Strength training after sixty

Harvard Health Letter, July, 1993 by Robert Dinsmoor

For years, exercise gurus have been urging seniors to go the distance -- to walk, pedal, or paddle their way to better endurance and a greater aerobic capacity. But now there's evidence that maintaining an independent lifestyle requires strength as well. Although few of us have been conditioned to think of pumping iron as a retirement activity, exercise specialists say there are types of training that can help even very old folks to regain much of the strength that has ebbed with the passing decades. The benefits, they believe, can be enormous.

"Aerobic exercise and strength training are really quite different, and you can't get many of the benefits of one from the other," emphasized Maria A. Fiatarone, an assistant professor in the Division on Aging at Harvard Medical School and a researcher with the USDA Human Nutrition Research Center on Aging at Tufts University, located in Boston. Aerobic activities such as walking and cycling require moving large groups of muscles hundreds or thousands of times against little or no resistance except gravity. Strength training, on the other hand, involves working small groups of muscles only a few times against a high, and gradually increasing, degree of resistance. Aerobic exercise improves cardiovascular fitness and boosts the body's ability to burn oxygen, but it has little effect on strength or muscle mass.

Dr. Fiatarone usually recommends that older people pursue a combination of strength training and aerobic conditioning. If an individual is especially weak, however, he or she should start with strength training and add aerobics later. Contrary to the conventional wisdom, strength training appears safer than most aerobic exercises. "When very frail people want to exercise, many doctors recommend walking because they think it's safe. But people who are weak and have terrible balance are likely to fall. They should get strength training before they start walking," advised Dr. Fiatarone.

Fading power

As almost anyone past middle age can attest, muscle strength increases during early adulthood, levels off around age 30-40, and then decreases in those who don't engage in muscle-strengthening exercise. People who live to age 80 lose an estimated 30-40% of their peak strength before they die.

Muscles become less bulky as the size and number of their constituent fibers decrease. Although a muscle fiber can't be replaced after it is lost, proper exercise can restore at least some shrunken ones to their former robustness.

The claim that exercise can improve dwindling strength and muscle mass is supported by the observation that young people who are bed-ridden lose muscle in much the same way as elderly people do. Experts believe that atrophy is due to disuse as well as age. Although few older people take to their beds, many fall into routines that demand minimal speed or force.

Standing on your own two feet

Strong muscles help to protect against injury. Recent studies indicate that having weak arms and legs makes it harder for older people to walk, climb stairs, dress, rise from a chair, or get in and out of the bathtub, interfering with independent living.

Strength is needed for balance, and researchers rate leg weakness as an important contributor to falls. Studies indicate that one-third of seniors living in the community have fallen during the last year, and nursing home residents lose their footing an average of 1.7 times per year. Falls are responsible for about half of all injuries in seniors, and the likelihood of hip fracture rises for people with weak ankles or quadriceps (large thigh muscles that extend the knees and flex the hips).

Getting it back

Over the past five years a series of studies has indicated that appropriate training can bring about remarkable gains in strength and muscle mass in seniors. At the USDA Human Nutrition Research Center on Aging at Tufts University, for example, 12 men aged 60-72 embarked on a training program using a machine designed to build up the thigh muscles. After workouts three times weekly for 12 weeks, measurements showed that on average the men's extensors (which straighten the knee) were 107% stronger and their flexors (which bend the joint) were 226% mightier than before the program. Muscle mass in their thighs also increased significantly.

Strength training can benefit the upper body as well. Researchers at McMaster University in Hamilton, Ontario, enrolled 14 men aged 60-70 in a 12-week weight-lifting program. Participants used a weight-stack machine to try to increase the strength of one arm only. When the study ended, the lifting ability of the trained arms had increased by an average of 48% while that of the untrained ones remained the same. A University of Wisconsin team has found evidence that elderly women can also regain lost power and muscle mass. A group of 17 women with an average age of 72 embarked on a 50-week regimen combining aerobic activities with strength training. The program included doing wall push-ups, climbing stairs while wearing weighted backpacks, and performing resistance exercises using rubber tubing. Compared with a group of similar women who were sedentary, the active women showed significantly increased aerobic capacity, greater leg strength, and larger fast-twitch muscle fibers (the type needed for bursts of force) in their thighs.