JULY 2008

A brisk walk may not exactly lead you to the fountain of youth—but a new research review suggests it’s a good start. According to the report in the British Journal of Sports Medicine, vigorous walking for about an hour a day, five times a week, can boost your maximal oxygen intake by as much as 25% within just three months. That’s enough to turn back the clock on 12 years of natural decline with aging. For seniors, it could also add a dozen years of functional independence.

Roy Shephard, MD, PhD, of the University of Toronto reviewed 30 studies of subjects age 64 and older published since 1990. He focused on research showing the relationship between aerobic activity, aging and maximal oxygen intake, known as VO2max.

One of the oldest measures of fitness and human performance, VO2max gauges the body’s ability to consume oxygen when you’re exercising your hardest. It depends on the blood-pumping power of your heart, the ability of your blood to carry oxygen, your muscle level and the ability of your muscles to use oxygen. The higher your VO2max—as expressed in milliliters of oxygen per kilogram of body weight per minute (ml/[kg.min])—the better your body can perform over extended periods of activity. Marathon runners have been measured at VO2max values of 80 ml/[kg.min] and above; the average 40-year-old man with no endurance training might score 35-40 ml/[kg.min], with women averaging about 5 points lower.

With age, according to Dr. Shephard, the body tends to lose about 5 ml/[kg.min] in VO2max per decade. As VO2max drops over the years, the amount of activity you can do without getting fatigued declines, too. Once VO2max drops below 18 ml/[kg.min] for men and 15 for women, a person is likely to lose functional independence.

But Dr. Shephard found that aerobic activity such as vigorous walking can not only slow but reverse that decline. And the longer you keep at it, the greater the gains in turning back the hands of time—at least in terms of your body’s oxygen capacity. In an 8-10-week training program, the review found an average VO2max improvement of 12.9%; over 12-18 weeks, the gain averaged 14.1%; with 24-52 weeks of training, VO2max improved an average of 16.9%.

Working harder also pays dividends. The studies that tested a high-intensity regimen recorded VO2max boosts of 25%, an increase of 6 ml/[kg.min]. Since 10 years’ aging naturally takes a toll of about 5 ml/[kg.min], that represents the equivalent of gaining back 12 years of youthful vigor.

In looking at the link between VO2max and functional independence, Dr. Shephard speculated that aerobic fitness may indirectly extend independence by combating other conditions that can take a toll on a person’s ability to live unassisted. These include obesity, diabetes, heart disease, stroke, osteoporosis and even some forms of cancer. Exercise can also build muscle power to help prevent debilitating falls, as well as speeding recovery from injuries.

“There seems good evidence that the conservation of maximal oxygen intake increases the likelihood that the healthy elderly person will retain functional independence,” Dr. Shephard concluded.

He might have added: What are you waiting for? The clock is ticking, but vigorous activity can determine how fast—and even in which direction—the hands of time move for your body.

TO LEARN MORE: British Journal of Sports Medicine, online before print; abstract at dx.doi.org/10.1136/bjsm.2007.044800. Physical Activity for Everyone, www.cdc.gov/nccdphp/dnpa/physical/everyone. National Institute on Aging: Getting Fit for Life www.nia.nih.gov/HealthInformation/Publications/exercise.htm.