Men who exercise more have better erectile and sexual function, suggests a small study of older overweight men.

The authors say their results support the idea that exercise might one day be prescribed as a treatment for erectile dysfunction.

While previous research has linked erections to physical activity, the current study is the first to include a high proportion of African-Americans and finds they get the same apparent benefit from exercise as white men.

"Our results confirm previous work, however, no study has ever addressed how a minimal amount of exercise impacts both erectile and sexual function among black men, a population with increased prevalence of erectile dysfunction risk factors including obesity, diabetes, sedentary lifestyle and lower socioeconomic status," senior study author Adriana Vidal, a researcher at the Cedars-Sinai Samuel Oschin Comprehensive Cancer Institute in Los Angeles, said in an email.

Vidal and colleagues examined exercise habits and sexual function in 295 healthy men who were part of a research project evaluating prostate cancer risk at the Durham Veterans Affairs Medical Center in North Carolina.

On average, the men were about 62 years old, and they were all overweight or obese. Roughly one third had diabetes or a history of chest pain or heart attacks. About three quarters were current or former smokers. Ninety-three men, or about a third of the group, were African-American.

Researchers asked the participants how often they exercised, and how intensely, as well as what types of physical activities they did. Men were scored based on a measure known as metabolic equivalent of task (MET) hours per week and placed in four categories ranging from sedentary, with three or fewer MET hours/week, to highly active, with at least 18 MET hours/week.

Most often, the men were sedentary, with 44 percent reporting little activity. But a substantial proportion, 26 percent, were highly active.

Researchers also questioned the men about their sexual function, focusing on their ability to get erections and have orgasms, as well as the quality and frequency of their erections.

Men rated their functionality on most questions from 1 to 5, with higher numbers equaling more satisfaction. Added up, responses could lead to a total score from 0 to 100.

For all participants, the average sexual satisfaction score was 50.

Men who reported more frequent exercise also reported higher sexual function scores. Half of the highly active men reported sexual function scores of at least 70, compared with a median score of about 33 for sedentary men.

The study is relatively small, and only looked at one point in time, so it wasn't designed to prove that men can improve sexual function by getting more exercise, the researchers write in The Journal of Sexual Medicine.

The men in the study were also not that active, noted Dr. Joan Khoo, chief of endocrinology at Changi General Hospital in Singapore, in an email.

To get the minimum amount of exercise needed to qualify as highly active in the study, men would need to do a moderately intense activity such as brisk walking, cycling or tennis for an hour three to four times a week, said Khoo, who wasn't involved in the study.

Still, Khoo said, many factors besides exercise can contribute to sexual function.

"In addition to genetic differences, disparities between ethnic groups in psychological, cultural and socioeconomic barriers to diet and exercise may contribute to the observed association and benefit (or lack thereof) between ethnicity and erectile function," Khoo said.