Contribution of various forefoot areas to push-off peak at different speeds and slopes during walking

Background: Push-off during the terminal stance phase has a major impact on forward progression during walking. During this phase, the ground reaction force is applied to a small area under the forefoot. A better understanding of how single forefoot areas contribute to push-off peak in healthy subjects is needed to develop biomimetic orthopedic devices for forefoot amputees. Research question: What is the contribution of different forefoot sole areas to push-off peak as a function of speed and slope? Methods: In this analytical study, 15 healthy subjects walked on a treadmill at different speeds (0.8 m/s; 1.2 m/s; 1.6 m/s; max. gait speed) without de-/inclination and on different slopes (-10 degrees; -5 degrees; 0 degrees; 5 degrees; 10 degrees) with normal walking speed. The Novel Pedar-X System was used to measure vertical sole force. Push-off peak of the entire sole was determined and relative contributions of the areas under the hallux, first ray, and toes (I-V) were calculated and analyzed using separate repeated-measures ANOVA (alpha = 0.05). Results: Push-off peak increases with faster walking speeds as well as with 10 degrees inclination. Downhill walking is associated with a reduced push-off peak. The contribution of all forefoot areas increases with faster walking speeds and at a declination of -10 degrees. Push-off contribution of the area under the hallux increases by about 64.6% at fast walking compared to slow walking and this increase is higher than that of the area under the first ray and toes (p < 0.05). Significance: These findings indicate the major role of the hallux in speed generation and the importance of the forefoot during downhill walking. The results show the need for an adequate assistive device even in hallux amputation cases to compensate for deficits in the push-off phase.