Baumann et al. 2025, midsole thickness and running economy

Sports Medicine - Open randomised cross-over trial in well-trained runners comparing entry-level shoes with 40 mm and 50 mm advanced-footwear prototypes. Thicker midsoles improved running economy: the 40 mm shoes by about 2.4% over entry-level, and a 50 mm prototype by a further 0.6 to 0.7% despite its greater mass. The 40 mm shoe was rated most comfortable; the 50 mm was less comfortable. The authors note the World Athletics 40 mm cap does not appear to be the point beyond which gains stop, while cautioning that an economy gain need not translate into performance.