Can increasing footwear bending stiffness ameliorate age-related mechanical and metabolic deficits in walking?
Abstract
Older adults consume metabolic energy faster than their younger adult counterparts while walking, particularly on sloped terrain. This increased rate is likely in part due to an age-related shift in moment and power production from the ankle joint to the hip. Shifting these mechanics proximally may occur due to older adults losing more mechanical energy at the foot and producing lower ankle joint moments, deficits that are exaggerated when walking uphill or against impeding forces. A promising method to target these foot and ankle mechanics is increasing footwear longitudinal bending stiffness via carbon fiber insoles. We examined how increasing footwear stiffness alters older adult (9F/10M, 70 ± 5.9 yrs) walking energetics across slopes. Increasing footwear stiffness indeed reduced the magnitude of negative power from the distal foot+shoe structures but increased negative power of the foot+shoe system as a whole. At the ankle, peak joint moment increased by ~10% in the stiffest footwear compared with the baseline standardized shoe. Neither knee and hip mechanics nor net metabolic power were consistently affected by footwear stiffness. These results indicate that increasing older adult footwear stiffness via flat carbon fiber insoles helps to address some age-related deficits in foot and ankle mechanics but does not result in a clear attenuation of the age-related distal to proximal shift in joint mechanics. However, stiffer footwear allows older adults to produce greater ankle joint moments without incurring a metabolic penalty, which could have important implications for walking speed, propulsion, fatigue resistance, and balance recovery capacity.