Does exercise teach your body to stay young?

It certainly looks that way. Researchers in Tel Aviv studied rats who exercised daily for three months and found that "younger rats showed a 20% to 35% increase in the average number of stem cells per muscle fiber retained -- and older rats benefited even more significantly, exhibiting a 33% to 47% increase in stem cells.

The greater prevalence of stem cells among those who exercise enhances the ability to rejuvenate tissue and avoid two of the major symptoms of aging: sarcopenia, a decline in mass and function of muscles, and osteopenia or bone loss.