Sex Differences in Quadriceps Rate of Torque Development Within 1 year of ACL Reconstruction

Objectives: To investigate the effect of sex on measures of quadriceps strength, rate of torque development, and knee function during the first year following ACLR.

Design: Cross-sectional; SETTING: University community; PARTICIPANTS: Sixty individuals (29 men) with unilateral ACLR in the last 12 months.

Main Outcome Measures: Participants completed bilateral knee extension maximal voluntary isometric contraction (MVIC, Nm/kg) strength assessments. Rates of torque development (Nm*kg*s) were assessed from contraction initiation to 100 ms (RTD) and from 100 ms to 200 ms after contraction initiation (RTD). The effects of sex MVIC strength, RTD, and limb symmetry were assessed using separate ANCOVAs.

Results: Women displayed weaker involved limb (Men = 2.72 ± 0.72 Nm*kg, Women = 2.01 ± 0.50 Nm*kg, p < 0.001) and contralateral limb (Men = 3.15 ± 0.52 Nm*kg, Women = 2.66 ± 0.58 Nm*kg, p < 0.001) MVIC, and slower involved limb RTD (Men = 8.36 ± 3.16 Nm*kg*s, Women = 6.50 ± 2.41 Nm*kg*s, p = 0.01) and RTD (Men = 9.49 ± 3.45 Nm*kg*s, Women = 9.49 ± 3.45 Nm*kg*s, p < 0.001) when compared to men.

Conclusions: Within the first year after ACLR, women displayed bilateral quadriceps weakness and slower involved limb quadriceps RTD when compared to men. Specific focus on facilitating quadriceps hypertrophy and improving neural drive to the quadriceps is indicated when treating female patients attempting to make a return to sport after ACLR.