Brain structure–function decoupling and neuromuscular coordination during gait and sit-to-stand in healthy aging

Abstract

Age-related decline in lower-limb motor function reflects complex interactions between central brain networks and peripheral neuromuscular coordination. This study examined how structural–functional brain organization relates to muscle coordination, intermuscular coupling, and biomechanical control during gait and sit-to-stand (STS) tasks. In this exploratory multimodal study, thirteen healthy young adults and sixteen healthy older adults underwent resting-state fMRI, DTI, surface electromyography, motion capture, plantar pressure, and ground reaction force measurements. Muscle synergy similarity, intermuscular coherence (IMC), IMC network efficiency, center-of-pressure (COP), ground reaction force (GRF), and structure–function decoupling index (SDI) were quantified and analyzed. Older adults exhibited lower muscle synergy similarity and reduced gait-related IMC and IMC network efficiency, together with altered COP and GRF patterns. Regional SDI alterations were concentrated in basal ganglia/striatal, cingulate, and insular regions. In age-group-adjusted exploratory analyses, STS muscle synergy similarity and mean IMC showed nominal positive associations with SDI in the right ventromedial putamen and right dorsal area 23; however, these associations did not survive FDR correction across the candidate ROIs. Healthy aging is associated with task-dependent reorganization of lower-limb neuromuscular control and selective basal ganglia-striatal structure–function alterations. These findings provide multimodal evidence of parallel central and peripheral reorganization during healthy aging and identify candidate brain-muscle associations for future longitudinal and confirmatory investigation.