Compressive creep experiments were performed on an EVA foam from a running
shoe midsole of density 275 kg m(-3). Analysis revealed a 50% air loss from
the cells on a time scale of 10 hours, and a significant polymer contribut
ion to the creep response. The recovery process after creep is slow and inc
omplete, perhaps due permanent deformation or polymer recrystallisation. SE
M shows that surface cells are 'permanently' compressed. Modelling was perf
ormed of gas diffusion perpendicular to the stress axis, to predict the cre
ep curves, and along the stress axis to predict the development of a compre
ssed, gas-depleted surface layer. The latter considers the interactions of
cell strain, diffusivity, stress sharing between the polymer and cell gas,
and strain rate. The number of gas-depleted cells is predicted to increase
with the square root of the creep time.