THURSDAY, Jan. 29 (HealthDayNews) -- Professional soccer teams in England miss the equivalent of 15 games and 90 training days every season because of player hamstring injuries, says a study in the British Journal of Sports Medicine.

Researchers from the Football Association Medical Research Programme audited soccer play injuries suffered during games and practices over two seasons, from July 1997 to the end of May 1999. Complete injury records were obtained for 87 percent (first season) and 76 percent (second season) of 91 teams.

They found hamstring injuries accounted for 12 percent of all injuries sustained over the two seasons. Each team had an average of five hamstring injuries per season. As a result of these hamstring injuries, a total of more than 13,000 training days and 2,000 games were missed. That equals 18 training days and three games missed for every hamstring strain.

Each team missed on average of 90 training days and 15 games due to hamstring injuries each season.

The study found that one in three hamstring injuries was suffered during practice and two-thirds occurred during games. In 57 percent of the cases, the injury was sustained while running and most often near the end of each of the game halves.

The hamstring re-injury rate was 12 percent, which the study authors said was high. They note that players returning too soon to competitive play after suffering a hamstring injury may be the reason for that high re-injury rate.

The hamstrings are tendons at the back of the knee. Hamstrings connect to the muscles that flex the knee joint.

More information

Here's where you can learn more about hamstring injury.