2 articles on how exercise combats the effects of aging

From WebMD on how exercise affects telomere lengths:  http://www.webmd.com/fitness-exercise/news/20091201/molecular-proof-exercise-keeps-you-young

From the NY Times on how exercise improves mitochondria:  http://well.blogs.nytimes.com/2011/03/02/can-exercise-keep-you-young/?_php=true&_type=blogs&_r=0