Mechanical and cognitive postural challenges drive shifts in whole-body coordination network

Conventional human movement science often considers body parts and processes separately as belonging to complementary but distinct domains (motor control, cognition). We break with this tradition by exploring how mechanical and cognitive demands jointly shape whole-body functional coordination in healthy young adults. Forty-eight participants performed postural control tasks under four conditions: stable surface without cognitive load, stable surface with the Trail Making Test (TMT) Part A, wobble board without TMT and wobble board with TMT. Whole-body coordination networks were derived from motion capture data of 21 retroreflective markers after controlling for the movement of the body's centre of mass. Wobble board-induced mechanical instability shifted the whole-body coordination network from a modular structure to a more integrated and densely connected organization, as indicated by increased local transitivity, local efficiency, degree centrality, global efficiency, global transitivity and small-worldness. This transformation suggests enhanced local cohesion and global connectivity but coincided with reductions in modularity, characteristic path length and participation coefficient, reflecting a loss of distinct community structures and functional specialization. This shift may prioritize rapid global communication over modular control. However, performing TMT with a laser pointer moderated these changes, pulling within-body network relationships towards a less integrated and more specialized state and preserving functional segregation and adaptability. This research transforms our understanding of whole-body coordination by showing how both mechanical and cognitive task constraints alike reshape the structure of whole-body coordination networks, paving the way for breakthroughs in rehabilitation. Long reserved for studying brain function, network analytical methods applied to body movements are poised to bridge the brain-body divide, revealing how locally and globally porous the movement system is to mechanical and cognitive demands.