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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Anterior cruciate ligament injuries in female athletes - part 2: a meta-analysis of neuromuscular interventions aimed at injury prevention

TE Hewett, KR Ford, and GD Myer.

Review published: 2006.

CRD summary

This review assessed the effectiveness of neuromuscular training interventions in reducing anterior cruciate ligament (ACL) injuries in female athletes. The authors concluded that there is evidence that neuromuscular training reduces ACL injury incidence in female athletes. Variation between the studies, small data sets and poor reporting of the review process limit confidence in these results.

Authors' objectives

To determine the effectiveness of neuromuscular training interventions in reducing anterior cruciate ligament (ACL) injuries in female athletes.


MEDLINE (1966 to 2004) and CINAHL (1982 to 2004) were searched; the search terms were reported. Abstracts were excluded from the review. Two of the included studies were published after the stated search date.

Study selection

Study designs of evaluations included in the review

Randomised controlled trials (RCTs) and prospective cohort studies were eligible for inclusion.

Specific interventions included in the review

Studies investigating neuromuscular training interventions for the prevention of ACL were eligible for inclusion. The interventions comprised between 18 and 108 sessions, for 10 to 75 minutes, over a period of 6 to 41 weeks. Trainers included a certified athletic trainer, a physical therapist, the coach, a team mate, oneself and an unspecified trainer. The interventions included plyometric movements (including high-intensity programmes), analysis of movement biomechanics and feedback, balance and stability training, and strength training, usually in combination.

Participants included in the review

Female athletes were eligible for inclusion. Trained and untrained basketball, football, volleyball and team handball athletes were included. Where stated, the ages of the participants ranged from 14 to 35 years.

Outcomes assessed in the review

The primary outcome was total ACL injuries. The review also assessed compliance with the interventions.

How were decisions on the relevance of primary studies made?

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.

Assessment of study quality

The validity of the primary studies was not formally assessed, although aspects of methodological quality were mentioned in the descriptions of individual studies.

Data extraction

The authors did not state how the data were extracted for the review, or how any discrepancies were resolved. Exposure rates and ACL injury incidence and non-contact ACL incidence (both per 1,000 exposures) were reported.

Methods of synthesis

How were the studies combined?

The studies were combined in a fixed-effect meta-analysis, weighted by sample size. Efficacy estimates (occurrence of ACL injury) were reported as a summary odds ratio (OR) with 95% confidence interval (CI).

How were differences between studies investigated?

Statistical heterogeneity was not quantitatively assessed. Differences between the studies were discussed with particular reference to components of the interventions.

Results of the review

Six studies were included (8,953 participants at most: in one study it was unclear if the numbers were reported more than once); total exposure (game and practice) was 573,896. There was one RCT (n=140), two prospective cohort studies (n=2,534), one case-control study (n=276) and two controlled cohort studies (n=6,003).

Methodological flaws in the studies included lack of statistical power, lack of randomisation, lack of reporting of compliance and inadequate description of ACL injury status.

The authors stated that three of the six studies found that neuromuscular training interventions significantly reduced the likelihood of ACL injury in female athletes, but the forest plot indicated that only one study reported a significantly reduced risk of ACL with the intervention compared with control. When estimates were pooled, neuromuscular training interventions were associated with a significant reduction in the risk of ACL injuries (OR 0.40, 95% CI: 0.26, 0.61).

Compliance rates ranged from 28 to 100% (based on five studies).

Components of effective interventions: all four studies that included plyometrics reported a reduced risk of ACL; three of these studies combined pylometrics with analysis of movement and feedback.

Cost information

Estimates of labour, equipment and total costs were reported foreach study. The total costs ranged from $0.5 to $375, most of which was explained by equipment costs.

Authors' conclusions

There is evidence that neuromuscular training reduces ACL injury incidence in female athletes, although it is not yet known what component(s) is(are) the most effective.

CRD commentary

The review question was supported by inclusion and exclusion criteria that were defined in terms of the study design, population and intervention. Only two electronic databases were searched, which may mean that not all relevant articles were retrieved. In addition, the authors made no attempt to locate unpublished material or to assess publication bias. The authors did not describe the process by which papers were selected for inclusion or the data were extracted, thus it is not possible to assess the likelihood of reviewer bias or error at these stages. The quality of the primary studies did not appear to have been systematically assessed, so the results from these studies and any synthesis might not be reliable.

The studies were quantitatively combined, which might not have been appropriate given the variation between the studies in terms of the intervention, population and study design. In addition, comparatively few events were reported (139 events in 8,953 participants). The authors acknowledged a number of limitations in their discussion, such as the lack of power in individual trials. Given the considerations highlighted, the results of this review should be interpreted with caution.

Implications of the review for practice and research

Practice: The authors suggested that neuromuscular training may assist in the reduction of ACL if plyometrics, balance and strengthening exercises are incorporated into a programme, training sessions are performed more than once a week, and the training programme is a minimum of 6 weeks long.

Research: The authors stated that further RCTs are needed and that future research should evaluate the relative efficacy of neuromuscular interventions, both alone and in combination.

Bibliographic details

Hewett T E, Ford K R, Myer G D. Anterior cruciate ligament injuries in female athletes - part 2: a meta-analysis of neuromuscular interventions aimed at injury prevention. American Journal of Sports Medicine 2006; 34(3): 490-498. [PubMed: 16382007]

Indexing Status

Subject indexing assigned by NLM


Adolescent; Anterior Cruciate Ligament /injuries; Female; Humans; Knee Injuries /epidemiology /prevention & control; Male; Muscle, Skeletal; Physical Fitness /physiology; Postural Balance; Sex Factors; United States /epidemiology



Database entry date


Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 16382007

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