Male professional rugby players with hamstring/quadriceps muscle imbalance have an increased risk of hamstring injuries during the season

Background: Hamstring injuries (HI) are among the most common muscle injuries in team ball sports. Hamstring strenght deficit is an intrinsic risk factor for HI. To evaluate the rate of occurrence of HI in male professional rugby “Top 14” players during one season and to study the possible relationships among hamstring strength deficit (evaluated by isokinetic dynamometry), muscle extensibility defects, field position and the risk of HI. Study Design: Descriptive epidemiology study. Methods: The rate of HI was prospectively studied in 134 professional rugby players from four French professional teams over one competitive season. Preseason isokinetic and muscle extensibility tests were performed. The recorded information included the field position and history of injuries. The analysis was performed by comparing two groups: without (Group A) and with (Group B) preseason isokinetic imbalance. Results: During the season, the rate of HI was 29.9% (95% CI: 22.2-38.4%), with fewer injuries in Group A than in Group B (21.0%, 95% CI: 11.6-33.2% versus 37.5%, 95% CI: 26.3-49.7%, respectively). According to the multivariable analysis, Group B had an increased risk of HI compared with Group A (OR: 2.65, 95% CI: 1.08-6.44, p=0.032 ), as did the players with a history of HI (OR: 2.96, 95% CI: 1.06-8.28, p=0.039 ), whereas the players’ field position was not significantly associated with HI. Conclusion: The rate of HI among professional rugby players is high. An isokinetic imbalance in the preseason is a risk factor for injury during the season. This knowledge can be used to implement prevention strategies in professional sports. Clinical trial number : Not applicable