Strength training can slow and even reverse the declines in
strength, bone density and muscle mass that accompany aging. The
American College of Sports Medicine recommends weight training
for people over 50 in addition to aerobic activity and
stretching. "Generally, sedentary people can lose up to 10
percent of their lean muscle mass each decade after age 30,"
says Edward Laskowski, M.D., a physical medicine and
rehabilitation specialist and co-director of the Sports Medicine
Center at Mayo Clinic, Rochester, Minn. "If you don't do
anything to replace that loss, you're losing muscle and
increasing fat," says Dr. Laskowski. "But if you do weight
training, you can preserve and enhance your muscle mass. It's
like having a V-8 engine instead of a 4-cylinder. You have a
bigger engine to burn more calories because it takes calories to
keep that engine running." Aerobic exercises like running,
walking and bicycling strengthen the heart by forcing it to
adapt to the stress in a positive way. Similarly, weight trainin