Paradoxical network rigidity and peripheral decoupling: age-related breakdown of adaptive postural control

Older adults face disproportionate fall risk during dual-task conditions, yet the neuromechanical basis remains elusive. We reveal a mechanistic paradox: aging reorganizes whole-body coordination through globally rigid, hyper-connected networks that paradoxically decouple the peripheral effectors critical for balance. Motion capture analysis (48 younger, 48 older adults; 21 markers) during stance on stable/unstable surfaces with and without cognitive load showed that younger adults dynamically reconfigure coordination architectures, with task-specific modulation of local clustering, global efficiency, and peripheral-to-center-of-mass coupling.

Older adults instead exhibited chronically rigid networks—elevated local transitivity, global efficiency, and small-worldness, hallmarks of ostensibly superior organization—yet showed reduced inter-modular flexibility and, critically, weakened foot–ankle–shank-to-center-of-mass coupling during instability, precisely when distal control becomes essential. This rigidity persisted across mechanical and cognitive challenges and throughout sustained trials, independent of sway magnitude or fatigue, indicating chronic reorganization rather than transient compensation. Age-related motor decline thus reflects not component degradation but qualitative network rigidification: loss of context-sensitive reconfiguration capacity.

These findings establish network flexibility metrics as mechanistic markers for fall risk and reframe intervention targets from component strengthening toward restoring organizational plasticity—the capacity to selectively assemble, dissolve, and reassemble coordination patterns as task demands evolve. We gratefully acknowledge financial support from the National Science Foundation (NSF) EPSCoR Program (Grant No. OIA-2044049) and the Nebraska Collaborative Initiative, both awarded to Madhur Mangalam.

We also acknowledge institutional support from the Center for Research in Human Movement Variability and the Center for Cardiovascular Research in Biomechanics (CRiB) at the University of Nebraska at Omaha, which are funded by the National Institute of General Medical Sciences (NIGMS) of the National Institutes of Health (NIH) under Grant Nos. P30GM159554 and P20GM152301. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NSF or the NIH/NIGMS.

Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE, USA Madhur Mangalam, Brian Schlattmann, Jessica Fabianiak & Theodoros Deligiannis The authors declare no competing interests. Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material.

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