Focus on running shoes have always been on the midsole foam technology as well as the upper mesh design and colors. But, what is less well known is the strong influence of the outsole on the performance of the midsole foam in absorbing shock and stress. Specifically, the thread pattern of the outsole affects the stress distribution on the foot from the ground through influencing how the midsole functions in absorbing stress.
Taking the Formotion pads on the heel and forefoot of the outsole of Adidas Duramo 8 as an example (Figure 1), the pads changes the way the Cloudfoam midsole reacts to stress and loading. Specifically, daily experience in wearing the Adidas Duramo 8 for walking reveals that the forefoot Formotion pad makes the forefoot region of the shoe more responsive to turning motion; thereby, providing a mechanism by which the torsional stress of turning your feet could be dissipated, which helps enable a more comfortable hinge of the feet.
Figure 1: Formotion pads on the heel and forefoot of the Adidas Duramo 8 critically affects the performance of the heel and forefoot Cloudfoam midsole in shock absorption. More importantly, experience in daily use of the shoe reveals that the Formotion pads changes the characteristics of the Cloudfoam midsole in corresponding areas of the shoe.
On shock absorption, close examination of the Formotion heel pad also point to the important role in which the outsole heel pad changes the characteristics of the one piece Cloudfoam midsole. Specifically, the slightly flexible nature of the Formotion heel pad changes the shock absorption feature of the heel part of the Cloudfoam midsole; thus, endowing the one piece foam technology with differentiated shock absorption characteristics. Hence, without the added cost of creating a multi segment midsole foam able to withstand differing load levels depending on its location within the midsole, creative outsole design such as the introduction of the embedded Formotion pads in Adidas Galaxy 3 and Adidas Duramo 8 provide a ready, simple and low cost means for introducing, in a budget shoe, sophisticated shock absorption technology suitable to the anticipated load levels in daily walking and load bearing tasks such as light jogging.
Collectively, innovations in outsole design and incremental evolution of existing technologies in high end performance running shoes have provided Adidas with a creative solution to the technically challenging problem of endowing a budget walking cum jogging shoe with fairly complex shock absorption capabilities at a low price. Daily experience with the Adidas Duramo 8, which features a heel and forefoot embedded Formotion pad, provided a lens into how the slightly flexible segmented heel and forefoot outsole enables slightly greater compression of the Cloudfoam in the corresponding areas; thereby, providing added support to areas likely to experience higher stress levels in hinging a joint (forefoot) and shock absorption on landing a stride (heel).
Category: sports medicine, sports science, mechanical engineering, material,
Tags: outsole, differentiated stress loading, midsole, heel strike. forefoot support,
Acknowledgement: Ng Wenfa thank Seah Kwi Shan for suggesting the theme of this blog post.