Knee Warm-Ups

Pick an option: the prospect of months on crutches and a season on the sidelines, versus taking 10 minutes to do a short, simple, structured warm up. For athletes, particularly school-aged athletes, the choice should be clear.

What’s more, the choice appears to be even clearer for young players whose movements and biomechanics make them more susceptible than their teammates to potentially devastating knee injuries, according to a study involving young soccer players conducted by researchers at the University of North Carolina at Chapel Hill.

“Soccer players and other young athletes have a fairly high incidence of injuries, especially involving the anterior cruciate ligament, or ACL, a ligament critical for knee stability,” said Darin Padua, Ph.D., associate professor of exercise and sport science in the UNC College of Arts and Sciences. “For some reason, girls seem to be at greater risk of ACL injuries. You hear about a lot of these injuries in basketball, too.”

Padua and his team from the exercise and sport science department and from the UNC Gillings School of Global Public Health worked with the Triangle United Soccer Association and 173 youth soccer players (boys and girls, ages 10-17) on 27 teams in Durham and Chapel Hill, N.C., to see how their movements might contribute to injury risk. They videotaped the players jumping and landing, both before a new warm-up routine was introduced, and afterwards, to see what changes had occurred.

They found that those who had the poorest movement quality at the beginning of the study were the most likely to benefit from the exercises, according to the study, published in the March issue of the American Journal of Sports Medicine.

The intervention involved warm-up activities designed to increase players’ flexibility, balance and strength, as well as their foot planting, jumping and cutting skills, since previous research has shown that approximately 70 percent of ACL injuries are the result of such noncontact movements. The routine took 10 to 12 minutes before every game and practice, and was used in place of the jogging and stretching warm ups the players had been using previously. Details about the exercises are available at http://www.unc.edu/sportmedlab/publications.htm (under the “Knee Injury” section); or at http://www.unc.edu/sportmedlab/docs/knee/distefano/Appendix%201.pdf and http://www.unc.edu/sportmedlab/docs/knee/distefano/Appendix%202.pdf.

“The players who had the poorest movement quality at the start of the study — those who landed stiff-kneed or knock-kneed when they jumped, or who landed on their heels or one foot before the other — benefitted the most from the intervention,” Padua said. “This was true for both boys and girls.”

“This shows that warm-up exercises that enhance flexibility, balance and strength can double as injury prevention programs by successfully modifying players’ movements,” he said.

The study was designed to see if a general, or “one-size-fits-all,” warm-up routine was effective for all team members, or if individualized programs were more effective. They found similar results for players in both the general and individualized programs. Both were effective, Padua said.

Researchers also noticed that the older children in the study responded better to the warm-up exercises than the younger ones did.

“That’s a take away from this study,” Padua said. “The younger kids may need to be trained differently. Things that are successful in older populations may not work in younger children.”

Other authors on the paper, all from UNC, are Lindsay DiStefano, doctoral candidate in human movement science; Michael DiStefano, social research specialist in exercise and sport science; and Stephen W. Marshall, Ph.D., associate professor of epidemiology.

For more information, visit: www.unc.edu/sportmedlab or http://ajs.sagepub.com/.