Aerobic Capacity Declines Dramatically in Older Years

Aerobics Capacity

Fitness levels decline dramatically as we grow older, but exercise is the key to remaining independent in the golden years, according to a report in Circulation: Journal of the American Heart Association.

"Aerobic capacity declines dramatically with age, making it even more important for people to stay physically active if they want to remain independent," said lead author Jerome L. Fleg, M.D., a cardiologist and medical officer in the division of epidemiology and clinical applications at the National Heart, Lung, and Blood Institute in Bethesda, Md.

Researchers investigated changes in aerobic capacity in healthy people across a broad age group. They analyzed data on 375 women and 435 men, ages 21 to 87, participating in the Baltimore Longitudinal Study of Aging. Participants underwent maximal treadmill exercise testing about every four years for a median 7.9 years, offering researchers a long-term perspective.

Participants' aerobic capacity, the amount of oxygen the body consumes during exercise, which is known as VO2, was calculated during treadmill tests.

As aerobic capacity diminishes, a person commonly does less physical activity, walks slower and more easily becomes exhausted with physical exertion.

"This translates into frailty and difficulty with independent living," Fleg said. "For example, if you have to use 75 percent or more of your aerobic capacity just to make the beds or climb the stairs, you will be quite fatigued trying to do these activities on a regular basis."

Using the treadmill results, researchers calculated the change in aerobic capacity for each decade of age. Aerobic capacity declined in each decade in men and women, but at a far greater rate in older age groups. The rate of decline was 3 percent to 6 percent per decade in the 20s and 30s but more than 20 percent per decade in people in their 70s and beyond.

Beginning in the 40s, men's decline in aerobic capacity was greater than women's, regardless of their reported physical activity. For example, men lost an average of 8.3 percent of exercise capacity per decade in their 40s, and 23.2 percent per decade in their 70s.

"We were surprised at the magnitude of the change in older adults," Fleg said. "Even when we adjusted for differences in body composition (such as muscle mass), the changes were almost as great.

"These results are even more striking given that we were looking at the best-case scenario. Participants were required to have no previous heart attack or stroke and to be healthy and agile enough to walk on the treadmill. The rate of decline in the population-at-large is probably somewhat greater than what we observed here, because many older people will have disease-related deficits in addition to those brought on by age."

To counter age-related declines, Fleg recommends that people maximize their aerobic capacity through exercise.

"This study does not mean that older people can't improve their fitness," he said. "By participating in a training program, you can raise your aerobic capacity 15 percent to 25 percent, which in our study would be equivalent to being 10-20 years younger. Over time, your aerobic capacity will decline, but at any given age someone who exercises will have a higher capacity than someone who is a couch potato."

Declining muscle strength, another factor that contributes to frailty as people age, can also be countered through strengthening exercises, he said.

"These findings emphasize the importance of finding ways to increase the aerobic capacity and strength of older adults. We know that supervised exercise training can bring major improvements, but we need to determine what kind of community programs can get older people up and moving and give the most bang for the buck in terms of results," Fleg said.

The intramural research program of the National Institute on Aging funded the study.

Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.

Editor's note: The American Heart Association's Choose To Move is a FREE 12-week program to help women increase physical activity and build healthy habits to lower their risk for heart disease and stroke. It's part of the American Heart Association's Go Red For Women movement to raise awareness that cardiovascular disease is the No. 1 killer of women and to help women take steps to prevent heart disease and stroke. To register for the program, call 1-888-MY-HEART or visit http://www.americanheart.org/ - DALLAS, July 26