Step-by-step variability of swing phase trajectory area during steady state walking at a range of speeds

Abstract

BackgroundStep kinematic variability has been characterized during gait using spatial and temporal kinematic characteristics. However, people can adopt different trajectory paths both between individuals and even within individuals at different speeds. Single point measures such as minimum toe clearance (MTC) and step length (SL) do not necessarily account for the multiple paths that the foot may take during the swing phase to reach the same foot fall endpoint. The purpose of this study was to test a step-by-step foot trajectory area (SBS-FTA) variability measure that is able to characterize sagittal plane foot trajectories of varying areas, and compare this measure against MTC and SL variability at different speeds. We hypothesize that the SBS-FTA variability would demonstrate increased variability with speed. Second, we hypothesize that SBS-FTA would have a stronger curvilinear fit compared with the CV and SD of SL and MTC. Third, we hypothesize SBS-FTA would be more responsive to change in the foot trajectory at a given speed compared to SL and MTC. Fourth, SBS-FTA variability would not strongly co-vary with SL and MTC variability measures since it represents a different construct related to foot trajectory area variability.MethodsWe studied 15 nonimpaired individuals during walking at progressively faster speeds. We calculated SL, MTC, and SBS-FTA area.ResultsSBS-FTA variability increased with speed, had a stronger curvilinear fit compared with the CV and SD of SL and MTC, was more responsive at a given speed, and did not strongly co-vary with SL and MTC variability measures.ConclusionSBS foot trajectory area variability was sensitive to change with faster speeds, captured a relationship that the majority of the other measures did not demonstrate, and did not co-vary strongly with other measures that are also components of the trajectory.

Fore-aft resistance applied at the center of mass using a novel robotic interface proportionately increases propulsive force generation in healthy nonimpaired individuals walking at a constant speed

“…In this study, we only explored walking function against FA resistance at one constant speed (1.0 m/s). However, prior published research from our lab has explored effects of FA resistance at different speeds, albeit in different experimental conditions, in both healthy-nonimpaired and poststroke populations [11, 31, 34, 35]. We also did not assess a true “no-load” condition (i.e., 0% FA resistance) due to the minimum resistance requirements of the self-driven treadmill’s force-velocity relationship.…”

“…We have previously published detailed descriptions of the control mechanics, walking biomechanics, and energetics in this device in both healthy-nonimpaired individuals and individuals poststroke [31–35]. Briefly, this interface consists of a pelvic mechanism with a pelvic harness that secures participants walking inside it through adjustable cloth straps around the waist and hips.…”

“…Markers were placed bilaterally as follows: acromion processes, manubrium of sternum, thoracic spine level with sternum, ASIS, PSIS, sacrum, midline and lateral thighs, midline and lateral shanks, lateral malleoli, first and fifth digits, and calcaneus (see example marker set-up in Fig. 1) [35]. We collected the real-time velocity of each treadmill belt and forces applied to the pelvic-mechanism force transducers (100 Hz) using our treadmill-interface’s custom software.…”

A Scoping Review on Minimum Foot Clearance: An Exploration of Level-Ground Clearance in Individuals with Abnormal Gait

“…Fourteen out of 43 studies instructed participants to walk at a pre-selected gait speed instead of their preferred speed. Increasing gait speed beyond one’s preferred speed leads to higher MTC with a longer step length [ 26 , 38 , 40 ]. On the other hand, instructing participants to each walk at their preferred gait speed can be problematic.…”

“…The difference in preferred walking speeds among subjects may influence MFC if large enough [ 46 ]. Indeed, higher gait speeds lead to increased MFC [ 26 , 38 , 40 ]. Note that some differences such as stride length and frequency can only be observed at higher gait speeds [ 8 ].…”