A recent study in the PLoS scientific journal showed that engaging in weight training regularly can offset skeletal muscle atrophy and functional impairment associated with aging. Seniors who participated in six months of gentle exercises had almost as much energy and strength as people less than half their age. The study involved training twice a week for an hour with participants utilizing basic gym equipment and engaging in commonly offered exercise sessions. After six months the researchers harvested tissue samples from the thigh and found that these muscles were stronger but that some of the cellular features associated with aging were seemingly reversed. Researchers looked at the energy generating structures within the cell, the mitochondria. As we age, mitochondria generally become less active. However, in this study, researchers discovered that these structures generated almost as much energy as ones found in people age 20 or 30 years. Researchers now intend to examine whether running, swimming or other stamina building exercises can have the same effect on cellular mitochondria. As the population continues to age, information is building about scientifically valid methods of slowing or reversing cellular aspects of the aging process. The good news is that the greatest benefits for most people come from just moderate levels of exercise, compared to leading a sedentary life. Extreme exercise and physical activity are not needed for good health, and may even become counterproductive.