Document Type
Article
Publication Date
2026
DOI
10.3389/fnhum.2026.1710840
Publication Title
Frontiers in Human Neuroscience
Volume
20
Pages
1710840
Abstract
Introduction: Age-related declines in walking efficiency are often attributed to musculoskeletal and neuromuscular changes, yet the mechanisms underlying these inefficiencies remain poorly understood. One key contributor is the step-to-step transition (STST), during which the center of mass (CoM) is redirected between limbs. The Sequence (S) index quantifies the temporal overlap between push-off and collision forces during STST, with higher values indicating greater mechanical energy loss. This study investigated whether aging affects STST efficiency, as quantified by the S index, and examined the timing and impulse characteristics underlying observed differences.
Methods: Thirteen young and eleven older healthy adults walked at five speeds relative to their preferred walking speed on an instrumented treadmill while ground reaction force data were collected.
Results: Older adults exhibited significantly higher S index values across all speeds, indicating less efficient gait. These differences were accompanied by shorter pre-HC duration, lower total push-off impulse, lower single support push-off impulse, and higher double support collision impulse. Both groups showed reductions in S index at higher speeds, primarily through increased single-support timing and impulses, and decreased double-support overlap, but older adults remained less efficient overall.
Discussion: These results suggest that aging impairs the temporal and mechanical coordination of STST. This effect may potentially be due to neuromuscular changes. The S index offers a step-level, mechanically grounded metric for assessing gait efficiency and may provide insight into energetic cost in older populations.
Rights
© 2026 Alijanpour, Kulkarni, Adamczyk and Russell.
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Data Availability
Article states: "The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author."
ORCID
0000-0002-9751-7094 (Alijanpour), 0000-0002-9578-1828 (Kulkarni), 0000-0001-9130-1172 (Russell)
Original Publication Citation
Alijanpour, E., Kulkarni, A., Adamczyk, P. G., & Russell, D. M. (2026). The Sequence (S) index as a marker of diminished step-to-step transition efficiency in older adults. Frontiers in Human Neuroscience, 20, Article 1710840. https://doi.org/10.3389/fnhum.2026.1710840
Repository Citation
Alijanpour, Elham; Kulkarni, Ashwini; Adamczyk, Peter G.; and Russell, Daniel M., "The Sequence (S) Index as a Marker of Diminished Step-to-Step Transition Efficiency in Older Adults" (2026). Rehabilitation Sciences Faculty Publications. 173.
https://digitalcommons.odu.edu/pt_pubs/173
Supplementary Material