Biomimetic Design for Enhanced Shock Absorption in Sports Footwear: Optimization of Ostrich-Inspired Forefoot Cushioning Units of limited thickness

Significance 

Optimum sports footwear design requires the balance between comfort, performance, and injury prevention. Shock-absorbing performance is a fundamental functional attribute of sports shoe soles, especially in the forefoot region where the thickness is limited. Traditional designs often face challenges in optimizing cushioning without compromising stability and performance. The impact forces exerted during various physical activities can be substantial, which may lead to potential painful injuries including degenerative joint diseases, plantar fasciitis, muscle tears, and stress fractures. The primary challenge in this area is achieving effective shock absorption within the constrained space of the forefoot region of sports shoes. Most existing research and commercial designs focus on the heel region, where there is more space to incorporate cushioning materials and structures. However, the forefoot region demands innovative approaches to maximize cushioning without increasing the thickness excessively, which could affect the shoe’s performance and comfort. To this end, new study published in Composite Structures and led by Professor Rui Zhang, Liangliang Zhao, Qingrui Kong, Guolong Yu from Jilin University alongside Dr. Haibin Yu from Quanzhou Normal University tried to address the challenge of enhancing shock-absorbing performance in limited thickness conditions. The authors were inspired by the unique structure and material assembly of ostrich metatarsophalangeal joints and toe pads, which utilized traditional materials to assemble and process biomimetic cushioning elements. Through the coupling design of biomimetic structures and materials, high cushioning performance in limited space was achieved. The researchers developed a novel design for a forefoot bionic cushioning unit.

The research team validated the shock-absorbing performance of the bionic unit using finite element simulations followed by experimental testing using 3D-printed samples. The initial design incorporated various structural parameters such as cantilever angle, cantilever taper, cantilever spacing, and the thickness of the elastic energy-absorbing component. The finite element simulations provided a theoretical framework to understand the impact forces and deformation patterns. These simulations showed that the initial design could indeed absorb significant impact forces, but there was room for optimization. The 3D-printed samples were subjected to drop hammer impact tests to simulate real-world conditions. The authors’ findings from these experiments revealed that the optimized configuration of La:Lo:L3 = 60°:0.6:9 mm:3 mm, and the material ratio of T-4 significantly improved the shock-absorbing performance. Specifically, the peak negative acceleration of the forefoot bionic unit was reduced by 32.64% compared to the non-optimized unit. This reduction was an important finding because it demonstrated the effectiveness of the bionic design and material selection in enhancing cushioning performance.

Afterward, the researchers conducted further optimization to fine-tune the structural and material properties of the forefoot bionic cushioning unit. They systematically varied the cantilever angle, taper, spacing, and thickness of the elastic component to identify the optimal combination that provided the best cushioning performance. They tested the optimized structure again using both finite element simulations and physical drop hammer tests. These tests confirmed that the optimal structural configuration provided superior cushioning by dissipating impact forces more effectively. The key finding in these experiments was that the combination of structural design and material properties played a vital role in achieving the desired shock-absorbing characteristics and the optimized unit exhibited a balanced deformation pattern, efficiently distributing the impact forces across the entire unit.

The authors validated the practical applicability of the optimized bionic cushioning unit and produced sports shoes that incorporates the new design and compared them with control shoes. They conducted human wear experiments to evaluate the performance in real-world scenarios. A group of five male participants, aged 23-26, with varying body weights, performed a series of jumps from different heights (20 cm, 30 cm, 45 cm, 60 cm, and 80 cm) while wearing both the bionic cushioning sports shoes and the control shoes. Again, the authors’ findings from these experiments were promising and the bionic shoes exhibited a 23.7% to 29.8% increase in impact absorption compared to the control shoes. This significant improvement in cushioning performance was consistent across different jumping heights and participants of varying body weights. The peak plantar force values recorded during the tests were consistently lower for the bionic shoes, indicating their superior shock-absorbing capability. In all these experiments the peak negative acceleration and compression displacement were used as key indicators to evaluate the performance of the cushioning units. The optimized bionic unit consistently showed lower peak negative acceleration values compared to the control units. This finding was crucial as it indicated reduced impact forces transmitted to the lower limbs, thereby lowering the risk of injuries. Moreover, for the compression displacement, the optimized bionic unit demonstrated a balanced deformation, maintaining stability while effectively absorbing impact energy. This was particularly evident in the forefoot region, where the limited thickness posed a challenge for achieving optimal shock absorption. Indeed, the optimized design successfully mitigated this challenge, providing effective cushioning without compromising the shoe’s overall performance and stability.

In conclusion, the study by Professor Rui Zhang and colleagues developed a novel approach to designing sports shoe midsoles by drawing inspiration from the natural shock-absorbing structures found in ostrich feet. The proposed biomimetic design approach by the authors marks a significant departure from traditional methods that primarily focus on the heel region and often result in a trade-off between cushioning and stability. Manufacturers can incorporate the optimized bionic cushioning unit into their designs, offering consumers shoes that provide superior shock absorption and comfort. The new design promises to reduce the risk of injuries that are common among athletes and sports enthusiasts including plantar fasciitis, stress fractures, and degenerative joint diseases.

This design provides an innovative approach for the development of high-performance skydiving shoes, jump rope shoes, running shoes, and marathon shoes. This study was funded by the Science and Technology Development Planning Project of Fujian Province of China (No. 2022H6034) and the Science and Technology Development Planning Project of Jilin Province of China (No. 20220101014JC).

Biomimetic Design for Enhanced Shock Absorption in Sports Footwear: Optimization of Ostrich-Inspired Forefoot Cushioning Units of limited thickness - Advances in Engineering
Figure 1 Coupling bionic design of forefoot unit and heel unit for sports footwear
Biomimetic Design for Enhanced Shock Absorption in Sports Footwear: Optimization of Ostrich-Inspired Forefoot Cushioning Units of limited thickness - Advances in Engineering
Figure 2 Making in Sports footwear with bionic high cushioning units

Reference

Rui Zhang, Liangliang Zhao, Qingrui Kong, Guolong Yu, Haibin Yu, Multi-objective design and optimization of high cushioning bionic shoe midsole under limited thickness of forefoot, Composite Structures, Volume 324, 2023, 117560,

Go to Composite Structures

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