Eccentric training for prevention of hamstring injuries may depend on intervention compliance: a systematic review and meta-analysis

Abstract

Background Hamstring injury is a prevalent muscle injury in sports. Inconclusive evidence exists for eccentric hamstring strengthening to prevent hamstring injuries. One reason for this discrepancy may be the influence intervention non-compliance has on individual study estimates, and therefore pooled estimates. Objective This systematic review aims to determine the effect of eccentric hamstring strengthening on the risk of hamstring injury and quantitatively explores the impact of intervention non-compliance on the precision, heterogeneity and strength of pooled estimates. Methods A computer-assisted literature search of Medline, CINAHL, Cochrane, EMBASE, AMED, SportDiscus and PEDro databases was conducted with keywords related to eccentric strengthening and hamstring injury. The search was conducted from the end of a previous comprehensive review forward (1 December 2008 to 31 December 2013). Randomeffects models were used for both main effects and a sensitivity analysis. Pooled estimate precision was measured with a confidence limit ratio (confidence limit ratio (CLR); upper limit divided by the lower limit) and heterogeneity was assessed with I 2 , Cochrane's-Q and τ 2 . A protocol was not registered for this review. Results Four out of 349 studies met the inclusion criteria. In main effects analysis, eccentric hamstring training did not reduce the risk of hamstring injury (risk ratio [RR]=0.59 ((95% CI 0.24 to 1.44)). This estimate was imprecise (CLR=6.0) with significant heterogeneity ( p value 0.02, 69.6% variation and t 2 =0.57). Subjects compliant with eccentric strengthening had a significant (RR=0.35 ((95% CI 0.23 to 0.55)) reduction in hamstring injuries. This estimate was precise (CLR=2.4) and homogenous ( p value=0.38, 2.8% variation and t 2 =0.007). Conclusions The null-biased effect in using intent-totreat methods from intervention non-compliance has a substantial impact on the precision, heterogeneity and the direction and strength of pooled estimates. Eccentric strengthening, with good compliance, appears to be successful in prevention of hamstring injury.

Impact of exercise selection on hamstring muscle activation

“…The Nordic hamstring exercise is effective15 16 18 in reducing HSIs in soccer players as long as compliance is adequate 37 38. However, we11 and others22 have previously reported that the Nordic preferentially activates the semitendinosus, and this might be interpreted as evidence that the exercise is suboptimal to protection against running-related strain injury which predominantly effects the BF LongHead .…”

Evidence-based hamstring injury prevention is not adopted by the majority of Champions League or Norwegian Premier League football teams: the Nordic Hamstring survey

“…This suggests that completing this exercise progression may be critical for programme efficacy. A recent systematic review on the efficacy of the NH programme and other eccentric interventions also documents that programme compliance is essential, showing a 65% reduction in hamstring injury risk among highly compliant participants, with no effect when including less compliant participants 34. In the current study, clubs reported doing no initial NH training or no maintenance training for 95 of the 150 seasons included (see table 2); we therefore feel confident in concluding that the vast majority of teams did not use the NH programme as prescribed.…”

Clinical Practice Patterns and Beliefs in the Management of Hamstrings Strain Injuries

“…48 On the contrary, we observed a high level of use for concentric strengthening, which does not appear to be recommended and may even be deleterious during HSI rehabilitation. 49 Whereas eccentric training has been shown to cause protective adaptations by allowing increased strength at longer muscle lengths through an increase in the number of sarcomeres in series, [50][51][52][53] concentric strengthening results in a decrease in sarcomeres in series.…”