Task-Dependent Bilateral Motor Asymmetries: Evidence for Hierarchical Control in Explosive, Precision, and Complex Motor Skills

Background: Bilateral motor asymmetries reflect the hierarchical organization of neuromotor control, where task complexity differentially engages cortical and subcortical systems. Understanding these asymmetries has implications for motor learning, rehabilitation, and performance optimization. Objective: To examine bilateral lower extremity asymmetries across three levels of hierarchical motor control: explosive force generation (automatic control), precision tasks (moderate cognitive control), and complex motor skills (maximal cognitive control). Methods: In this cross-sectional observational study, 107 healthy adults (51 males, 56 females; age 21.2±2.1 years) completed three motor tasks. Explosive force was assessed via single-leg drop jumps, measuring peak ground reaction force and jump height (n=55). Precision control was evaluated through ball-kicking accuracy (n=52). Complex motor skills were assessed via ball-dribbling speed through a standardized course (n=52). Leg dominance was determined using validated protocols, and task order was randomized. Results: Explosive force tasks demonstrated no significant bilateral differences in peak ground reaction force (dominant: 19.95±4.49 N/kg vs. non-dominant: 20.08±3.88 N/kg, p>0.05) or jump height (17.94±6.89 cm vs. 16.46±10.12 cm, p>0.05). Precision tasks revealed significant asymmetries favoring the dominant leg in kicking accuracy (3.12±2.25 vs. 1.83±1.67 points, p<0.001). Complex motor skills showed superior dominant leg performance in dribbling speed (26.68±6.61 vs. 29.91±6.89 seconds, p<0.001). Conclusions: These findings are consistent with predictions of hierarchical neuromotor control theory, though interpretation is limited by a non-identical participant group, demonstrating task-dependent bilateral asymmetries that trend toward greater asymmetry in tasks with higher cognitive motor demands. Results suggest symmetrical subcortical control for explosive tasks but pronounced cortical lateralization for precision and complex skills, with implications for targeted motor training and rehabilitation strategies.