Functional differences between lower limbs during gait in relation to fall risk.

Introduction: The scientific literature suggests a functional asymmetry between the lower limbs during gait, with the non-dominant limb serving a stabilizing role and the dominant limb a leading role. However, it remains unclear whether this asymmetry is also reflected in local dynamic stability, which has been shown to be significantly related to fall risk. This study aimed to assess differences in local dynamic stability between the dominant and non-dominant limbs in relation to fall occurrence. Methods: The study sample consisted of 131 elderly participants (108 females and 23 males; mean age = 71.0 ± 6.8 years). Local dynamic stability was evaluated using accelerometers attached to the shanks. Outcome variables included short-term and long-term Lyapunov exponents (LE) calculated independently for the vertical, medial-lateral, and anterior-posterior directions. Fall occurrence was prospectively recorded over a one-year period through biweekly phone interviews. After one year, participants were divided into two groups: fallers (at least one fall) and non-fallers (no fall). Results: Significant asymmetries between the dominant and non-dominant limbs were observed in several local dynamic stability parameters. In particular, the non-dominant limb demonstrated better stability in the medial-lateral direction, whereas the dominant limb showed lower LE values in the anterior-posterior direction. No significant main effect of group was observed. However, a significant limb × group interaction was found for long-term LE in the medial-lateral direction, suggesting altered asymmetry patterns in fallers compared to non-fallers. Discussion: In conclusion, this study confirmed the existence of functional asymmetry between limbs during gait in measures of local dynamic stability. The findings suggest that the roles of the limbs are not associated with acute responses but rather with long-term adaptations to perturbations.