Some experts suggest that lifting weights is the best way to keep our bodies strong and healthy as we age. Weight lifting is a type of resistance training. Penn State University College of Medicine experts define resistance training as a type of exercise that causes your muscles to work against an outside resistance. Some experts claim resistance training can even slow aging. Marcas Bamman has researched the effects of weight-resistance training on aging bodies for many years. He shared his advice recently with the Associated Press. “Resistance training is in many ways the true fountain of youth,” Bamman said. Our bodies do have biological limits. But Bamman said older people put too few demands on their bodies, not too many. He said that most age-related loss of strength, flexibility, and endurance comes from the lack of physical demands on our bodies, such as exercise.