Neuromuscular Training and the ACL
Abstract & Commentary
Synopsis: This prospective study demonstrates a decreased incidence of knee injuries in female athletes after completing a plyometric training program.
Source: Hewett TE, et al. The effect of neuromuscular training on the incidence of knee injury in female athletes. Am J Sports Med 1999;27(6): 699-706.
This is a prospective, nonrandomized, nonblinded study that determines the effect of a neuromuscular training program on the incidence of knee injury in high school athletes. A total of 1263 athletes participating in soccer, volleyball, and basketball were divided into three groups based on gender and willingness to participate in a plyometric training program (women trained with plyometrics, women not trained with plyometrics, and men not trained with plyometrics). A videotape demonstrating plyometric techniques was given to coaches and athletic trainers and the athletes were instructed in proper form by the trainers or physical therapists. Serious knee injuries, defined as ligamentous injuries resulting in five consecutive days of lost athletic time, were monitored. Anterior cruciate ligament (ACL) tears were confirmed by arthroscopy, and medial collateral ligament (MCL) tears were diagnosed by examination alone. Grade I MCL sprains were not considered a serious knee injury and were excluded. Only primary knee injuries were included in the analysis.
The training program consisted of workouts held three times per week using the neuromuscular training program. All athletes in the plyometric group completed a four-week session and most completed a six-week program. The neuromuscular program—provided in a detailed outline in the article—involves flexibility, plyometrics, and weight training to increase muscle strength and decrease landing forces during jumping.
Fourteen serious knee injuries were reported through the soccer, basketball, and volleyball seasons. Ten of 463 untrained female athletes, 2/366 trained female athletes, and 2/434 male athletes sustained serious knee injuries. Chi-square testing identified statistically significant differences in injury rates between the trained and untrained female groups, between the untrained female group and the male group, but no difference between the trained female group and the male group. The incidence of non-contact injuries was significantly lower in the trained vs. untrained groups.
Comment by James R. Slauterbeck, MD
To my knowledge, this is the first prospective study to demonstrate the positive effects of a plyometric program on decreasing injury rates in running and cutting sports in high school athletes. Clearly, women athletes are at a greater risk for ACL injury than male athletes. Many hypotheses for this gender difference have been proposed and are being tested.
This study shows that women participating in a neuromuscular training program had a lower incidence of serious knee injury than those not participating in the program. In addition, the trained women had a similar injury incidence to men. Although other training techniques were not controlled, I believe this study adequately demonstrates that neuromuscular training can benefit the female athlete.
This study could be improved if it were double blinded and randomized. The teams themselves decided if they wanted to be in the program. I must admit that it would be difficult to convince a coach that his or her team’s training program was going to be decided by the toss of a coin. Also, it would be difficult to standardize all other training techniques taught by each individual coach. Controlling the numbers of athletes in each group would help this study and could be done rather easily. Increasing the numbers of athletes in the study and controlling the numbers of athletes in each group from each sport would be a nice addition to the current project.
All in all, I think this project was well done and adds to our knowledge base. Neuromuscular training programs using plyometric exercise when monitored by knowledgeable instructors can help many athletes. I am concerned that some plyometric programs, if used without appropriate guidance, will cause a new set of injuries including stress fractures and other overuse injuries to the lower extremities. I would recommend careful review of this article and discussion of the techniques with appropriate coaches and trainers before adopting the given techniques as gospel. Potentially, many women’s programs then could benefit from neuromuscular training to help decrease the incidence of serious knee injuries.
The incidence of ACL tears in running and cutting athletes can be decreased by:
a. adjusting the serum sex hormone levels in athletes to better remodel soft tissue ligaments.
b. performing prophylactic notchplasty on uninjured knees after ACL injury is identified on the other side and arthroscopy or MRI identifies a narrow notch.
c. using a strength, stretching, and plyometric exercise program.
d. All of the above
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