Limb dominance influences rambling but not trembling or entropy during static single-leg stance.

OBJECTIVE: The purpose of this study was to investigate limb differences in the components or structure of postural sway during static single-leg stance using rambling and trembling analysis and the sample entropy measure. METHODS: Twenty healthy young subjects stood still on each foot for 35 s on a force plate. The displacements of the center of pressure (COP) was decomposed into rambling and trembling components in the anterior-posterior (AP) and medial-lateral (ML) directions. The 95% confidence ellipse area, root mean square (RMS), mean velocity, and sample entropy (SampEn) of the COP, rambling, and trembling were analyzed. RESULTS: The results showed significantly greater RMS (Bonferroni corrected p = 0.038, Cohen's d= 0.84) in the COP displacement in the ML direction when standing on the non-dominant leg (95% CI 0.65 cm, 0.80 cm) than the dominant leg (95% CI 0.75 cm, 0.90 cm). There was also a significant RMS difference (Bonferroni corrected p = 0.030, Cohen's d= 0.86) in the rambling component between the dominant (95% CI 0.49 cm, 0.63 cm) and non-dominant (95% CI 0.59 cm, 0.74 cm) legs in the ML direction. However, there were no significant differences in the mean velocity and SampEn of the COP, rambling, and trembling displacements. CONCLUSION: The increases in the rambling component may indicate a greater reliance on supraspinal processes, reflecting an adaptive control in the face of reduced automaticity in the non-dominant leg. The results suggest that postural control during single-leg stance was partially influenced by limb dominance.