FRIDAY, Aug. 1 (HealthDay News) -- Taking creatine doesn't improve exercise outcomes in people who have chronic obstructive pulmonary disease (COPD), a U.K. study reports.

Creatine is a popular nutritional supplement used to enhance athletic performance and muscle strength. This study included 100 COPD patients who received either creatine or a placebo during a seven-week pulmonary rehabilitation program.

Of the 80 patients who completed the study, there were no differences in muscle strength between those who took creatine and those who got the placebo. Any benefits of creatine may have been overshadowed by the effects of physical training, the researchers suggested.

"We have evidence to suggest Cr [creatine] uptake into muscles (in COPD patients), but are unable to explain why an increase in muscle Cr did not enhance training," wrote study lead author Dr. Sarah Deacon, specialist registrar at the Institute for Lung Health at Glenfield Hospital in Leicester, England.

The study was published in the first August issue of the American Journal of Respiratory and Critical Care Medicine.

The findings suggest there's no substitute for the hard physical work that's an essential component of pulmonary rehabilitation.

"Those of us interested in pulmonary rehabilitation are happy to see confirmation of the beneficial effects of exercise training. This information indicates that creatine supplementation not be viewed as a substitute for exercise training," wrote Dr. Francoise Maltais and colleagues at the Centre de Recherche de l'Hospital Laval in Quebec, Canada.

More information

The American Academy of Family Physicians has more about COPD.