Almost everyone should lift weights. Weight lifting strengthens bones, muscles ligaments and tendons; increases coordination for tasks requiring strength; and gives confidence and mobility to elderly or disabled people.

Just exercising doesn't do much to strengthen muscles. If it did, marathon runners would have the largest muscles. To become strong, you have to exercise your muscles against progressively greater resistance.

Just exercising doesn't strengthen bones either. Female marathon runners sometimes stop menstruating and lose tremendous amounts of bone, even though they may run more than 100 miles a week. To regain bone, they have to eat more food which will usually start them menstruating again, and include weight-lifting in their workouts. They may also need to take estrogen.

Many people with muscle or nerve diseases can also benefit from lifting weights. They may be unable to work out as long or as hard as a healthy person and they will take longer to recover from their workouts. However, if they stop exercising when their muscles feel heavy or hurt and they take off when their muscles feel sore, they can make dramatic increases in strength.

Anyone starting a weight training program should be guided by an experienced instructor. Exercise with several different machines two or three times a week, never on consecutive days. On each exercise, use the heaviest weight you can lift comfortably eight or ten times in a row without losing your form. Do three sets of ten repetitions on each machine. Then allow at least 48 hours for your muscles to recover. Do not lift again until the soreness is gone.