Exercising one leg at a time can improve aerobic capacity more than two-legged exercise in patients who have stable chronic obstructive pulmonary disease (COPD), according to a report in the latest issue of the medical journal Chest.
"We may have a new approach to enable patients with severe lung disease to improve their fitness," said Dr Roger S. Goldstein. "Hopefully this also increases their mobility, activities, and quality of life."
COPD is a common, progressive lung condition that is mostly seen in smokers and former smokers. It is characterised by emphysema and chronic bronchitis, which obstructs air flow to the lungs. COPD is the fourth leading cause of death in the United States.
Goldstein, from the University of Toronto, Ontario, and Thomas E. Dolmage note that shortness of breath limits exercise intensity for most COPD patients. "One-legged exercise," at half the work load of exercise using two legs, "places the same metabolic demands on the targeted muscles." However the stress on the lungs is reduced, permitting patients to increase their exercise capacity, the researchers point out.
How the study was done
They investigated the effects of one-legged training on the peak oxygen uptake on 18 COPD patients during stationary bicycle exercise compared with conventional two-legged training.
"Two-legged trainers cycled continuously for 30 minutes, whereas one-legged trainers switched legs after 15 minutes." The conditions were otherwise the same in terms of training frequency and session duration.
Both groups were able to increase their training intensity over the duration of the training program, the investigators report, and both groups significantly increased their total work per session.
The researchers found that the improvement in peak oxygen uptake was significantly higher in the one-legged training group than in the two-legged group. The one-legged group also had a significantly greater increase in peak ventilation and lower submaximal heart rate than the two-legged group.
'Easy, inexpensive and effective'
"Although the one-legged group exercised at a higher muscle-specific intensity," the investigators write in their report, "their overall exercise intensity remained below that of the two-legged group."
"This approach enables patients who would otherwise be too short of breath to exercise to train at a lower work load (one that would allow them to continue exercising for longer) by using one leg at a time - in other words, by using a lower muscle mass," Goldstein explained.
The technique is "easy to do, inexpensive, and it's simple to modify a stationary bike," Goldstein pointed out. The best candidates for this program are patients with severe but stable lung disease who would otherwise be too short of breath after minimal exertion to participate in any meaningful exercise.
"Single-leg exercise has been used to study physiologic mechanisms for more than 30 years," writes Dr M. Jeffery Mador, from the University of New York at Buffalo, in a related editorial. "The authors are to be commended for translating this type of study into exercise that is potentially adaptable to clinical practice and may benefit patients with COPD."
More tests planned
Whether this approach is "ready for prime time" or just represents an interesting study will require additional trials with a larger number of patients, along with evaluation of actual patient benefits, the editorialist concludes.
Goldstein said that his group does plan to test the method in a larger sample of subjects before recommending it as an exercise training program for COPD patients. – (Reuters Health) - February 2008