The effects of increasing insole stiffness on foot and ankle mechanics in walking gait

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Biomedical Engineering - Applications, Basis and Communications








The energetic pattern of the foot–ankle system is critical in human walking gait. While some of the mechanical energy was dissipated due to foot segment deformation in walking stance phase. Increasing footwear insole bending stiffness was reported to restrict foot segment bending behavior and this was reported to reduce foot segment energy dissipation. While little is known whether increasing footwear insole bending stiffness would alter foot–ankle system mechanical work generation and absorption patterns. Two healthy subjects (one female, one male; age 26.5 ± 6.4 years, height 168.5 ± 2.1 cm, weight 64.9 ± 5.4 kg) participated in this study and they were asked to walk at self-selected normal speed with the same footwear (Nike Free RN Flyknit, 2017) in two different insole stiffness conditions: (i) normal shoe insole (NSI); (ii) carbon fiber insole (CFI). Paired sample t-test was conducted between NSI and CFI for all outcome measures. No statistically significant differences in the outcome variables were found between the two insole conditions. While foot segment positive work and mechanical work ratio were 45.54% and 68.43% higher in CFI than in NSI condition, respectively; foot negative work was 25.02% lower in CFI than in NSI condition. However, ankle joint positive work and work ratio were around more than 10% higher in NSI than in CFI condition, and ankle peak positive power in NSI was 23.93% higher than in CFI condition. Additionally, foot–ankle system overall positive work and mechanical work ratio were both similar between NSI and CFI conditions. The findings indicate increasing footwear insole bending stiffness may influence foot segment and ankle joint energetic patterns in walking stance phase. And the mechanical energy generation compensatory mechanism may exist between foot segment and ankle joint. Specifically, a decreased foot segment energy generation tended to result in a higher amount of ankle joint positive work and peak power generation. This will be beneficial for maintaining a relatively consistent foot–ankle system overall energy generation and work ratio in response to altered insole stiffness and foot segment work during gait.


Foot and ankle, Insole stiffness, Joint stiffness, Mechanical work