Effects of shoe sole geometry on toe clearance and walking stability in older adults

Thirty-five percent of people above age 65 fall each year, and half of their falls are associated with tripping: tripping, an apparently 'mundane' everyday problem, therefore, significantly impacts on older people's health and associated medical costs. To avoid tripping and subsequent falling, sufficient toe clearance during the swing phase is crucial. We previously found that a rocker-shaped shoe sole enhances toe clearance in young adults, thereby decreasing their trip-risk. This study investigates whether such sole design also enhances older adults' toe clearance, without inadvertently affecting their walking stability. Toe clearance and its variability are reported together with measures of walking stability for twelve older adults, walking in shoes with rocker angles of 10°, 15°, and 20°. Surface inclinations (flat, incline, decline) were chosen to reflect a potential real-world environment. Toe clearance increased substantially from the 10° to the 15° rocker angle (p=0.003) without compromising measures of walking stability (p>0.05). A further increase in rocker angle to 20° resulted in less substantial enhancement of toe clearance and came at the cost of a decrease in gait speed on the decline. The novelty of this investigation lies in the exploration of the trade-off between reduction of trip-risk through footwear design and adverse effects on walking stability on real-life relevant surfaces. Our two studies suggest that the current focus on slip-resistance in footwear design may need to be generalised to include other factors that affect trip-risk.