Injuries are more common in football compared to most other types of sport and numerous studies have been carried out to investigate the type, location, and severity of injuries in football. Several studies have also examined selected potential intrinsic (person-related) or extrinsic (environment-related) risk factors, whereas injury mechanisms rarely have been studied. These studies have shown that intrinsic risk factors such as increased age, career duration and previous injury seem to
increase the risk of injuries.
Risk Factors for Hamstring Strains
The players who incurred hamstring strains in the study period were significantly older, and there was a trend toward higher body fat percentage than in the group without hamstring strains. A history of a previous strain was a significant risk factor for a new strain on the same side during the study period (Fig. 2). Also, when risk factors were treated as categorical variables, the oldest group of players (>1 SD above mean, 29 to 38 years) had a significantly higher risk of a hamstring strain than the intermediate group (P = 0.02). In the multivariate logistic regression analysis (where previous injury, age, weight, and body fat were included), age and previous hamstring strains were found to be significant predictor variables .
Risk Factors for Injury
Most studies on risk factors for football injuries have used a univariate analysis to compare injured and noninjured groups of players. Because of the complexity of risk factor analysis and possible interaction between different risk factors, a multivariate model has been recommended. The main risk factors identified in the present study were previous injury and age, and the multivariate tests showed that although there was some confounding, both factors influence injury risk. Previous injury is associated with increased age but is also an independent risk factor for injury. Previous studies have reported conflicting results on age as a risk factor, some finding that older players are more prone to injury and others not. Previous studies on football players have reported a high rate of recurrent hamstring strains and groin strains, as well as knee and ankle sprains.
In the present study, a previous strain or sprain on the same side was found to be a strong predictor for a new injury. In the case of adductor or hamstring strains, this may be due to changes in the structural or scar tissue formation in the muscle or tendon after injury or inadequate rehabilitation as well as too early a return to competitive physical activity after the previous strain.
