Relationship of Pre-Season Strength Asymmetries, Flexibility and Aerobic Capacity with In-Season Lower Body Injuries in Soccer Players

The present study aimed to assess the differences in pre-season knee strength asymmetries, flexibility, and aerobic capacity of soccer players that sustained lower-body injuries during the in-season period compared to those that did not have a lower-body injury. A secondary purpose was to compare the aforementioned parameters between the players that sustained a knee ligament injury and hamstring strain. One hundred and thirty-three division 1 soccer players participated in the study. Fitness testing was conducted at the end of the pre-season period, and the players were followed for a total of 20 games. The anthropometric, lower body strength, flexibility and aerobic capacity parameters were compared between the players that sustained hamstring strains and knee ligament injuries and those that did not sustain any injuries. Results indicated that injured players were significantly older and less flexible than non-injured players (p<0.05). Additionally, injured players appeared significantly weaker on the right and left quadriceps and hamstring muscles (p<0.05). Furthermore, injured players had significantly greater asymmetries for the hamstrings muscle (p<0.05) and significantly lower VO2max values and running time than the non-injured players (p<0.05). Lastly, a significant difference between the players that sustained a hamstring injury compared to those who sustained a knee injury was indicated in right hamstring strength, right side ratio, and hamstring asymmetries (p<0.05). Our findings suggest that off- and pre-season interventions should be tailored toward increasing aerobic fitness and lower body strength and flexibility while minimizing strength asymmetries and imbalances to reduce in-season injury risk.