Hamstring To Quadriceps Ratio After ACL Reconstruction In Males And Females

Abstract

PURPOSE: Restoring thigh muscle strength is a universal rehabilitation goal after ACL reconstruction (ACLR). The hamstring to quadriceps (H/Q) ratio has been used both clinically and in the laboratory as an important metric to detect knee strength imbalances. Previous research has identified sex differences in H/Q ratio among young healthy male and female athletes where males exhibit H/Q ratio around 48% and females around 55% at 180°/sec. The purpose was to compare interlimb H/Q ratio in participants with ACL reconstruction (ACLR) and to explore the influence of participants sex. METHODS: Participants with primary, unilateral ACLR were included in the study. Participants with reinjury or revision surgery or bilateral injury were excluded. Data from 318 (155 males, 163 females) participants was recorded (22.4±9.2yr , 1.72±9.8 m, 75.8±18. 1kg, 8.9±7.8 months post-ACLR). We measured isokinetic peak torque at 90°/sec and 180°/sec for the quadriceps and hamstring muscles bilaterally. H/Q ratio was calculated from peak torque. Repeated measures AVOVA was used to compare H/Q between limbs (within-subject) and between sexes (side*sex interaction). RESULTS: We observed a significant main effect for side at 90°/sec (P <0.001) and 180°/sec (P <0.001) indicating the differences among ACLR side and contralateral side (Table 1) such that ACLR side had higher H/Q ratio compared to the contralateral side with medium effect size. Statistically significant differences in H/Q ratio were found among males and females such that females had higher ratio than males at 180°. No significant side* sex effects were found at 90°/sec (P=0.226) and 180°/sec (P=0.383). CONCLUSION: Sex differences in H/Q ratio in the current study are similar to prior reports. We observed higher H/Q ratio on the ACLR sides compared to the contralateral sides at both velocities. Differences in the H/Q ratio persist among ACLR side and the contralateral side following ACLR and this finding is not influenced by sex.Table 1: Within and between subject differences