Even elderly adults should exercise.

Washington -- As long as they're healthy, adults of any age should be encouraged to exercise, because studies show that it's a safe way to improve their cardiovascular health.

"It turns out that healthy older adults are able to make the necessary cardiovascular adjustments--and physiological homeostasis is preserved--and they are able to exercise effectively," said Douglas Seals, Ph.D., a physiologist who studies aging and exercise at the University of Colorado, Boulder. He spoke at the annual meeting of the Society of Geriatric Cardiology.

The aging process decreases the maximum exercise capacity in healthy adults by approximately 10% per decade of life, but it's important to remember at any age, individuals can exercise to achieve a higher aerobic capacity than their less-active peers, Dr. Seals said.

"Aging will limit the absolute intensity and duration of submaxi-mal aerobic exercise that can be performed by older adults. There's no way around that. However, performance of sustained submaxi-mal exercise is not impaired by advancing age," Dr. Seals said.

"Your patients are performing submaximal exercise when you ask them to exercise, not maximal exercise, so the ability to perform submaximal exercise is important," he continued.

To illustrate how healthy older adults respond to exercise, Dr. Seals cited a study that compared measurements during and after submaximal physical exertion in sedentary and trained groups of both healthy young men (aged 20-32 years) and healdiy older men (aged 60-70 years).

The volunteers walked on a treadmill for 60 minutes with enough effort to reach 70% of their maximum oxygen uptake, or V[0.sub.2] max.

Both groups of older men had smaller increases in heart rate and lower rates of perceived exertion than did the younger men.

Plasma lactate responses, which can be used to indicate metabolic stress in muscles, were also smaller in the older men.

Plasma catecholamine responses, which can show a physiological stress response to exercise, barely increased in any of the men (J. Appl. Physiol. 1988; 65:900-8).

"One could reasonably interpret these data to mean that older adults undergo a smaller increase in physiological stress from the resting state, compared with young adults in submaximal exercise conditions," Dr. Seals remarked.

He and his colleagues reinforced these findings in a similar study of young and elderly men during a 45-minute treadmill walk (Clin. Physiol. 1995;15:169-81).

The older men had lesser increases in heart rate, internal body temperature, and plasma norepinephrine concentrations than did the younger group.

"What we concluded was that older adults demonstrate equivaent, or even reduced, cardiovascular and thermal adjustments, compared with young adults during submaximal exercise. That's good news," Dr. Seals said.

The take-home message for clinicians is that older adults make the necessary cardiovascular adjustments to handle submaximal exercise, he said.

In fact, prolonged exercise at the same relative workload may represent less of a challenge to older adults than to younger ones.

BY HEIDI SPLETE

Senior writer