Hamstring Strain Injury (HSI) Prevention in Professional and Semi-Professional Football Teams: A Systematic Review and Meta-Analysis

Hamstring Strain Injuries (HSIs) are the most common type of lesion in professional footballers and the leading cause of absence days from sports. However, recent studies have shown that high-level football teams apparently do not apply any HSI prevention protocol. The aim of the study was to determine the effect of preventive strategies and protocols in reducing the incidence of hamstring muscle injuries in professional and semi-professional football teams. A literature search of PubMed/MEDLINE, ISI/Web of Science and Scopus databases was conducted with the keywords "hamstring* and (injury* or strain) and prevent* and (soccer or football)". Quality and bias assessment was completed through the Kennelly modified scale. The Injury Incidence Rate (IIR) and the Incidence Rate Ratio (IRR) were assessed in the statistical analysis. In the meta-analysis, data were extracted, pooled and analysed with "Comprehensive Meta-Analysis Version 3.3.070" software. In total, 8 of the 1017 original search studies met the inclusion criteria of this review. The total exposure of the studies was 170,221.8 h, while the number of HSIs recorded was 165 in the intervention groups and 224 in the control groups. The average score of the quality assessment was 23.6/34. The meta-analysis of six of the eight included studies provided strong evidence that interventions are effective in reducing hamstring injuries. The IRR of the effect size was 0.443, with p-value = 0.001. The studies analysed applied different preventive strategies: the Nordic hamstring exercise, the FIFA 11+ programme and exercises for core stability or balance training. All these interventions proved to have a successful effect on prevention of hamstring injuries.