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Document Title: Butler-AJSM-Dec06.shtml
Article Title: Interaction of Arch Type and Footwear on Running Mechanics
Authors: Robert J. Butler, PhD, Irene S. Davis, PT, PhD, and Joseph Hamill, PhD
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: December 2006
Volume 34, pages 1998-2005
Keywords: Biomechanics, kinematics, kinetics, forces, moments, foot, knee, shoe design, arch, shock absorption, impact, kinetic energy, high arch, low arch, midsole.
(Reference-denoting numbers appear in the same font and point size as the document text. As with all Knee Library documents, this article is provided in full-text form, complete with all figures and tables.)
Comments: The human arch is intricately linked with the shock-absorption characteristics of the foot. If you place a rigid filler underneath the arch of your foot, you will notice the dramatic increase in impact felt. While cushioning underneath the heel is always helpful, it cannot replace the shock-absorbing function of the arch. Ideally, the entire shoe is designed with shock absorption in mind. Of course, some compromise must be made between cushioning to absorb shock and firmness to prevent excessive motion of the foot, which could lead to ankle inversion or eversion injuries. (And, ankle injuries can lead to knee injuries, since ankle injuries are typically followed by the use of taping or stiffening via motion-restricting braces. The ankle is one of those joints which naturally moves in many ways, and any loss of this motion could translate into increased knee-injury risk.) With regards to a person's foot arches, severely flat-footed (i.e. no arch to speak of) or low-arched person would be expected to have less shock-absorption capability than someone who has high arches. How these attributes interact with shoe design is an interesting area of research. This study looked at a variety of footwear-related factors pertinent to the running gait, and in particular as influencing various types of injuries. A full biomechanical analysis, using a well-equipped gait-analysis laboratory (complete with a six-infrared-camera 3D motion-analysis system and floor-mounted force plates), enabled accurate quantification of the movements (displacements), velocities, accelerations, forces, and moments (torques) involved. Footwear is intricately linked not only to forces at the ankle (rearfoot), but also with the forces at the knee (and in fact, the influence affects the entire leg, as well as the spine). Clearly, shoe biomechanics can have a major effect on the knee. The authors chose their study variables with an eye towards injury causes. So, their foot-related variables reflected excessive pronation and ankle eversion. Their knee-related variables reflected compression (including impact loadings), shearing, and twisting at the knee. (Although this study was supported in part by a footwear manufacturer, the general findings are pertinent to the shoes from other firms too.) The authors found that running mechanics (and not structural attributes such as arch height) are the most useful parameter for shoe selection; ideally, every runner would undergo a complete gait analysis in a well-equipped biomechanics laboratory. The authors note that shoes designed for controlling foot motion necessarily are more rigid and provide less shock absorption than cushion trainer types.
ABSTRACT
Background: Running shoes are designed to accommodate various arch types to reduce the risk of lower extremity injuries sustained during running. Yet little is known about the biomechanical changes of running in the recommended footwear that may allow for a reduction in injuries.
Purpose: To evaluate the effects of motion control and cushion trainer shoes on running mechanics in low- and high-arched runners.
Study Design: Controlled laboratory study.
Methods: Twenty high-arched and 20 low-arched recreational runners (>10 miles per week) were recruited for the study. Three-dimensional kinematic and kinetics were collected as subjects ran at 3.5 ms–1 ± 5% along a 25-m runway. The motion control shoe evaluated was the New Balance 1122, and the cushioning shoe evaluated was the New Balance 1022. Repeated-measures analyses of variance were used to determine if low- and high-arched runners responded differently to motion control and cushion trainer shoes.
Results: A significant interaction was observed in the instantaneous loading rate such that the low-arched runners had a lower instantaneous loading rate in the motion control condition, and the high-arched runners had a lower instantaneous loading rate in the cushion trainer condition. Significant main effects for shoe were observed for peak positive tibial acceleration, peak-to-peak tibial acceleration, mean loading rate, peak eversion, and eversion excursion.
Conclusion: These results suggest that motion control shoes control rearfoot motion better than do cushion trainer shoes. In addition, cushion trainer shoes attenuate shock better than motion control shoes do. However, with the exception of instantaneous loading rate, these benefits do not differ between arch type.
Clinical Relevance: Running footwear recommendations should be based on an individual’s running mechanics. If a mechanical analysis is not available, footwear recommendations can be based empirically on the individual’s arch type.
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