Effects of longitudinal bending stiffness and midsole foam on running energetics and biomechanics

The emergence of advanced footwear technology (AFT) has dramatically altered the world of distance running. Shoes featuring precise combinations of materials and geometry, centering around a stiff curved carbon fibre plate with a thick midsole comprised of highly compliant and resilient foam, have been shown to influence running economy. For instance, the Nike Vaporfly 4% was so named because of findings by Hoogkamer et al. (2018) that showed a 4% improvement in running economy. Further, the 4% improvement in running economy has resulted in a 2.3% improvement in elite marathon performance in men and women (Senefeld et al., 2021). However, previous literature has not been able to distinguish between shoe features while comparing across different shoes leaving the magnitude and mechanism behind the improvement in running performance unclear.