Deformable foot orthoses redistribute power from the ankle to the distal foot during walking

Recently, carbon fiber plates, or orthoses, have been incorporated into footwear to improve running performance, presumably through improved energy storage and return. However, few studies have explored the energetic effects these orthoses have on the distal foot, have utilized such orthoses in walking, and none have sought to specifically harness metatarsophalangeal joint deformation to store and return energy to the ankle-foot complex. To address these gaps, we developed and tested a deformable carbon fiber foot orthosis aiming to harness foot energetics and quantify the resulting effects on ankle energetics during walking in healthy adults. Eight subjects walked under three conditions: barefoot (BF), with minimalist shoes (SH), and with bilateral, deformable foot orthoses in the minimalist shoes (ORTH). Ankle and distal foot energetics, foot-to-floor and ankle angle, stance time, step length, and max center of pressure (COP) position were calculated. When walking with the orthoses, subjects showed 263.6% increase in positive distal foot work along with a 31.9% decrease in ankle work and little to no change in the overall ankle-foot complex work. Step length, stance time, and max anterior COP position significantly increased with orthosis use. No statistical or visual differences were found between BF and SH conditions indicating that our findings were due to the foot orthoses. These results suggest this foot orthosis redistributes power from the ankle to the distal foot for healthy adults, reducing the energetic demand on the ankle. These results lay the foundation for designing orthotics and footwear to improve ankle-foot energetics for clinical populations.