The Association Between Leg Skeletal Muscle Mass And Isokinetic Performance Following Anterior Cruciate Ligament Reconstruction

Isokinetic testing is a recognized modality used to quantify recovery following quadriceps autograft anterior cruciate ligament reconstruction (QT-ACLR), but is often not incorporated into routine clinical practice due to cost and time limitations. Bioelectrical impedance is an easily available, reliable way to estimate segmental skeletal muscle mass. It has been shown that a moderate to strong relationship exists between lean muscle mass and isokinetic strength in healthy college athletes using dual-energy x-ray absorptiometry. While it is plausible that skeletal muscle mass has a similar relationship, there is no literature comparing the relationship between leg skeletal muscle mass and isokinetic measures. PURPOSE: This study aimed to provide preliminary data for the association between the difference of skeletal muscle mass and isokinetic performance between legs following QT-ACLR. We hypothesized that differences for leg skeletal muscle mass will be associated with differences that are seen with isokinetic performance. METHODS: 24 patients (M/F: 17/7, Age: 26.7 ± 5.6, Time Since Surgery: 35.1 ± 17.4 weeks) with QT-ACLR were included in the analysis. Bioelectrical impendence using phase-sensitive multifrequency measured fat free mass and skeletal muscle mass of each leg. Isokinetic testing was then conducted for knee extension and flexion at 60, 180, and 300 deg·s-1. Pearson correlation coefficients, and their 95% confidence intervals (CI), were used to determine the association between interlimb differences (operative minus non-operative) in leg skeletal muscle mass (kg expressed as percent of total-body skeletal muscle mass) and isokinetic peak torque (Nm expressed as percent of body mass). RESULTS: Weak to moderate positive correlations were observed between the interlimb difference in leg skeletal muscle mass and isokinetic peak torque at 60 deg·s-1 (r = 0.457, p < .05, CI: 0.066, 0.727), 180 deg·s-1 (r = 0.584, p < .01, CI: 0.237, 0.799 ), and 300 deg·s-1 (r = 0.599, p < .01, CI: 0.259, 0.808 ) post-surgery. CONCLUSION: Preliminary results reveal an association between interlimb differences in leg skeletal muscle mass and isokinetic peak torque at all three speeds (60 deg·s-1, 180 deg·s-1, and 300 deg·s-1). Bioelectrical impedance could provide an alternative to monitor recovery post QT-ACLR.