Effect of Extended Relative Phase on Velocity-Based Training Assessment

Velocity-based training can be used for other valuable purposes, such as providing instantaneous feedback to the athletes to promote performance improvements. Although this training tool appears to have many practical functionalities, coaches should not get distracted by the technology and forget what they are actually there to do, which is to coach. This study aimed to propose an extended relative phase (ERP) algorithm for assessing velocity-based training through human pose estimation (HPE) and verifying its feasibility while demonstrating the difference between experts and novices. The coordinating relationship between the trunk and lower limbs during the back barbell squat in this study could be illustrated as a circle. ERP had two leading indices for time series; a Relative phase angle (RP<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Angle</inf>) defined the collaboration between angular displacements and velocities for each joint, and a Relative phase distance (RP<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Distance</inf>) was added to illustrate the stability during the exercise. Through experiments of the back barbell squat with 15kg, a periodicity and amplitude for two time series of RP<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Angle</inf> and RP<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Distance</inf> enabled us to quickly understand the difference in exercise pose between experts and novices. It was concluded that the proposed method allowed coaches to simultaneously assess the angle and angular velocity during the training through ERP despite any particular technical knowledge.