This study sort of makes an assumption that increased free radicals causes (at least in part) aging (free radical theory of aging). The relationship between rad

This study sort of makes an assumption that increased free radicals causes (at least in part) aging (free radical theory of aging). The relationship between radical oxygen species (free radicals) and aging is not at all clear to my understanding. (this paper is from 1997) Moreover, it's possible that the tissues most susceptible to oxidative stress during exercise (i.e. muscle) are also most adapted to handle it. So overall, yes ROS increase but mostly just in muscle where it is well-adapted to handle it, and the benefits of exercise (lowering blood pressure, better circulation, etc) trump any detriments of increased ROS. Edit: Found this review [ http://www.ncbi.nlm.nih.gov/pubmed/23434764 http://www.ncbi.nlm.nih.gov/pubmed/23434764 ] that considers evidence that ROS may actually be a part of a pro-survival signal cascade