A neuromechanical framework for the development of interlimb coordination

Interlimb coordination is a defining property of human locomotion that emerges from the interplay of spinal pattern generation, sensory feedback, and supraspinal modulation across development. Evidence from neonatal, and infant studies shows that left-right and arm-leg couplings are present at birth yet remain highly flexible: neonatal circuits can express alternating or synchronous patterns depending on sensory context, and their coupling strength changes with loading or mechanical constraints. Over the first two years, coordination becomes more reliable and task-specific as supraspinal pathways, intraspinal circuits, and multisensory integration mature in parallel with growth-related biomechanical changes. These processes are accompanied by reductions in variability and stabilization of phase relations. Synthesising humans and non-human animals' evidence, we argue that interlimb coordination should be understood as a multilevel, calibrating system. We further show how neuromechanical models that integrate different levels of control, together with developmental parameterisation, offer principled tests of otherwise intractable hypotheses. Finally, we outline translational opportunities in paediatrics, where conserved arm-leg interactions and model-informed interventions may help identify atypical developmental trajectories and guide early rehabilitation.