Changes in human walking dynamics induced by uneven terrain are reduced with ongoing exposure, but a higher variability persists

Jenny A Kent,Nicholas Stergiou,Joel H Sommerfeld

doi:10.1038/s41598-019-54050-z

Jenny A Kent, Nicholas Stergiou + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-54050-z

Copy DOI

Abstract

During walking, uneven terrain alters the action of the ground reaction force from stride to stride. The extent to which such environmental inconsistencies are withstood may be revealed by the regulation of whole-body angular momentum (L) during walking. L quantifies the balance of momenta of the body segments (thigh, trunk, etc.) about their combined center of mass, and remains close to zero during level walking. A failure to constrain L has been linked to falls. The aim of this study was to explore the ability of young adults to orchestrate their movement on uneven terrain, illustrated by the range of L (LR) and its variability (vLR). In eleven male adults, we observed significant increases in sagittal plane LR, and vLR in all three planes of motion during walking on an uneven in comparison to a flat surface. No reductions in these measures were observed within a 12-minute familiarisation period, suggesting that unimpaired adults either are unable to, or do not need to eliminate the effects of uneven terrain. Transverse plane LR, in contrast, was lower on immediate exposure, and then increased, pointing to the development of a less restrictive movement pattern, and would support the latter hypothesis.

Highlights

IntroductionUneven terrain alters the action of the ground reaction force from stride to stride
During walking, uneven terrain alters the action of the ground reaction force from stride to stride
The whole-body angular momentum (L), which can be computed across the gait cycle, represents the sum of all rotational momenta of the segments acting about a set point, e.g. their combined center of mass (COM) (Fig. 1), and provides a quantification of the combined effect of their relative movements[8,9,10]

Summary

Introduction

Uneven terrain alters the action of the ground reaction force from stride to stride. Maintaining balance during walking depends on the ability of the individual to effectively control the center of mass (COM) of the body with respect to the feet[6,7] This occurs through the coordination of rotations of the segments of the body; via muscle action that is appropriately timed given the intrinsic demands of the task[8,9]. L is low in normal walking despite substantial values at segmental level[10,13]; less than 0.05 dimensionless units when normalised to mass, height and velocity To put this into context, Herr & Popovic[10] illustrated this to be as low as one sixth of the angular momentum of analogous point mass rotating rigid body systems[10]. Given that external forces would act to increase forward angular momentum on a decline, this finding implies the use of active control that over-compensates for this change in demand, but reduces the risk of a fall

Objectives

Methods

Results

Discussion

Conclusion