A noted geriatric psychiatrist once said that if exercise was a pill, it would be the most prescribed medication in the world.

Seniors are popping the fitness pill like never before. The Sporting Goods Manufacturers Association reports that seniors are exercising more than any other age group. Aquatic exercise, fitness walking, golf, stationary cycling, and cross-country skiing are the most popular activities for people age 55 and above.

Still, only one in four seniors exercises regularly. The USDA Human Nutrition Research Center at Tufts University recognizes seven “biomarkers of aging,” factors that directly affect aging: muscle mass and strength, metabolic rate and body fat percentage, aerobic capacity and blood sugar tolerance, cholesterol and HDL and LDL balance, blood pressure, bone density, and temperature regulation.

Each condition can be improved by regular physical activity.

Research at the University of Texas Medical Branch in Galveston shows that inactivity can hasten aging and muscle wasting and reduce endurance, flexibility and balance.

Regular activity, though, can prevent or minimize the onset of chronic conditions. To help stave off the risk of osteoporosis and bone fracture, for example, post-menopausal women–who are at increased risk for bone fractures–are urged to take up weight bearing exercise like walking. Such movement can help maintain mineral content in leg and hip bones.

Fewer falls and cracked bones means staying mobile, says gerontologist Bridget Thompson of Mission Bay Hospital Senior Health Center in San Diego. “Part of the aging process is you lose a lot of muscle tone,” says Thompson. “In doing that it decreases your mobility and that affects your ability to be able to live independently.

Mission Bay Hospital is typical of the increased recognition of exercise among medical centers and health groups as a key component of recovery from illness and disease prevention among seniors. Says Thompson, “What older adults value in their life is their independence. Exercise is the key to maintaining that independence, to be able to keep that as long as possible in life.”

The American Medical Association reports that physically active older adults were 40 percent less likely to show loss of mobility over a 4 year time span. One study showed that women who spent less than 4 hours a day on their feet had nearly twice the risk of hip fractures as their more active counterparts.

Those already suffering many diseases can benefit from the therapeutic value of exercise, with the approval of doctors. In revised thinking among cardiologists, based on research from institutions like Duke University Medical Center, coronary artery disease patients can reduce their risk of death from a cardiac event by 20 to 25 percent with exercise. Risk factors for heart attacks, including hypertension, obesity, high cholesterol, and diabetes, can be reduced even further.

Kendall Webb and his wife Dixie Madsen are seniors who are changing the face of fitness. Their whole-hearted commitment to fitness benefits their physiques as well as their outlooks. A star athlete since high school, Webb is a devoted weight trainer and has the buff body to prove it. (An ID check verifies his assertion that he’s approaching seventy.) “I just don’t think about aging,” says Webb. To me, the elderly are always people 20 to 30 years older than we are. This is a lifetime interest and it will hopefully extend our life.”

Like her husband, Madsen, age 63, participates in body building competitions. She also runs marathons. “I feel better now definitely than in my thirties,” says Madsen, who shares strength training with her spouse. “I see the benefit of being able to go into old age without the ailments [of] our parents.”

The couple’s mutual passion for exercise exemplifies the value of a combining camaraderie and fitness. Webb’s wife motivates him when he’s a little slow to don his running shoes: “When I just don’t quite feel like it I think, ‘If she’s going to do it, I can do it too,’” he says.

“Choose something that you enjoy and be involved in it regularly with a partner,” says Thompson, who organizes group fitness, social gatherings, and field trips at Mission Bay Hospital through a branch of Senior Friends. “A friend or group will keep you going. Maintain three to four times a week, 20 to 30 minutes, and get an exercise program that you’ll stick to. Walking, gardening, biking, water aerobics, yoga, tai chi, stretching: any way you’re utilizing muscles and bones.”

Exercise benefits people of any age or starting point. It’s never too late, studies show. The effect of exercise on mortality was studied among 8,000 British men, long-time devotees to a sedentary lifestyle, males between the ages of 52 and 72. Subjects were interviewed and evaluated a decade after beginning to exercise, even light exercise. In the four years following the interview, exercisers were 45 percent less likely to die of any cause than non-exercisers. Working out vigorously was no more helpful than moderate activity like walking, the study found.

“Anything is better than nothing!” notes Thompson.