Accurate measurement of human movement and joint angles is essential in clinical and research settings. Optical motion capture (OMC) systems are considered the gold standard for these measurements, however, they are expensive, complex, and require highly trained staff to operate. This study evaluated the validity of Moveo Explorers proprietary joint angle approximation algorithm by comparing lower extremity joint angle approximations from wearable inertial measurement units (IMU) with joint angle approximations from OMC systems during walking gait in healthy adults. 

Data were collected from 19 healthy individuals aged 18-30. Participants were instrumented with IMUs (Opal V2; APDM) and reflective motion capture (Qualysis, Motion Analysis) markers from their waist to their feet and completed a 5 minute treadmill walking trial at their preferred speed. Data from both systems were collected simultaneously. 

Validity of wearable IMU joint angle approximations was assessed using intraclass correlation coefficients (ICCs) for each body side (left, right) and joint (hip, knee, ankle) with 95% confidence intervals. ICCs for the right and left hip were 0.995(0.966-0.999) and 0.985(0.735-0.998) and the right and left knee were 0.97(0.795-0.996) and 0.96(0.733-0.994), respectively, indicating excellent agreement. The right and left ankle ICCs were 0.845(0.175-0.978) and 0.856(0.134-0.979), indicating good agreement. 

These findings support the validity of Moveo Explorers proprietary algorithm for lower extremity joint angles during gait in healthy adults, suggesting this wearable IMU system is a practical alternative to OMC. Improved accessibility to accurate, portable motion analysis systems may enhance clinical decision making and support individualized rehabilitation interventions across different settings.