Neuromuscular Warm-Ups Reduce Injuries in Female Athletes

Jennifer Garcia

November 07, 2011

November 7, 2011 — Coach-led neuromuscular warm-up training (NMT) reduces lower-extremity injuries in female high school basketball and soccer players in a low-income, mixed-ethnicity, urban setting, according to data from a large, cluster-randomized, controlled trial published in the November issue of the Archives of Pediatric and Adolescent Medicine.

To find out whether NMT training could reduce lower-extremity injuries in this setting, Cynthia R. LaBella, MD, from the Children's Memorial Hospital, Chicago, Illinois, and colleagues invited girls' soccer and basketball head coaches from all Chicago high schools to participate in the study during the 2006-2007 season. Of the 258 coaches invited, 95 enrolled, and 90 completed the study, representing 105 teams. The study was approved by the Chicago Public Schools research review board and the Children's Memorial Hospital review board.

After learning how to implement a 20-minute neuromuscular warm-up before team practices and a shorter pregame version, the coaches in the intervention group used the prescribed warm-up before an average of 80% (standard deviation [SD], 21%) of practices, with a median of 87%. The control coaches stuck to their standard warm-up protocol, including no warm-up exercises and having athletes jog or warm up on their own.

Overall, 96 lower-extremity injuries occurred (4.19/1000 athlete exposures; 95% confidence interval, 3.35 - 5.02 per 1000 athlete exposures) in the control group and 50 lower-extremity injuries (1.78/1000 athlete exposures; 95% confidence interval, 1.29 - 2.28 per 1000 athlete exposures) in the intervention group.

Compared with athletes in the control group, Dr. LaBella and colleagues noted a 44% decrease in acute noncontact lower-extremity injuries and a 34% decrease in noncontact ankle sprains among players in the intervention group.

Moreover, 7 athletes in the control group sustained anterior cruciate ligament (ACL) injuries during the study, and 6 of those required surgery. Two athletes in the intervention group sustained ACL injuries; neither required surgery.

NMT combines progressive strengthening with plyometric, balance, and agility exercises. Coaches instructed the athletes to avoid dynamic knee valgus and to land jumps with flexed hips and knees. The investigators taught coaches how to distinguish proper from improper form and how to use verbal cues to promote proper form.

The study authors calculated that 189 athletes would need to be trained to use neuromuscular warm-up exercises to prevent 1 noncontact lower-extremity injury. This would require training 11 soccer coaches or 16 basketball coaches, which, at $80 per coach per session, would be far less expensive than the estimated treatment cost for 1 surgically treated ACL injury.

A potential limitation of the study, the researchers note, is that it encompassed only 1 season, so whether compliance can be maintained for several seasons is unknown. In addition, parental consent to include personal health and background information was available for only 855 of the 1492 participating athletes; therefore the data may not be representative of the entire sample.

Despite the limitations, Dr. Labella and colleagues conclude: "[T]o our knowledge, this is the first randomized controlled study to demonstrate that (1) high school coaches in a mixed-ethnicity, predominantly low-income, urban population can implement a neuromuscular warm-up; (2) the warm-up reduces noncontact [lower-extremity] injuries, including ACL injuries, in female basketball and soccer athletes in this population; (3) the effect is likely dose related; and (4) coach training seems cost-effective."

M. Alison Brooks, MD, MPH, from the Department of Orthopedics and Pediatrics, and Timothy A. McGuine, PhD, ATC, from the University of Wisconsin Health Sports Medicine Center, University of Wisconsin–Madison, write in an accompanying editorial: "This study is indeed novel for targeting a group that is often ignored and understudied because of logistical barriers and lack of resources."

Although the study does confirm that neuromuscular training programs can reduce lower-extremity injuries, Dr. Brooks and Dr. McGuine point out that a longer follow-up would be needed to evaluate whether coaches continue to implement NMT consistently for several seasons, or whether retraining will be needed.

The editorialists also note that many of the coaches in the control group did not include any type of warm-up routine in their training. Whether this behavior extends to the large percentage of coaches who declined to participate in the study could provide qualitative information that may help identify barriers to successful implementation of injury prevention strategies.

Additionally, the authors of the editorial point out that including cost analysis of other, more common lower-extremity injuries beyond ACL would actually demonstrate an even greater cost-savings if coaches were trained in how to implement a neuromuscular warm-up as part of their training regimen.

Both the study authors and the editorialists point out that physical activity has significant benefits in adolescent girls, including improved academic success and lower rates of obesity, diabetes, pregnancy, and depression. This association underscores the importance of sports injury prevention, particularly in girls from mixed-ethnicity, predominantly low-income, urban populations who are at higher risk for adolescent obesity, diabetes, and pregnancy.

This study was supported by grants from Children's Memorial Research Center and Office of Child Advocacy. Dr. Brooks and Dr. McGuine have disclosed no relevant financial relationships.

Arch Pediatr Adolesc Med. 2011;165:1033-1040. Abstract

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