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

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.

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.

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.

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.