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Footwear cushioning was evaluated objectively using an impact tester and related to perceived levels of cushioning (PLC). To evaluate the perceived levels of cushioning during standing, walking, and running, 3 experiments were conducted with 20 participants in each experiment. A 7-point subjective rating scale was used to rate the perceived levels of cushioning. At the end of the experiment, the subjective perceptions of cushioning were also recorded. During standing and running, the perceived level of cushioning can be predicted from the time to peak deceleration and/or stiffness (or compression). During walking, however, the magnitude of the peak deceleration on the impact tester appears to be a good predictor of PLC. Impact characterizations can reveal important differences between materials and how they are perceived during activity. In addition, the results seem to explain and link the differences that exist in the ergonomics and biomechanics literature on cushioning. Applications of this research include the design and selection of materials for footwear, floor mats, and other supporting surfaces.
INTRODUCTION
Foot-ground interfaces exist in many different forms. Frequently the interface is a shoe or floor mat, and sometimes it is a carpet-like material, such as an Astroturf, providing specific biomechanical characteristics to help one perform effectively. Hence these interfaces can play an important role in improving functionality or performance, preventing injury, and reducing discomfort.
Human movement generally involves repeated loading at the foot-floor interface, resulting in force transmission through the human feet and toward the upper extremities. Proper cushioning attenuates these impact forces and protects the musculoskeletal system from potential injury (Schwellnus, Jordaan, & Noakes, 1990). The literature indicates that the term cushioning is used to describe only those aspects of the foot-floor interface that are concerned with reduction of the transmitted forces. As a result, the foot-floor interface literature is split into two distinct categories, related to injury and discomfort. In the biomechanics literature, injury has been linked to shock absorption, whereas the ergonomics literature primarily focuses on discomfort and has always made reference to the hardness or compression of materials, or both.
This paper is meant to develop a more unified approach to understanding cushioning. Aspects associated with cushioning - namely, injury, discomfort, and functionality - and their weaknesses will now be discussed. Cushioning and Injury...