Motion analysis on backward walking : kinetics, kinematics, and electromyography

Abstract

Backward walking (BW) is a recently emerging exercise. Researches in human walking have classified BW as a reversible movement. Researchers have asserted that joint motions of forward walking (FW) at the hip and ankle are similar to the time-reversed counterpart of BW. However, there has been a lack of research on the kinematic and kinetic aspects of BW relative to research on FW. Though some kinematic analyses of BW have been made, the lack of research on BW lies prominently in its kinetic analysis. Hence, this study has adopted the atypical design: it analyzed the kinetics of BW. Thus the present paper identified the mechanism of BW through kinetic analysis, especially on BW’s time-reversed data and electromyography data. Thirty-one healthy subjects participated in this study. A six-camera 3D motion analysis system was used to acquire three-dimensional data of joint movements during walking. Surface EMG was used to collect the raw EMG data using a Trigno wireless system. Ground reaction force (GRF) curves were acquired from four piezoelectric force plates camouflaged within a 5-m walkway. Each subject performed ten FW trials and forty BW trials with bare feet. For both type of trials, stride characteristics, marker coordinates, electromyography data, and GRFs were recorded simultaneously. Data pairs acquired from the markers and force plates were used to calculate joint angles, moments, and powers through the Plug-In-Gait Biomechanical Modeler pipeline. To follow the purpose of this study, which is to compare the kinematic and kinetic patterns of FW and BW, curves of BW’s joint angles and joint moments were time-reversed to equalize the contact position as well as the type of event. Twenty-six gait parameters generated, twenty-two were analyzed using a paired t-test (p<0.05). The angular and moment patterns of time-reversed BW and FW were statistically significant. The data of EMG and joint powers is also used to analyze the muscle activation during BW, however, this showed great differences with previous studies. This study identified the gait mechanism of BW, and successful results in current and future research in the kinetic and kinematic data of BW will establish a fundamental mechanism of BW.