NEW YORK (Reuters Health) - Competitive surfing is safer than college-level soccer, football and even basketball -- as long as big waves, shallow reefs or rocky bottoms aren't involved.

"It's a relatively safe sport, especially if you're surfing in the places most people surf, in the sort of sandy bottom places," Dr. Andrew Nathanson of Rhode Island Hospital in Providence, the study's lead author, told Reuters Health.

Nathanson and his team looked at 32 professional and amateur surfing competitions worldwide between 1999 and 2005. They calculated that there were 6.6 serious injuries for every 1,000 hours of surfing, a rate well below that seen in professional rugby (69 per 1,000 hours), men's college soccer (18.8 per 1,000 hours) and men's college basketball (9 per 1,000 hours).

However, the injury rate more than doubled when the waves were over the surfers' heads or if surfing took place over a rocky or reef bottom.

In a later analysis of competitions at Hawaii's Pipeline, an area with notoriously huge and hollow waves, Nathanson found a much higher injury rate of 37 per 1,000 hours of surfing, he noted in an interview with Reuters Health. Still, surfing at this particular spot was just "slightly more dangerous than college football," he added, in which players suffer 33 injuries for every 1,000 hours of play.

Most of the injuries among these competitive surfers involved strains and sprains to the leg, especially knee injuries, which accounted for nearly 20 percent of all injuries. Knee injuries were typically the result of aerial moves or turns; for example, jumping in the air off a wave or turning sharply and aggressively, which Nathanson and his team note are moves that "score highly in competition."

In a past study of recreational surfers, Nathanson and his colleagues found most injuries were not strains and sprains due to such "powerful and acrobatic maneuvers," which are beyond the capacity of most non-competitive surfers, but cuts, bruises and scrapes from the surf board itself and collisions with other surfers.

While surfers enjoy a fairly empty field during competition, he noted, recreational surfers may have to share the waves with dozens of others.

To reduce the injury risk, Nathanson noted, recreational surfers can use boards with a more rounded nose and rubberized fin edges, and should also be physically fit and strong swimmers. A good understanding of the surfing spot is also key, Nathanson added, so surfers can avoid submerged hazards like rebar, strong currents, and even sharks and jellyfish.