[caption id="attachment_79168" align="aligncenter" width="1024"] Image|Runner's World[/caption] PEBAX Shoes get slower over time - Sorry, Nike Víctor Rodrigo-Carranza et al. have released a study analysing the energy cost of supershoes but this time around they've looked at the difference between supershoe sole materials both when the shoes are new AND after 450km/300 miles of use. More: Arkema (PEBAX) More: EVA Science Source: Wiley The two key findings seem to be that PEBAX is better when new and that it degrades over time to perform similarly to EVA. I can't say I'm surprised with either of those findings and my own anecdotes would agree.Tip: Save your race shoes for races. Tip: Perhaps convert your race shoes to training shoes after a hundred miles or so and buy some more supershoes. Make Nike happy. Results There were significant differences in RE between conditions (p = 0.01; n2 = 0.17). There was a significant increase in energy cost in the worn PEBA condition compared with new (15.21 ± 1.01 and 14.87 ± 0.99 W/kg; p < 0.05; ES = 0.54), without differences between worn EVA (15.13 ± 1.14 W/kg; p > 0.05), and new EVA (15.15 ± 1.13 w/kg; ES = 0.02). The increase in energy cost between new and worn was significantly higher for the PEBA shoes (0.32 ± 0.38 W/kg) but without significant increase for the EVA shoes (0.06 ± 0.58 W/kg) (p < 0.01; ES = 0.51) with changes in step frequency and step length. The new PEBA shoes had lower energy cost than the new EVA shoes (p < 0.05; ES = 0.27) with significant differences between conditions in contact time. Conclusion There is a clear RE advantage of incorporating PEBA versus EVA in an AFT when the models are new. However, after 450 km of use, the PEBA and EVA shoes had similar RE.
