It's no secret that exercising can help you age gracefully by keeping you fit. But it turns out that endurance exercise, like running, doesn't just tone muscles, it enhances muscle stem cells, too. In a study published  online this month in PLoS ONE , researchers found that the number of muscle stem cells, called satellite cells increased after rats spent 13 weeks running on a treadmill for 20 minutes a day. (The blue dots shown on the muscle fibers in the image inset are muscle cells; the red dots represent satellite cells.) Younger rats showed a 20% to 35% increase in the mean number of stem cells per muscle fiber, while older rats showed a 33% to 47% increase. Since these cells regenerate muscles after injury or illness, the authors believe that the difference in stem cell numbers could explain why human exercisers have better muscle function than nonexercisers as they age. Better muscle quality could also delay sarcopenia, the decline in muscle mass that occurs with aging. Better hit the gym!
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