Effects of longitudinal bending stiffness and midsole foam on running energetics

Abstract

Background: Advanced footwear technology has become common place in the competitive running world. However, a systematic exploration of the benefits of each of the primary components has not yet been presented. Purpose: To quantify running economy and step parameters in four different shoe conditions: PEBA shoes with plate, PEBA shoes without plate, EVA shoes with plate and EVA shoes without plate. Methods: Participants ran at 14 km/h (n = 8 males) or 12 km/h (n = 6 females). The shoe order was randomly assigned for the four shoe conditions, where the participants wore each shoe twice in a mirrored order. Results: There was a significant effect of the presence of the plate (-1.0%) as well as a significant effect of foam type (-1.0%). However, there was no significant interaction between presence of plate and foam type. Adding a plate significantly improved running economy for EVA (-1.3%) but not for PEBA (-0.6%). PEBA foam improved running economy, this was significant for the shoes without a plate (-1.3%), but not for the shoes with a plate (-0.6%). Step frequency and contact time were similar between shoes and not correlated to running economy improvements. Conclusions: Starting from a baseline condition with traditional foam without a plate, either adding a plate or using PEBA foam improved running economy with a similar amount (1.3%). Adding the alternate second feature non-significantly improved running economy with an additional 0.6%. The benefit of both technologies combined (1.9%) was smaller than the sum of its parts (1.3% each).