WASHINGTON — Nearly 40 percent of NFL players last season wore a helmet model that got the second-lowest rating for reducing the risk of concussions in a study by Virginia Tech researchers.

Riddell’s VSR-4 helmet received just one star in a study of football helmets led by Virginia Tech professor of biomedical engineering, Stefan Duma and released Tuesday.

Another Riddell model — the Revolution Speed — was the only helmet that earned five stars, the top rating.

Five models — two made by Riddell, two by Schutt and one by Xenith — received four stars.

According to Riddell, 38 percent of NFL players wore the low-rated VSR-4 in 2010. The company also said 39 percent wore one of the various models that fall under the Riddell Revolution name or the new Riddell 360.