Effects of visual input on contralateral foot touch and postural stability during one-leg standing in older adults...

Compensatory weight transfer is essential for balance control and functional mobility, yet few studies have investigated contralateral touch behavior during one-leg standing, particularly in individuals with chronic low back pain (LBP).

This study evaluated the influence of visual input on postural stability, with specific attention to the initiation and total duration of contralateral foot touches across three repeated trials in adults with LBP.

Twenty-seven participants with LBP and 44 control participants performed 10-second one-leg standing tasks on their non-dominant limb under eyes-open and eyes-closed conditions. Two primary outcomes were assessed across three trials: (1) occurrence of contralateral foot touch within the first second (early stance response), and (2) total duration of foot contact during the entire trial.

Sample size estimation indicated that a minimum of 25 participants per group would yield 80% power to detect a moderate effect size (Cohen's d = 0.4). A significant interaction was observed between visual condition and repetition (F = 7.86, p = 0.01), although no significant group interaction was found for total contralateral touch duration (F = 1.59, p = 0.21). The LBP group exhibited significantly more early contralateral touches during the first trial with visual input (t = 3.46, p = 0.001) and during the third trial without visual input (t = -3.53, p = 0.001), suggesting impaired adaptability to sensory conditions.

Although total contralateral touch duration did not differ significantly between groups, individuals with LBP demonstrated greater instability during the initial phase of one-leg stance. These findings highlight early stance responses as a sensitive marker of balance impairment in LBP and support the need for interventions that enhance somatosensory integration and postural initiation strategies.