The mid-air grabs of wide receivers, the elegant sprints of defensive secondaries, and the gaping kicks of special teams players make them the most vulnerable football players to suffer hamstring strains. And a new study shows more than half of those injuries happen before they ever get to a regular season game.

“It’s pretty striking,” said Dr. Marcus Elliott, the founder and director of Peak Performance Project, a Santa Barbara, California-based institute that works with elite athletes. “There is a huge number of injuries that occur during the first few weeks of training.”

Elliott and his colleagues extracted hamstring injury reports from the National Football League’s Injury Surveillance System, collected from 1989 to 1998. More than half of the strains - 904 - occurred during the shorter preseason, which lasts 7 weeks, compared to the 16-week regular season.

The report, published in the American Journal of Sports Medicine, shows a spike of injuries during July and August. That means athletes are losing condition during the off-season, Elliott told Reuters Health.

Dr. Brian Halpern, who treats athletes with muscle injuries at the Hospital for Special Surgery in New York and who was not involved in this study, said the findings make sense.

“You’re out of condition, you’re out of flexibility, and then you get into this aggressive program of running, cutting, and sprinting,” he told Reuters Health. The study “confirmed what we clinically see.”

In total, players suffered more than 1,700 hamstring injuries over the 10-year period. An earlier study found hamstring pulls were one of the most common maladies in pro football, second only to knee sprains.

“Is it a plague? It is if you realize that a lot of them are preventable,” Elliott said.

Just one in five of the muscle traumas were the result of contact, the researchers found; the rest happened from running, jumping, and kicking, illustrating just how preventable these injuries are.

Prevention involves more than strengthening the muscle, Elliott said. Balance, running mechanics, strong trunk muscles, and proper timing of the hamstring’s activity during motion are all important.

“Eccentric” training (pronounced ee-centric) appears to help protect the hamstring, Elliott added. It involves motions that stretch the muscle as it is contracting. For instance, using one leg to repeatedly jump up and down on a step will contract and stretch the hamstring.

Hamstring pulls don’t have the potentially devastating consequences of head injuries - which can be career-ending or permanently damaging - but Elliott’s study shows that athletes pay the price for early-season strains. One in five injuries in the regular season, 155 over the 10 years, were re-injuries.

This study is the most extensive look at the patterns of hamstring injury in professional football, Elliott said. NFL Charities, a non-profit founded by the NFL teams, funded the research.

Elliott proposes developing more personalized off-season exercise programs that identify players most at risk of hamstring injuries, and getting them into proper prevention training.

SOURCE: The American Journal of Sports Medicine, online February 18, 2011.