Neuromechanical response of the upper body to unexpected perturbations during gait initiation in young and older adults

Abstract

Background: Control of upper body motion deteriorates with ageing leading to impaired ability to preserve balance during gait, but little is known on the contribution of the upper body to preserve balance in response to unexpected perturbations during locomotor transitions, such as gait initiation.Aim: To investigate differences between young and older adults in the ability to modify the trunk kinematics and muscle activity following unexpected waist lateral perturbations during gait initiation.Methods: Ten young (25±2yrs) and ten older adults (73±5yrs) initiated locomotion from stance while a lateral pull was randomly applied to the pelvis. Two force plates were used to define the feet centreof-pressure displacement. Angular displacement of the trunk in the frontal plane was obtained through motion analysis. Surface electromyography of cervical and thoracic erector spinae muscles was recorded bilaterally.Results: A lower trunk lateral bending towards the stance leg side in the preparatory phase of gait initiation was observed in older participants following perturbation. Right thoracic muscle activity was increased in response to the perturbation during the initial phase of gait initiation in young (+68%) but not in older participants (+7%). Conclusions:The age-related reduction in trunk movement could indicate a more rigid behaviour of the upper body employed by older compared to young individuals in response to unexpected perturbations preceding the initiation of stepping. Older adults' delayed activation of thoracic muscles could suggest impaired reactive mechanisms that may potentially lead to fall in the early stages of the gait initiation.

A Novel Viewpoint on the Anticipatory Postural Adjustments During Gait Initiation

“…Instead, Maslivec et al ( 2018 ) reported a bilateral excitation in sternocleidomastoid and ES muscles (at T9 and L3 level), again after the backward CoP shift, with a larger delay in sternocleidomastoid in older subjects. The bilateral activation of cervical and thoracic ES in elder subjects is appreciable also in the study by Rum et al ( 2021 ), again about 200 ms after the CoP shift. Wang et al ( 2005 , 2006 , 2017 ) dedicated several studies to this topic.…”

“…So far, only a few studies have searched for activities in trunk muscles linked to gait initiation. Despite the recordings reported in some of those studies (Assaiante et al, 2000 ; Wang et al, 2005 , 2017 ; Ceccato et al, 2009 ; Rum et al, 2021 ) encompassed the initial backward shift of CoP, no description was provided for EMG activities preceding such shift, while changes occurring between CoP shift and heel-off were systematically reported. Assaiante et al ( 2000 ) studied the development of postural chains in children, showing an excitation occurring in both extensor and flexor muscles of the trunk, only on the swing side, about 200 ms before heel-off, i.e., 300 ms after the CoP shift.…”

Measuring Kinematic Response to Perturbed Locomotion in Young Adults

“…Based on the tested population, perturbations of different natures have been used, ranging from cognitive [10] to visual [11] and physical [12]. At the same time, several variables have been considered as sensitive for the quantification of human responses to gait perturbation; among other, spatio-temporal parameters [13], dynamic stability [13][14][15][16], muscular activity [12,17,18], kinematics [14,16,18], and inter-joint coordination [3,19] have been the most adopted ones.…”

“…Moving to kinematics, the analysis of trunk and upper body segments was deeply conducted in previous studies. As an example, Rum and colleagues [18] quantified the trunk kinematic differences between young and older healthy adults following unexpected waist lateral perturbation during walking. A reduction in trunk movement was found as a significant effect of the aging, underlying a more rigid behavior of the upper body in older adults when they are asked to respond to unexpected perturbation.…”

Systematic review of candidate prognostic factors for falling in older adults identified from motion analysis of challenging walking tasks

“…Most perturbations were applied through a translation of the support surface (14 studies), either in the mediolateral or anteroposterior direction, or both. The other types of perturbations were waist-pulls [ 43 , 67 ], ankle pull [ 9 , 50 ], tripping [ 63 ], visual perturbations [ 40 , 75 ], soapy water [ 44 ] and surface drop [ 37 ].…”