Muscle fibre typology as a novel risk factor for hamstring strain injuries in professional football (soccer) : a prospective cohort study

Background : Hamstring strain injuries (HSI) are prevalent in team sports and occur frequently in the latter phase of matches. In the search for interindividual factors that determine muscle fatigue and possibly injury risk, muscle fibre typology is a likely candidate. It was the aim of the study to determine whether muscle fibre typology is a risk factor for HSI. Methods : A prospective cohort study was conducted over 3 seasons in professional football players competing in the Belgian Jupiler Pro League (n=118) and in the English Premier League (n=47), and a total of 27 hamstring strain injuries were sustained during this period. The muscle fibre typology was non-invasively estimated using proton magnetic resonance spectroscopy, and was characterized as a fast, slow, or intermediate typology based on the carnosine concentration in the soleus. A multivariate cox model was used to identify risk factors for HSI. Results : Football players exhibit a wide variety of muscle typologies (slow typology=44.9%; intermediate typology=39.8%, fast typology=15.3%). In the combined cohort, players with a fast typology displayed a 5.3-fold (95% CI 1.92-14.8, P=0.001) higher risk than slow typology players to sustain an index HSI. This was also independently observed in both leagues separately as respectively a 6.7-fold (95% CI 1.3-34.1; P=0.023) and a 5.1-fold (95% CI 1.2-20.4; P=0.023) higher chance was found in fast typology players than slow typology players of the Jupiler Pro League and the Premier League cohort. Conclusion : We discovered muscle fibre typology as a novel and potent risk factor for HSI in team sports.