Effects of somatosensory stimulation foot orthoses on balance and stability in older adults: A systematic review, meta-analysis, and meta-regression

Background: Somatosensory stimulation foot orthoses (SSFO) are recommended to enhance postural balance by stimulating mechanoreceptors. However, the underlying mechanisms by which SSFO with varying protrusion designs influence postural balance remain unclear. Research question: How do SSFO affect postural balance in older adults, and what role do variations in protrusion design play in these effects? Methods: A systematic search was conducted in PubMed, Web of Science, Scopus, CINAHL, and Cochrane Library from inception to December 2024. Eighteen studies with 27 SSFO conditions examining the effects on static and dynamic balance in older adults were included in the meta-analysis. Balance parameters reported in at least 10 SSFO conditions were further analyzed using meta-regression analysis. Results: Pooled analyses indicated that SSFO use reduced center of pressure (CoP) displacement during standing, particularly in studies evaluating immediate effects and using SSFO with specific design features. Meta-regression analysis revealed significant positive correlations between effect sizes for anteroposterior CoP range and SSFO with arch-support structures [Coeff: 0.45, 95 % CI (0.19, 0.72), p = 0.001] or site-specific protrusions [Coeff: 0.32, 95 % CI (0.09, 0.56), p = 0.008]. SSFO also significantly improved Timed Up and Go scores [MD= -1.15, 95 % CI (-1.82, −0.47), p < 0.001], while no significant changes were observed in gait or other functional mobility measures. Significance: These findings underscore the potential of customized SSFO designs to enhance mechanoreceptor stimulation and improve postural balance in older adults. While design-specific SSFO may support improvements in static balance for clinical applications, evidence of benefits on gait and broader functional mobility is still limited.