Allowing snowboarders to hit the slopes at one U.S. ski resort led to a small rise in the number of overall injuries, a trend in line with findings at ski areas elsewhere, according to a U.S. report.

Injuries rose by 13 percent in the two years after snowboarders were permitted at the Taos Ski Valley in New Mexico, compared to the two years before, according to the report in The American Journal of Sports Medicine.

"We recognize that a small but statistically significant increase in injury rate was observed after the addition of snowboarding to this mountain but that factors other than type of sport may play a role in the differences that were identified," said study leader David Rust from the University of new Mexico in Albuquerque.

Rust and his team looked at records from the Mogul Medical Clinic at Taos Ski Valley and compared the injuries that happened before and after snowboarding was first allowed in March 2008.

Overall, the rate of injuries increased from about 207 per 100,000 visits to the mountain in the 2006 to 2007 winter season, to about 234 injured per100,000 in the 2009 to 2010 season.

"If you did that (study) at 10 different mountains, the trend would be the same," said Robert Johnson, from the University of Vermont College of Medicine in Burlington.

The rise was due mostly to an increase in the kind of upper body injuries that are most common among snowboarders, such as wrist sprains and fractures. Broken wrists jumped from the then most common injury before snowboarders were allowed to the second most common at the end of the study.

On the other hand, lower body injuries that are most typical among skiers, such as anterior cruciate ligament or ACL tears, and knee sprains, remained constant.

During the study period, the number of visitors to the mountain also rose, from an average of 1,610 per day during the 2006 to 2007 season until March 2008, to 1973 visits per day from March 2008 to the end of the 2009 to 2010 season.

The average age of injured people dropped, from 39 years old without snowboarders to 31 with them.

The researchers were unable to say why the number of injuries increased, but previous research suggests snowboarders are more injury-prone than skiers.

Last year, Johnson and his colleagues found that snowboarders accounted for 19 percent of injuries at one ski mountain in Vermont, but only made up 17 percent of athletes on the slopes.

The new report avoids suggesting that snowboarding is the more dangerous sport, or that skiers are taking more risk by sharing the slopes, and suggests that other factors than the type of skiing may play a role.

These may include that snowboarding has brought in a younger group of people, who tend to take more risks, as well as raising the overall number of people on the slopes, the researchers said.