I nactivity can cause men and women to lose significant amounts of muscle and bone mass by age 55. Left unchecked, this process continues well into later years, leading to frailty. That triggers imbalance, depression and an increased risk for chronic illness, particularly heart disease and diabetes.

At Tufts University, we’ve discovered that strength training can turn back the clock and make our bodies physically and metabolically more youthful. Moreover, initial results take only four weeks.

USE IT OR LOSE IT

The body contains more than 600 muscles. They power every move. Muscles are made up of tiny tissue bundles that are clustered into units. When these units receive nerve impulses, they release chemicals that cause the muscle fibers to contract and relax repeatedly.

The body does not maintain unused muscle. Hence, muscle wastes away. Strength training stimulates muscle cell growth and increases the production of enzymes that help store and use energy. It also reactivates muscle units that have lain dormant because of inactivity.

Example: When NASA sent the first astronauts into space, they returned weakened, with significant drains in muscle and strength reserves. In the weightlessness of space, they weren’t using their muscles. Today, exercise equipment is on every flight.

Muscles are protected by a framework of more than 200 bones, joined by ligaments and connective tissue. Like muscle, bone is constantly undergoing repair and renewal.

Of the major factors that influence bone formation, physical impact is most important.

Example: Walking stimulates bone growth more than swimming.

After age 35, bone mass begins to decrease. The most critical time for preventive measures is age 50 and beyond, when the rate of bone loss increases. This is especially true for women, who don’t have as much of the male hormone testosterone to protect their bone and muscle reserves.

If bone loss isn’t stopped, it often results in osteoporosis. The bones become very fragile and subject to fracture, even from activities like bending over.

Strength training improves bone density because the tug of muscle against bone works the same way other types of physical impact do.

Evidence: A study comparing the racket arm with the other arm of professional tennis players found that the playing arm was 15% to 20% denser.

In our study at Tufts, the strength-training group gained an average 1% of bone density in the hip and spine over one year.

Building bone and muscle also helps improve balance, which experts say starts to deteriorate in middle age.

Balance relies on an important flow of information about the body’s position to the brain. This reflex can’t work well unless the muscles are strong and the joints flexible enough to respond to changes in position.

Our research demonstrated a 14% increase in balance scores among people who had one year of strength training versus an 8% decline in those who didn’t.

STRENGTH-TRAINING BASICS

Strength training can be done anywhere. All it takes to see results is the proper equipment and a commitment to the program for at least four weeks.

To start, you’ll need a pair of dumbbells that are five pounds each for men, three pounds for women. Also, get ankle weights, the type with compartments for 20 pounds of weights. Finally, find a sturdy chair with a seat that is high enough and deep enough so that your knee joint is just over the edge when you sit. You can increase the weights by one or two pounds every other week as you build up your strength.

The basic program requires three 20-minute exercise sessions weekly.

Chair stand (warm-up): Sit toward the front of the chair seat with feet flat on the floor, shoulder-width apart, and arms crossed against the chest. Your fingertips should touch opposite shoulders.

Keeping the back straight, lean forward slightly and stand up slowly. Pause. Slowly return to starting position. Rest and repeat eight times for two sets.

Remember to move slowly and lean forward slightly as you start the move.

Overhead press: Stand straight, arms at your sides with dumbbells in each hand. Your palms should be facing forward, and your feet should be shoulder-width apart. Push dumbbells up until arms are overhead and extended. Make sure that the dumbbells don’t move forward or out as you lift. Pause, and slowly lower to starting position. Repeat eight times for two sets.

Bent-over row: Sit forward in the chair, feet flat on the floor, shoulder-width apart, with a dumbbell in each hand. Allow arms to hang at sides, palms facing inward. Bend slightly forward at the waist, with back straight and abdominal muscles slightly contracted, until your chest is just above your thighs.

Using shoulder and upper-back muscles, pull dumbbells straight up to your rib cage. Make sure your head, neck and back are in a straight line and your back isn’t arched. At the top of the move, your elbows should point back. Pause, and slowly lower dumbbells to starting position. Repeat eight times for two sets.

Important: If you have osteoporosis or back problems, speak to your doctor before doing this exercise.

Calf raise: Stand behind the chair with fingertips resting on the chair back. Slowly raise yourself up on the balls of your feet, hold for three seconds. Lower heels to starting position. Pause, and repeat eight times for two sets.

Knee extension with ankle weights: Sit back in chair with feet shoulder-width apart and a towel rolled up under your knees for padding. Toes should brush the floor. Rest hands on thighs. Slowly raise right leg until the knee is as straight as possible, with toes flexed upward. Pause, and lower leg slowly while relaxing the ankle and toes. Repeat with opposite leg. Repeat eight times with each leg for two sets.

It’s important to cool down by stretching for about five minutes after each session. Finally, remember to go slowly and breathe throughout your training.