Single-Leg Balance: Bias for the Non-Preferred Leg in Complex Tasks, But no Association with Footedness

In unchallenging single-leg balance (SLB) tasks, the lower limbs demonstrate symmetrical control and stability. Balance asymmetries between the legs are expected to increase with task demands, being evident in complex motor tasks. In this study, we tested two hypotheses: (1) whether task complexity increases asymmetries in a single-leg balance task, and (2) whether general and specific foot preferences are correlated with performance asymmetries. Twenty-seven right-footed young adults participated by performing two tasks: (1) SLB on a stable surface (SB); and (2) SLB on an unstable surface in the anteroposterior axis (UB). Stability was provided by placing the pressure plate on the floor or on an unstable platform with a hemi-cylinder-shaped support base. Balance performance measurements were obtained through center of pressure displacement and area. Task complexity affected asymmetry direction, showing better performance with the left leg in the UB. The magnitude of asymmetries did not increase between tasks. No correlations were found between preference and performance, with preference matching the side of better performance in only ≅ 50% of the participants. These findings show that more complex motor tasks are necessary for the potential advantages of hemispheric specificity related to motor control balance mechanisms to be manifested.