By Kerry Grens
NEW YORK (Reuters Health) - Programs aimed at preventing knee injuries among soccer players take time to make any lasting impact on the way athletes move, according to a new study.
A warm-up program of stretching and strengthening that lasted three months had only a temporary benefit, while the improvements seen after a nine-month program persisted for months after the training ended.
"Most injury prevention programs are probably for 10 to 12 weeks. Our thought is that if it stops after that point in time, within two to three months, that person is right back to where they began," said Darin Padua, lead author of the study and a professor at the University of North Carolina.
He and his team trained coaches for 15 youth soccer leagues to have athletes complete a 15-minute injury prevention program before practice for either three months or nine months.
At the beginning and end of the training period, the soccer players took a movement test, in which they leapt off a box, landed on the ground, then jumped straight upwards.
The movements during the test are good indicators of whether a person is at risk of hurting the anterior cruciate ligament (ACL) in the knee. For instance, if someone lands with a straight knee or points their toes inward or outward, they are considered to be at a higher risk of tearing the ACL, Padua said.
At the end of the training period, all the athletes scored better on the movement test than they did at the beginning of the study.
The players typically had about five or six errors on the movement test before the training, and three to four errors after the training. Padua said a score of five or above is typically the threshold for being at risk for an ACL injury.
"The types of errors are very obvious, so the fact that they were able to change one or two of those means they were able to make a pretty big change in their biomechanics," Padua told Reuters Health.
When Padua's group tested them three months after the training ended, only the players in the nine-month program retained these improvements.
"Sometimes the mistake we make from an injury prevention training stand point is once we see a person make some initial improvement in terms of how they're moving, we move on to other things or we quit," Padua said.
His group did not measure whether the improvements on the movement test actually reduced ACL injuries among the athletes.
But a recent study of young soccer and basketball players found that among those who participated in an injury prevention warm-up, there were 44 percent fewer non-contact injuries than among players who didn't get the training (see Reuters Health story of November 10, 2011).
Gregory Myer, a professor at Cincinnati Children's Hospital Medical Center, said that injury prevention training should be extended, especially into the preseason.
"There seems to be a high rate of injury in the beginning of the season," Myer said.
"One concern we have...is you get the dosage only at the start of the season, so they're playing during a period of high risk."
Female athletes are at a higher risk of ACL injuries than males, Myer, who was not involved in this study, told Reuters Health.
Damaging the ACL increases the chances of developing osteoarthritis later in life.
"These are going to be bad knees when these females are still young, in their 30s and 40s. That's one concern," he said.
The American Journal of Sports Medicine, online November 7, 2011.