Midsole Recess Structure for Running Ankle Stability

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Solution Overview

Problem

Existing sports shoes do not adequately reduce the change in angle of the ankle joint from landing to taking off during running, leading to increased foot fatigue.

Innovation Solution

A sole design featuring a recessed portion in the midsole with a plate embedded within, providing enhanced flexural rigidity and cushioning properties, which suppresses ankle joint movement and stabilizes the foot during the transition from landing to taking off.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the sole uses a conventional flat design, then the structure is simple, but the ankle joint movement is not sufficiently suppressed and foot fatigue increases

Engineering Contradiction:
Improvesole structureVSAvoidankle joint stability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The sole incorporates a curved contact surface that protrudes toward the ground, replacing the conventional flat design. This curvature allows the sole to better conform to the ground surface and foot anatomy, providing enhanced ankle joint stability while maintaining structural simplicity

Inventive Principle:
Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention modifies the geometric parameters of the sole by creating a recessed portion with specific depth and width ratios. The curved contact surface has a controlled protrusion height relative to the surrounding sole surface, optimizing the balance between structural complexity and ankle joint stabilization effectiveness

Inventive Principle:
Principle #35Parameter changes

2Ease of operation

If the sole adds more cushioning structures, then foot comfort improves, but the device complexity increases

Engineering Contradiction:
Improvefoot comfortVSAvoidsole structure
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The sole features a localized recessed portion with a curved contact surface concentrated in the forefoot region, rather than distributing cushioning structures uniformly throughout the entire sole. This localized approach enhances foot comfort in the critical forefoot area while minimizing overall structural complexity

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The sole is divided into distinct functional regions: a recessed portion with curved contact surface for cushioning, and a raised portion for structural support. This segmentation allows each region to perform its specific function optimally without requiring complex integrated structures

Inventive Principle:
Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The sole design effectively reduces the change in ankle joint angle, enhances cushioning, and maintains stability, thereby reducing foot fatigue and improving comfort during running.

Implementation Method 1

a plate 300 is embedded in the midsole 100, the flexural rigidity of which is larger than a flexural rigidity of the midsole 100

Methodology Applied
Scientific EffectFlexural rigidity:

Implementation Method 2

The sole design featuring a recessed portion in the midsole with a plate embedded within, providing enhanced flexural rigidity and cushioning properties

Methodology Applied
Scientific EffectCushioning:

Data Source

PatentEP4424196B1Sole and shoe
Publication Date: 2026.04.01 ASICS CORP
  • EP4424196B1 patent drawingFigure 1
  • EP4424196B1 patent drawingFigure 2
  • EP4424196B1 patent drawingFigure 3~4

AI summary

A sole (10) includes a midsole (100), and the midsole (100) includes a toe support portion (110), a midfoot support portion (120), and an intervening portion (140). The sole (10) includes a toe contact surface (11) and a midfoot contact surface (12). The intervening portion (140) has a recessed portion (142) having a shape recessed from an imaginary curved surface (IS) toward a side of a wearer's foot. A length between the imaginary curved surface (IS) and the recessed portion (142) is greater than or equal to 13% and less than or equal to 50% of a thickness of a portion of the intervening portion (140) where the recessed portion (142) is provided. The midsole (100) has a front side region surrounded by a front line (FL) and a rear line (RL), and an area of the recessed portion (142) in plan view is greater than or equal to 35% and less than or equal to 50% of an area of the front side region (AR1) in plan view.