Neuromuscular Training Decreases ACL Injury Risk in Females

Abstract & Commentary

Synopsis: The study found that it is possible to prevent ACL injuries with successful completion of a specific neuromuscular training program. This is confirmation of prior studies that neuromuscular training can decrease ACL injury rates in female athletes.

Source: Myklebust G, et al. Prevention of anterior cruciate ligament injuries in female team handball players: A prospective intervention study over three seasons. Clin J Sport Med. 2003;13(2):71-78.

Neuromuscular training is being used in an attempt to decrease injury and enhance performance in female athletes participating in high-risk sports like basketball and soccer. Myklebust and colleagues instituted a prospective study assessing the effect of a neuromuscular training program on the incidence of ACL injuries in Norwegian female team handball players. The top 3 Norwegian divisions were studied during a 3-year period. Myklebust et al used an initial season without intervention to determine injury rate, which they term the "control season," which included 942 players (1998-1999). The next year, the first intervention season, included 855 players (1999-2000), and the third year, the second intervention season, included 850 players (2000-2001). The neuromuscular training program involved 3 different balance exercises focusing on neuromuscular control and planting/landing skills.

The teams were supplied with an instructional video, balance mats, and wobble boards. A physical therapist was assigned to every team to assist the athletes. The success of the program was measured by identifying the number of ACL injuries during the seasons. Twenty-nine ACL injuries were reported during the control season, 23 injuries during the first intervention season, and 17 injuries during the second intervention season. When normalized to injury exposures (player-hours), ACL injury risk decreased 36%. These decreases per season were not statistically significant. However, when the athletes were separated by division, in the elite division there were 13 injuries during the control season, 6 injuries during the first intervention season (P = .17), and 5 injuries in the second intervention season (P = .06). Among those who met the compliance criteria (at least 15 of 21 possible training sessions), there was a significant drop in injury rates (P = .01). In addition, about half of the ACL injuries were noncontact injuries. When Myklebust et al separated out the contact injuries, they observed 18 injuries in the control season and 7 in the second intervention season (P = .04).

Comment by Timothy E. Hewett, PhD

This is a very well-done prospective study. I think we can learn much from Myklebust et al’s innovative approach. They should be commended for their analysis of compliance, which hasn’t been well addressed in this literature previously. Their data demonstrate what a challenge compliance is, even with athletes of high caliber, as only 26% of the teams were judged compliant the first year and 29% the second year of intervention.

There appears to be a consistent effect of neuromuscular training on ACL injury rates. The jury is still out, however, concerning the contribution of hormonal fluctuation to ACL injury risk. Myklebust et al found evidence of higher risk during menses, whereas others have reported the ovulatory and luteal phase of the cycle to be the higher-risk phases.

A few weaknesses/limitations to the study were methodological in nature. They included a lack of sufficient documentation of ACL injury status, adjustment of all menstrual cycles to 28 days without an explanation of the method for adjustment, and not enough detail on statistical testing. In addition, Myklebust et al make several references to insignificant results without performing a power analysis for the study. A power analysis should have been performed to determine if the lack of significance was likely due to an insufficient number of subjects.

Dr. Hewett is Director and Assistant Professor, The Sports Medicine Biodynamics Center, University of Cincinnati College of Medicine, Cincinnati, OH.