Postural Sway in Adults and Elderly Individuals During Local Vibratory Stimulation of the Somatosensory System

Abstract

This study aimed to assess the differences in the somatosensory control strategies between healthy adults and elderly individuals during postural tasks. The center of pressure displacement was determined in 30 elderly individuals and 30 adults who were instructed to stand upright with closed eyes on a balance board. Vibratory stimulation at 30 and 240 Hz was applied to the lumbar multifidus and gastrocnemius (GS) muscles bilaterally to evaluate the contributions of these different somatosensory signals to balance control. Compared with the adults, the elderly individuals were significantly more dependent on the GS at 30 (p = 0.002) and 240 Hz (p < 0.001) in their postural control and showed a higher relative somatosensory weighting ratio (RSW) at 240 Hz (p = 0.03). The postural strategy adopted by elderly individuals depended on the somatosensory stimulation of the GS at 30 and 240 Hz, which was increased by RSW at 240 Hz depending on the postural control strategy of the ankle. The elderly individuals in this study showed an ankle strategy in response to the RSW at the Vater-Pacini corpuscle rather than at the muscle spindle level. The Vater-Pacini corpuscle–derived RSW in elderly individuals was the novel finding of this study. RSW assessments using somatosensory stimulation at 240 Hz may provide a useful index to measure the postural stability of elderly individuals.