Another benefit of exercise: "exercise increased the number of satellite cells (muscle stem cells) - a number which normally declines with aging. The researchers believe that a decline in the number of these cells and their functionality may prevent proper maintenance of muscle mass and its ability to repair itself, leading to muscle deterioration. Comparing the performance of rats of different ages and sexes, they found that the number of satellite cells increased after rats ran on a treadmill for 20 minutes a day for a 13-week period. The 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. ... Endurance exercise also improved the levels of 'spontaneous locomotion' - the feeling that tells our bodies to just get up and dance - of old rats. Aging is typically associated with a reduced level of spontaneous locomotion. The combination of aging and a sedentary lifestyle significantly contributes to the development of diseases such as osteoporosis, obesity, diabetes and cardiovascular diseases, as well as a decline in cognitive abilities. If researchers can discover a method to 'boost' satellite cells in our muscles, that could simulate the performance of young and healthy muscles - and hold our aging bones in place."