Relevance of RMS of gait analysis wearable data in evaluating gait asymmetry: a case study

Abstract

High levels of lower-limb functional asymmetry represent a major risk for musculoskeletal injuries in athletes. Its examination can support decision-making of coaches and sports medicine professionals [1]. This case study aims at investigating the feasibility and potentiality of assessing it using RMS values of kinematic, kinetic and EMG data [2]. Within the MOVIDA Project [3], a wearable kit was used, made of load insoles (INS) (Loadsol, novelGmbH, 100 Hz, vertical force at hindfoot, medial and lateral forefoot, and total foot), MIMUs (Opal, APDM, 128 Hz, 2 at the ankles and 1 on the pelvis) and sEMG probes (DueLite, OTBioelettronica, 2048 Hz, lateral gastrocnemius and tibialis anterior). Participants performed the 6MWT on a magnetic treadmill (Power Mag, Toorx). At each minute they were asked for fatigue (6-20 Borg scale) and pain (5-levels Likert scale) perception. Signals were resampled, synchronized, filtered and processed: 20N-threshold (INS); 4th-order Butteworth filter (sEMG: 5-450 Hz; MIMUs: <20 Hz); rectification and enveloping (sEMG); rigid transformation (MIMUs); average removal (sEMG, MIMUs). RMS was calculated for each cycle, segmented on the basis of total force, and normalized to its maximum (INS, MIMUs) or to a modified MVC test (sEMG) (Matlab v2018b). Right and left RMSs were compared for each signal and minute (Wilcoxon independent tests, p<0.05). A professional runner (F, 25 yrs, BMI 21.9), with previous (2020) stress-related micro-fracture at both navicular bones and unresolved right plantar fasciitis, performed a 6MWT maintaining a self-selected speed in the range 1.3-1.7 m/s, walking 540 m. Perceived fatigue and pain (right foot) ranged 12-14 and 2-3 respectively. Left-right RMSs were significantly different for all signals and minutes, with the exception for ant-post acceleration. Angular velocity in the frontal plane, had much higher RMS on the left, decreasing during the test from 27 to 25%. Lateral foot was about 10% more loaded on the right while all other force RMSs were significantly higher on the left (Fig. 1). Normalized RMS seems a valuable metric to analyze and interpret signals from wearables. It reveals kinematic, kinetic and EMG variables mostly affected by gait asymmetries. In the case-study, heel pain caused a 27% reduction of frontal plane foot motion, with a 10% less effective foot-ground interaction.