The Effect of Shoe Insole Stiffness Modifications on Walking Performance in Older Adults: A Feasibility Study

Shoes or insoles embedded with carbon fiber materials to increase longitudinal stiffness have been shown to enhance running and walking performance in elite runners, and younger adults, respectively. It is unclear, however, if such stiffness modifications can translate to enhanced mobility in older adults who typically walk with greater metabolic cost of transport compared to younger adults. Here, we sought to test whether adding footwear stiffness via carbon fiber insoles could improve walking outcomes (eg, distance traveled and metabolic cost of transport) in older adults during the 6-minute walk test. 20 older adults (10 M/10 F; 75.95 [6.01] y) performed 6-minute walk tests in 3 different shoe/insole stiffnesses (low, medium, and high) and their own footwear (4 total conditions). We also evaluated participants' toe flexor strength and passive foot compliance to identify subject-specific factors that influence performance from added shoe/insole stiffnesses. We found no significant group differences in distance traveled or net metabolic cost of transport (P ≥ .171). However, weaker toe flexors were associated with greater improvement in distance traveled between the medium and low stiffness conditions (P = .033, r = -.478), indicating that individual foot characteristics may help identify potential candidates for interventions involving footwear stiffness modifications.