A dietary supplement used by athletes and bodybuilders can increase the fitness of senior men and women, according to a new study.

Researchers at the University of Oklahoma said that beta-alanine, known as BA, improves muscle endurance in the elderly.

"This could have importance in the prevention of falls and the maintenance of health and independent living in elderly men and women," said Dr. Jeffrey Stout.

BA is an amino acid that, together with histidine, forms the dipeptide carnosine. Carnosine is found in muscle tissue and makes an important contribution to the maintenance of the acidity in cells, which is vital for normal muscle function during intense exercise, a news release on the work said.

In the experiment, which was randomized and included a control group, 26 elderly men and women were given either a 90-day course of BA supplementation or placebo pills. Their fitness levels were tested before and after the course.

Sixty-seven percent of the people who took BA showed an improvement in their fitness levels, compared to 21.5 percent of the people receiving the placebo treatment.

"Our data suggest that 90 days of BA supplementation increases physical working capacity in elderly men and women. These findings are clinically significant, as a decrease in functional capacity to perform daily living tasks has been associated with an increase in mortality, primarily due to increased risk of falls," the report says.

The research appears in BioMed Central's open access Journal of the International Society of Sports Nutrition.