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

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.