As America ages, a growing public health concern is a condition known as sarcopenia, the loss of muscle strength and function.

Although sarcopenia is a natural part of the aging process, it increases the risk of falls and injuries, and researchers are searching for ways to slow or reverse its progression.

Rick Sharp, a professor of kinesiology at Iowa State University, is testing the effectiveness of a combination of supplements and resistance training in older adults who have been diagnosed with low levels of vitamin D.

He hopes that his study will confirm the results of earlier studies which found that a supplement called HMB (-hydroxy-b-methylbutyrate) will reduce muscle loss.

HMB is a natural body-building compound discovered by scientists at Iowa State.

Earlier research showed that older people who had low vitamin D levels didn't respond as well to HBM as those who had adequate levels.

Sharp's goal is to discover if supplemental vitamin D will improve response to HMB and increase muscle mass and strength.

"We know that sarcopenia is so predictable in older adults that anything we can do that slows down the progression and/or reverses it, is going to be effective," Sharp said.

"If all we were to do is prevent their muscle mass and function from dropping, we've already had a real positive impact.

"Even if it doesn't improve by 10, 15, 20 percent, they're not losing it and that's just as good."

Sharp says exercise is vital to prevent sarcopenia, and his research is intended to boost exercise results by providing nutritional support.

But it won't be a magic pill.

"There's no substitute for physical activity," he says. "We have to stay physically active through the lifespan.

"We think nutrition is a key component in helping to ensure that older adults get a better response from exercise."

Sharp is enlisting participants in his study, which will take several years to complete.