Shoe Sole with Local Rigidity for Forefoot Running Stability
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Solution Overview
Problem
Existing shoe soles designed for natural forefoot running often hinder the motion by urging an elevation of the heel after ground contact, making it difficult for beginners to sustain a forefoot running style.
Innovation Solution
A sole design that maintains a stable posture with two points of ground contact, ensuring the heel remains in a heel-up state and the sole compressive rigidity is lower at the heel region than at the metatarsophalangeal joints, allowing for natural forefoot movement without hindrance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the sole is designed to support the heel during sinking, then the heel stability is improved, but the forefoot running motion is hindered by urging heel elevation
Solution Approach 1:
The sole is designed with different compressive rigidities at different regions: the heel region has lower compressive rigidity to allow natural sinking and avoid urging heel elevation, while the metatarsophalangeal joints region has higher compressive rigidity to provide support during forefoot running. This local differentiation resolves the contradiction by allowing the heel to remain stable without actively supporting it, thus not hindering the forefoot running motion.
2Strength
If the sole compressive rigidity is increased at the heel region, then the heel support is improved, but the natural forefoot movement is restricted
Solution Approach 1:
The sole implements local quality differentiation by setting the compressive rigidity at the heel region lower than at the metatarsophalangeal joints region. This allows the heel to sink naturally during forefoot running without excessive support, while providing adequate support at the forefoot region, thus resolving the contradiction between heel support and natural forefoot movement.
Solution Approach 2:
The sole design allows dynamic adaptation during the running cycle: during the stance phase, the heel region naturally sinks due to lower rigidity, accommodating the dynamic motion of forefoot running. The higher rigidity at the metatarsophalangeal joints provides necessary support during push-off. This dynamic behavior resolves the contradiction between static heel support and dynamic forefoot movement.
3Stability of the object's composition
If the sole is designed to maintain a stable posture with two points of ground contact, then the running stability is improved, but the heel-up state maintenance may hinder natural heel movement
Solution Approach 1:
The sole achieves stable two-point ground contact through local rigidity differentiation: the metatarsophalangeal joints region maintains higher rigidity to provide stable contact points during forefoot running, while the heel region has lower rigidity to allow natural sinking and movement. This resolves the contradiction by providing stability where needed without restricting natural heel movement.
Data Source
AI summary
In the stable posture, in which path length from the origin to the distal end is L, intersection between the sole bottom surface and line perpendicular to the reference line through position of 0.45×L is C, intersection between the sole bottom surface and line perpendicular to the reference line through position of 0.60×L is D, and sole is in contact with the ground at points C and D, the sole bottom surface at the heel portion is separated from the ground to be in a heel-up state, and an inequality, θ≥5 is satisfied wherein θ is an angle formed by the ground and line that connects the heel central position of 0.15×L with the metatarsophalangeal joints position of 0.68×L. The sole compressive rigidity is relatively lower at the heel-up starting position than at the metatarsophalangeal joints position.