Knee Extensor Rate Of Torque Development Assessment Post-acl Reconstruction: Does Sampling Rate Matter?

Abstract

Impaired quadriceps neuromuscular function is a hallmark of anterior cruciate ligament injury and reconstruction (ACLR). Recent investigations suggest that reduced knee extensor rate of torque development (RTD) is strongly associated with abnormal movement mechanics post-ACLR and persists at or beyond return to sport. RTD is typically quantified at high (≥1000 Hz) sampling rates (SR), which is a barrier to clinical assessment as most clinical equipment features low SR (100 Hz). PURPOSE: To determine how SR influences knee extensor RTD in collegiate athletes near return to sport post-ACLR. METHODS: 35 Division I athletes (age 20.6 ± 1.6 y, BMI 25.0 ± 3.3 kg/m2, 21 female) performed rapid maximal effort isometric knee extension contractions at 9.1 ± 2.5 months post-ACLR on an isokinetic dynamometer. Torque signals were sampled at 2000 Hz. RTD was characterized with multiple variables: from contraction onset to 50, 100, and 200 ms (RTD0-50, RTD0-100, and RTD0-200, respectively), in sequence from 50 to 100 ms and 100 to 200 ms (RTD50-100 and RTD100-200), as the slope of 20-80% of peak torque (RTD20-80), and as the maximal instantaneous slope (RTDPeak). Torque signals were then downsampled to 100 Hz and all RTD variables re-calculated. Limb Symmetry Indices (LSI) were computed for all variables at both SR. Bland-Altman analyses, intraclass correlation coefficients (ICC), and root-mean-square errors (RMSE) assessed the agreement between 2000 Hz and 100 Hz RTD variables for both involved limb RTD and between-limb LSIs. RESULTS: Knee extensor RTD0-50, RTD50-100, and RTD0-100 demonstrated the lowest levels of agreement between 100 Hz and 2000 Hz SR. Conversely, RTD0-200, RTD20-80, and RTDPeak had the highest levels of agreement.CONCLUSIONS: Involved limb RTD and RTD LSI for RTD0-200, RTD20-80, and RTDPeak can be accurately assessed with reduced sampling rates, thereby facilitating use of clinically available equipment for assessing knee extensor RTD post-ACLR.