

Reactive oxygen species (ROS) are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. ROS form as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis. However, during times of environmental stress (e.g., UV or heat exposure), ROS levels can increase dramatically. This may result in significant damage to cell structures. Cumulatively, this is known as oxidative stress. ROS are also generated by exogenous sources such asionizing radiation.

Apart from their harmful effects on the cell (damage of DNA, oxidations of polyunsaturated fatty acids in lipids, oxidations of amino acids in proteins, and oxidatively inactivate specific enzymes by oxidation of co-factors) they can greatly affect training and racing performance.

There are two articles written by Li Li Ji that were published at the Journal of Exercise Science and Fitness (here) and the Experimental Biology and Medicine (here) that will help you understand ROS and how they affect your body and what to do to diminish these effects.