How Healthy Older Adults Regulate Lateral Foot Placement While Walking in Laterally Destabilizing Environments
Meghan Kazanski a,b, Joseph P. Cusumano c, Jonathan B. Dingwell a,b,*
b Department of Kinesiology & Health Education, The University of Texas at Austin, Austin, TX 78712 USA
b Department of Kinesiology, The Pennsylvania State University, University Park, PA 16802 USA
c Department of Engineering Science & Mechanics, The Pennsylvania State University, University Park, PA 16802 USA
Gait variability is generally associated with falls, but specific connections remain disputed. To reduce falls, we must first understand how older adults maintain lateral balance while walking, particularly when their stability is challenged. We recently developed computational models of lateral stepping, based on Goal Equivalent Manifolds, that separate effects of step-to-step regulation from variability. These show walking humans seek to strongly maintain step width, but also lateral position on their path. Here, 17 healthy older (ages 60+) and 17 healthy young (ages 18–31) adults walked in a virtual environment with no perturbations and with laterally destabilizing perturbations of either the visual field or treadmill platform. For step-to-step time series of step widths and lateral positions, we computed variability, statistical persistence and how much participants directly corrected deviations at each step. All participants exhibited significantly increased variability, decreased persistence and tighter direct control when perturbed. Simulations from our stepping regulation models indicate people responded to the increased variability imposed by these perturbations by either maintaining or tightening control of both step width and lateral position. Thus, while people strive to maintain lateral balance, they also actively strive to stay on their path. Healthy older participants exhibited slightly increased variability, but no differences from young in stepping regulation and no evidence of greater reliance on visual feedback, even when subjected to substantially destabilizing perturbations. Thus, age alone need not degrade lateral stepping control. This may help explain why directly connecting gait variability to fall risk has proven difficult.
Figure: (A): Young healthy (YH) and older healthy (OH) adults navigated virtual environments in the presence of either no (NOP), visual (VIS) or platform (PLAT) perturbations. (B-D): All participants demonstrated reactive lateral stepping adaptations when perturbed. YH and OH groups did not demonstrate differences in stepping variability (B), statistical persistence of stepping deviations (C), or linear correction of stepping errors (D).
Highlights
Biomechanical variability is ubiquitous during walking, especially in the presence of physical and perceptual perturbations.
Variability, associated with both aging and impaired gait, may be detrimental or beneficial to adapting locomotor adaptations.
Older and younger adults similarly increased reactive stepping variability of foot placement to overcome destabilizing perturbations.
This variability may be structured to purposfully adapt reactive step-to-step regulation of foot placement to destabilizing perturbations.
Aging alone does not degrade reactive stepping variability or neuromechanical regulation amidst perturbations.
This may explain why directly connecting gait variability to age-related falling risk has proven difficult.