Age-specific protocols are key to success
By Emily Delzell
Training programs aimed at preventing anterior cruciate ligament injuries have been used for many years, but injury rates remain high. Injury prevention experts suggest such programs may be more effective if implemented before children reach the ages associated with highest injury risk and if the programs utilize age-specific protocols.
Adolescents aged 16 to 18 years appear to be at the highest risk for ACL injuries, but the frequency of these events begins increasing when children are aged 10 to 12 years, says Lindsey DiStefano, PhD, ATC, assistant professor in the Department of Kinesiology at the University of Connecticut in Storrs.
“ACL injuries are relatively uncommon in younger children, but when they start taking part in organized sports they exhibit movement patterns during landing and cutting tasks that are associated with heightened ACL injury risk,” she said.
These risky patterns include decreased knee flexion, knee valgus, and excessive leg rotation, DiStefano said.
Researchers from Cincinnati Children’s Hospital Medical Center, where much of the early work on ACL prevention was done, reported in October that development of high risk movement patterns begins in early puberty.1
“We know young children are much more plastic in their adaptive abilities than adults and think there are windows of opportunity to address this prior to puberty,” said Greg Myer, PhD, a research instructor of sports medicine in the Human Performance Laboratory at CCHMC.
Several recent studies have examined the effects of age-specific ACL injury prevention training, including two randomized controlled trials (RCTs) conducted by DiStefano and colleagues.
“Previous research suggests injury programs that deliver injury-prevention benefits in high school and college-aged athletes don’t work in younger children,” she said.
A 2009 study by DiStefano and colleagues, for example, found that an injury prevention program focused on landing biomechanics in two age groups of children produced greater improvements in the older group (aged 14-17 years) than in the younger children (aged 10-13 years), despite the fact that training time was more than twice as long in the younger group.2
In a more recent trial looking at the effect of injury prevention programs on lower extremity biomechanics during cutting tasks, DiStefano and colleagues randomized 65 youth soccer players (38 boys, 27 girls; mean age 10±1 years) into three groups: a pediatric ACL injury prevention program, a traditional program, and no training. Authors hypothesized that the age-specific program would increase knee and hip flexion and reduce knee valgus and knee and hip rotation.3
“The pediatric and traditional training programs both focused on quality of exercises, i.e., performing movements correctly rather than going through the motions, but the pediatric program also emphasized progressive exercises, taught smaller task components with increased instruction time, and involved more frequent feedback and exercise variety,” DiStefano said.
Results, published in May in the American Journal of Sports Medicine, found the traditional program produced no change in cutting biomechanics while the pediatric program modified only knee external rotation.
“The children didn’t respond as well as hoped, but there are a couple factors to consider,” DiStefano said. “First, there’s not a lot of evidence that training programs can affect cutting biomechanics in adults. Second, the program did modify knee rotation, which may be an important change. We still don’t clearly understand the proven factors for ACL injury. It may be that knee rotation during cutting is a major factor in load on the ACL.”
A second RCT conducted by DiStefano et al examined the effects of an age-specific program on landing biomechanics in 59 youth soccer athletes (34 boys, 25 girls; mean age 10±1 years). Investigators randomized children to the same three groups as in the cutting trial and found that while the traditional program had no effect, the pediatric program significantly increased peak knee flexion and decreased peak vertical ground reaction force compared with the control group.4
“Taken together, these data suggest age-specific training in younger children is more effective than traditional programs,” DiStefano said. “It may be more difficult to alter biomechanics during more dynamic activities, such as cutting tasks, but if we start intervening when children are younger and can make significant changes in jump-landing tasks then there’s additional time to refine their more dynamic movements before they reach the age of highest injury risk.”
1. Ford KR, Shapiro R, Myer GD, et al. Longitudinal sex differences during landing in knee abduction in young athletes. Med Sci Sports Exerc 2010;42(10):1923-1931.
2. DiStefano LJ, Padua DA, DiStefano MJ, Marshall SW. Influence of age, sex, technique, and exercise program on movement patterns after an anterior cruciate ligament injury prevention program in youth soccer players. Am J Sports Med 2009;37(3):495-505.
3. DiStefano LJ, Blackburn JT, Marshall SW, et al. Effects of an age specific anterior cruciate ligament injury prevention program on lower extremity biomechanics in children. Am J Sports Med 2011;39(5):949-957.
4. DiStefano LJ, Padua DA, Stephenson LJ, et al. A pediatric ACL injury prevention program improves landing biomechanics in youth soccer athletes. J Athl Train 2010;45(3 Suppl):S48-S49.