Mechanisms that stabilize human walking

Abstract


 
 
 In this paper we review what mechanisms are used to stabilize human bipedal gait. Based on mechanical reasoning, potential mechanisms to control the body center of mass trajectory are modulation of foot placement, stance leg control consisting of modulation of ankle moments and push-off forces, and modulations of the body’s angular momentum. The first two mechanisms and especially the first are dominant in controlling center of mass accelerations during gait, while angular momentum control plays a lesser role, but may be important to control body alignment and orientation. The same control mechanisms stabilize both steady-state and perturbed gait in both the mediolateral and antero-posterior directions. Control is at least in part active and is affected by proprioceptive, visual and vestibular information. Results support that this reflects a feedback process in which sensory information is used to obtain an estimate of the center of mass state based on which foot placement and ankle moments are modulated. These active feedback mechanisms suggest training approaches for populations at risk of falling, such as augmenting their effective use by means of augmented feedback, or using their complementary nature to train one mechanism by constraining the other mechanisms.
 
 

Editorial: Effects of aging on locomotor patterns

“…For instance, by increasing step width, typically observed in older and PD individuals, the strength of the coupling of the mediolateral CoM state and foot placement may decrease 24 . Additionally, as also mentioned by van Leeuwen et al 23 , sensing and actuation of those mechanisms are strictly relevant to actively controlling stability during gait. As both sensing and actuation are diminished in aging and diseases, these factors combined may partially explain the reduced control of gait stability in those populations.…”

“…Particularly relevant, the present study supports the understanding of the circumstances related to trips and the development of effective interventions to prevent trip-related falls in older individuals 22 . The authors also argued that whether the trip occurs with the leading or trailing limb may be harder to control the center of mass (CoM) and restore stability during walking, which is particularly challenging, as pointed out by van Leeuwen et al 23 and discussed as follow.…”

“…Walking stability requires a complex interaction of several mechanisms 23 that involves a net of functions affected by aging, and even more in AD and PD. Investigating Special issue: Effects of aging on locomotor patterns those mechanisms, van Leeuwen et al 23 proposed an overview of potential mechanisms of gait stability control during unperturbed and perturbed walking. The focus of the review was on detailing three mechanisms of walking stability: (1) foot stability, (2) stance leg control, and (3) angular momentum changes.…”

“…One of the main clinical relevance of understanding the mechanisms and factors linked with whether and how age-and age-related diseases affect walking is centered on developing or optimizing intervention strategies (e.g., prevention and rehabilitation). Not differently, papers composing this special issue suggested 12,22 , or even directly indicated 23 , training strategies for general or specific aspects related to improving walking. Barbieri and colleagues 12 suggested that exercise programs focusing on maintaining body composition (especially with a mechanical load) would reflect in the maintenance of walking speed and stability.…”

“…Those suggestions confirm the cumulative and systematic evidence on exercise effectiveness on walking ability, improving performance, and reducing falls in older and PD individuals 25,26 . Specifically considering intervention focusing on the mechanisms of gait stability, van Leeuwen et al 23 discussed detailed strategies to improve foot placement and stance leg control. The authors suggested that mechanically perturbed gait stability, specifically perturbed or augmented use of stabilizing mechanisms, may be potential training approaches for improving gait stability.…”