Evaluating Sex Differences In Quadriceps Muscle Fatiguability After Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament tears are among the most frequently occurring injuries in female athletes and are commonly treated by reconstruction surgery (ACLR). Females have reported greater fatigue resistance compared to males, but it remains unclear how sex relates to fatigue post-ACLR. PURPOSE: To evaluate the relationship between sex and quadriceps fatigue post-ACLR. METHODS: Quadriceps strength was tested in 492 subjects between 4-8 months post primary, uncomplicated ACLR (Sex: 256F, 231 M; Age: 23.1 ± 10.3 yrs.; Height; 177.2 ± 10.1 cm; Mass: 75.9 ± 17.9 kg; Time post ACLR: 6.2 ± 1.0 mo). Strength was measured on the involved and uninvolved limbs using an isokinetic dynamometer. Participants were positioned with their knees positioned at 90° of flexion and completed a maximal voluntary isometric contraction (MVIC) of the quadriceps by extending against the stationary dynamometer arm for 30 seconds. An independent samples t-test was used to evaluate the relationship between male and female fatigue rates. A paired samples t-test was used for evaluating fatigue differences between the involved and uninvolved limbs. RESULTS: There were no sex differences in fatigue index between involved limb (p = 0.91) or uninvolved limb (p = 0.99). When eliminating sex as a factor, the involved limb had a lower mean compared to uninvolved (p < 0.001) (Table 1). CONCLUSIONS: Males and females did not exhibit different rates of fatigue during isometric knee extension of the involved limbs. Despite lack of sex differences, the involved/ACLR limb demonstrated significantly less fatigue than the contralateral/involved limb. Table 1: - Means and standard deviations of fatigue. * = statistically significant (p < .05) Group Fatigue (Inv) Fatigue (Un) p-value Female 17.4 ± 11.5 25.1 ± 10.9 .91 Male 16.0 ± 11.7 22.1 ± 10.6 .99 Total 16.7 ± 11.6* 23.7 ± 10.8* .001*