Having an active day can help keep colds away.

That's what researchers at the University of South Carolina found in a year-long study of 547 healthy men and women.

The people who were more active in the study averaged one cold in a year, about 23 per cent lower than the least active group, the study reports.

"I feel the evidence is so compelling that I think people can use it as a reason to be active," said David Nieman, a researcher from Appalachian State University who was not involved in the study.

The study based levels of activity on recommended minimums from the U.S. Surgeon General. The guidelines suggest 30 minutes of such activities as a brisk walk or lawn mowing most days of the week

Nieman said physical activity stimulates immune cells, which help fight colds. Regular activity boosts the immune system which lowers the risk of catching a cold.

But Nieman said very hard exercise can work against the immune system. For instance, people who run a marathon have a higher risk of catching a cold following the intense exercise.

And Nieman does not consider exercise as a means to cure a cold.