NEW YORK (Reuters Life!) - About a third of injuries that knock professional soccer players of the field are muscle-related, with many of these recurrent injuries that might have been avoided with adequate recovery, a Swedish study said.
Age and playing surface also have a role to play in muscle injuries serious enough to put players on the bench, according to the report published in the American Journal of Sports Medicine.
"Muscle injuries are a substantial problem for players and their clubs," said lead writer Jan Ekstrand at Linkoping University in Sweden.
"They constitute almost one third of all time-loss injuries in men's professional football, and 92 percent of all injuries affect the four big muscle groups in the lower limbs."
Ekstrand and his colleagues studied the injuries of about 2,300 players in three European soccer leagues over the years 2001 to 2009.
On average, players had slightly more than one muscle injury severe enough to be "unable to fully participate in training or match play" for every two seasons, with more than a third of the players missing a match or training session each season due to a muscle injury.
Nine out of ten such injuries involved the major muscle groups in the legs, particularly hamstrings. These usually came from a player running or kicking, and not from when they hit another player, said Robert Brophy, assistant professor of sports medicine at Washington University in St. Louis, who did not take part in the study.
"Contact's going to happen," said Brophy, noting that it was actually a good thing that most of the injuries were from running or kicking, since trainers and coaches can change workouts to try and reduce these injuries.
Injuries were about six times more likely in games than during practice and players aged 16 to 21 were less likely overall to get hurt than older players.
Only about a third of soccer injuries are from overuse, with the majority coming from a sudden pull or strain, Brophy added.
About one in six players were reinjured, which means a recovery period of up to 30 percent longer than with the first injury.
This can result from "trying to come back from injury too quickly," Brophy said, adding that the study's findings highlight the fact that players and trainers need to make sure players go through adequate rehabilitation before going back on the field.
Ekstrand and his colleagues said their results have implications for teams' abilities to reduce costly player down-time, while Brophy said it gave a better understanding of what muscles get hurt -- important because there are so many player injuries.
"It's going to be a common occurrence during someone's career as a pro soccer player," he said.
Reporting by Leigh Krietsch Boerner at Reuters Health; editing by Elaine Lies