Mechanical Ageing Performance of Minimalist and Traditional Footwear Foams

Authors

Nadine M. Lippa, University of Southern MississippiFollow
Paul K. Collins, Deakin UniversityFollow
Jason Bonacci, Deakin University
Scott G. Piland, University of Southern MississippiFollow
James W. Rawlins, University of Southern MississippiFollow
Trenton E. Gould, University of Southern MississippiFollow

Document Type

Article

Publication Date

1-2-2017

Department

Kinesiology

School

Kinesiology and Nutrition

Abstract

© 2016 Informa UK Limited, trading as Taylor & Francis Group. The aim of this study was to obtain a fundamental understanding of how running shoe midsole foam thickness contributes to footwear degradation using the heel and forefoot regions of traditional (TS) and minimalist (MS) running shoes. We hypothesized that ethylene vinyl acetate (EVA) foam midsole material properties and footwear degradation performance under a biofidelic mechanical ageing protocol would differ as a function of shoe type and thickness. Attenuated total reflectance Fourier transform infrared spectra indicated that the foam chemical compositions were similar and confirmed that all midsoles were composed of EVA copolymer. Differences in density and cell size were detected between shoes and thicknesses. MS foam was uniformly high density (ρ_MS = 240 kg/m³), while TS foam consisted of two co-molded layers with forefoot density (ρ_TS-FF = 250 kg/m³) greater than heel (ρ_TS-H = 160 kg/m³). Relative density and cell size values were generally proportional and inversely proportional to density, respectively. Degradation from mechanical ageing was greatest in the first 2 km of ageing, with the full ageing (21 km) resulting in an average 54% loss of energy absorption. Regardless of shoe type or foam microstructure, thicker and softer heel foams absorbed 83% more energy but degraded at a 49% faster rate. The fact that the heel degraded more rapidly than forefoot caused the drop to decrease at an equivalent rate for both shoe types. Overall, thickness was a greater predictor of average performance than microstructure variables for the present footwear conditions. However, the apparent drawback of thicker foam was exemplified by heel samples, which underwent a 1.4 mm greater loss of thickness and lost 550 mJ more energy absorption than forefoot samples.

Publication Title

Footwear Science

Volume

9

Issue

1

First Page

9

Last Page

20

Recommended Citation

Lippa, N., Collins, P., Bonacci, J., Piland, S., Rawlins, J., Gould, T. (2017). Mechanical Ageing Performance of Minimalist and Traditional Footwear Foams. Footwear Science, 9(1), 9-20.
Available at: https://aquila.usm.edu/fac_pubs/18396