Effects of a Football Simulated Exercise on Injury Risk Factors for Anterior Cruciate Ligament (ACL) Injury in Amateur Female Players

SIMPLE SUMMARY: Women are more at risk of knee injury affecting the Anterior Cruciate Ligament (ACL) compared to men. However, there is limited literature on risk factors linked to strength in female footballers. The aim of this study was to investigate the effects of fatigue on these risk factors. Thirty-three amateur players (20.3 ± 2.0 years old, 1.67 ± 9.31 m, 63.4 ±8.1 kg, 23.6 ± 5.7% body fat) performed strength assessments of the quadriceps and hamstrings on both legs on an isokinetic dynamometer, before and immediately after a football-specific exercise. Results showed fatigue significantly decreased peak knee flexor strength, the ratio of strength between muscles and the speed at which knee flexor strength is produced (−8.8 to −17.0%) in both legs Furthermore, significant decreases in the ratio of strength between muscles were observed at 10° only in the dominant leg (−15.5%), and at 10°, 20° and 30° in the non-dominant leg (−15.1 to −21.8%). These results suggest a reduced capacity of the hamstrings to stabilise the knee joint with fatigue. Unlike results previously shown on men, the non-dominant leg seemed more affected, highlighting the need to consider specific prevention measures in females. ABSTRACT: Females are more at risk of Anterior Cruciate Ligament (ACL) injuries than males; however, there is limited literature on neuromuscular risk factors such as angle-specific hamstring/quadriceps functional strength ratios (H(ecc)/Q(con)) and rate of torque development (RTD) in female footballers. The aim of this study was to investigate the effects of fatigue on these neuromuscular risk factors. Thirty-three amateur players (20.3 ± 2.0 years old, 1.67 ± 9.31 m, 63.4 ±8.1 kg, 23.6 ± 5.7% body fat) performed strength assessments of the quadriceps (concentrically, Q(con)) and hamstrings (eccentrically, H(ecc)) on both legs on an isokinetic dynamometer, before and immediately after a football-specific exercise. Results showed significantly lower peak H(ecc) (−15.1 to −15.5%), peak H(ecc)/Q(con) (−8.8 to −12.9%) and RTD (−14.0 to −17.0%) for hamstring eccentric contractions after fatigue in the dominant and non-dominant legs. Furthermore, significant decreases in H(ecc)/Q(con) were observed at 10° only in the dominant leg (−15.5%), and at 10°, 20° and 30° in the non-dominant leg (−15.1 to −21.8%). These results suggest a reduced capacity of the hamstrings to stabilise the knee joint with fatigue. Unlike results previously shown on men, the non-dominant leg seemed more affected, highlighting the need to consider specific prevention measures in females.