Attentional focus modulates neuromechanical organization and motor complexity during walking

Attentional focus instructions have long been recognized for their impact on motor performance and learning, yet their influence on the neuromechanical aspects of gait—spanning multiple analytical levels—remains underexplored. In this study, the authors investigated how attentional focus (internal, external, or no focus) and sex affect lower-limb coordination during walking, drawing on a blend of biomechanical and neuromuscular methods. The complexity of kinematic and electromyographic (EMG) signals was quantified using sample entropy, the inter-joint coordination was evaluated through the Uncontrolled Manifold (UCM) framework by calculating the synergy index (ΔV = log₁₀(V_UCM / V_ORT)) in the sagittal, frontal, and transverse planes, and muscle synergies were extracted via non-negative matrix factorization, emphasizing the number needed to account for 90% of the total variance (VAF). The findings highlighted a persistent main effect of attentional focus across all levels. External focus led to greater kinematic and EMG sample entropy, suggesting heightened movement complexity. Likewise, the UCM synergy index (ΔV) was markedly higher with external focus in every plane, indicating more variability that stabilized the task. In muscle synergy analysis, attentional focus reshaped neuromuscular modularity, requiring fewer synergies to achieve 90% VAF under external focus. Sex differences were modest, appearing only in sagittal-plane ΔV, with no interactions between attentional focus and sex. These results illustrate how attentional focus reshapes gait organization from signal complexity to inter-joint coordination and neuromuscular patterns. Together, they bolster the notion that external focus encourages more adaptive, task-oriented control during walking. This underscores the benefits of multilevel analyses in unpacking the mechanisms behind attentional influences on locomotion.