Reliability Of Inertial Sensor Derived Knee Joint Angular Velocity During A Forward Lunge

Abstract

Incorporating inertial measurement units (IMU) into screening tools affords the ability to ‘quantify’ commonly used functional tasks using angular velocity and acceleration as an outcome variable. These ‘quantified’ tasks have may have greater depth, accuracy and sensitivity than that achieved with standard clinical evaluation tools. Angular velocity can quantify how fast a segment or joint rotates, and provide a preliminary understanding of neuromuscular control during dynamic tasks including a forward lunge. PURPOSE: To determine the reliability of IMU-derived knee joint angular velocity during a forward lunge. METHODS: Twenty-three healthy individuals participated in this study (12M/11F, 30.8 ±8.6years, 1.7 ±0.9cm, 65.3±10.8kg). Participants performed a set of 5 lunges on the right limb and 5 on the left limb, repeated 3 times separated by 10 minute rest periods. Lunge distance was normalized to 100% (±5%) of leg length. IMUs were worn on the lateral thigh and shank of each limb. The following anchor points were defined for segmentation: initiation, initial contact 1 (IC1), midpoint and initial contact 2 (IC2)/termination. Peak and average thigh and shank angular velocity were extracted from the z-axis gyroscope signal for each lunge segment and for a 50ms window either side of IC1. Peak and average knee joint angular velocity in each segment was calculated from thigh and shank data. Intraclass correlation coefficients (ICCs) were calculated based on a mean rating (k=3), absolute agreement, 2-way mixed-effects model. Intra-session reliability was defined as poor (ICC<0.5), moderate (0.5-0.75), good (0.75-0.9) or excellent (>0.9). RESULTS: ICC values ranged from 0.841 to 0.911 for peak left knee joint angular velocity and 0.760 to 0.939 for peak right knee joint angular velocity. Average left knee joint velocity had ICCs raging from 0.912 to 0.972, and 0.922 to 0.965 for average right knee joint angular velocity. CONCLUSIONS: IMU-derived knee joint angular velocity had good to excellent intra-session reliability during a forward lunge and demonstrate good potential for providing objective quantified data on forward lunge performance. IMUs may provide a more accessible alternative to 3D motion analysis or screening tools for lower limb function and neuromuscular control in a clinical setting.