Effects of protruding knob heights in site-specific somatosensory foot orthoses on postural balance in older adults: A dose-response study

Background: The aging process involves many physiological changes that can significantly affect postural balance and stability. This study examines the effects of varying the height of protruding knobs in site-specific stimulating foot orthoses on postural balance and stability in older adults.

Methods: A crossover trial was conducted with 10 older adults aged 65 and above. Participants were randomly assigned to four different foot orthosis conditions with varying protruding knobs heights: flat foot orthosis without knobs, stimulating foot orthosis with short, medium-height, and tall protruding knobs. Postural balance and stability were assessed using standardized balance and stability tests, including center of pressure trajectory, computerized dynamic posturography, and subjective feedback. 

Findings: The current findings revealed that stimulating foot orthosis with tall protruding knobs reduced both anteroposterior and mediolateral center of pressure displacements during standing with eyes open. Additionally, stimulating foot orthosis with tall protruding knobs increased center of pressure maximum velocity during walking on sloped surfaces. In posturography assessments, stimulating foot orthosis with tall and medium-height protruding knobs improved equilibrium scores. Although the differences were not statistically significant, a trend toward decreased comfort was observed with increasing protrusion height.

Interpretation: Height of protruding knobs appears to induce a positive dose-response effect on enhancing postural control in older adults. However, addressing the associated discomfort through design modification is crucial for their practical application. Longitudinal study with larger sample sizes is recommended to confirm optimal dosing strategies for site-specific stimulation.