Uniplanar aquatic exercise quantified with inertial sensors and pose estimation

This study presents a concurrent validity analysis of two measurement techniques for quantifying uniplanar human movement during aquatic exercise. Established marker-based biomechanical motion capture systems are labour intensive, and command significant prices, limiting their accessibility in non-specialist environments. Therefore, this study assesses the applicability of alternate measurement methods; inertial measurement unit (IMU) sensors and markerless computer vision (CV) tracking in the form of pose estimation, applied to the quantification and analysis of aquatic exercise. This analysis establishes the validity of each method by deriving several performance-related metrics; range of motion, duration, and angular velocity, of uniplanar aquatic exercise repetitions. Using the proposed methods it was observed that each performance metric demonstrated excellent agreement (ICC ≥ 0.94) across methods, based on intraclass correlation coefficients in 20 healthy young adults (n = 9 women, aged 20-26). This analysis encompassed two exercise types, knee flexion-extension and hip flexion-extension. The authors highlight that this contribution represents a step toward establishing robust, accessible methods for objective exercise quantification in aquatic settings, where previously there has been an absence of convenient technical solutions.