Footwear reduces and redistributes lower extremity joint work in women runners

Twenty four females of US sizes W7 W8 W9 were recruited (35.3± 7.7 yr, 65.6 ± 13.4 kg) who ran at least 2 per week. Each ran on an instrumented treadmill at her preferred pace (averaging 10:15min/mile or 2.62m/s) for three minutes in five randomized conditions. Footwear consisted of the commercial Nike: Structure 22, Pegasus 36, Infinity React, Invincible ZoomX, and Vaporfly NEXT%. A size W8 sampling defined a large range in mechanical properties under custom loading: 232N/mm down to 133N/mm in compression stiffness and 7.0Nm/rad up to 15.1Nm/rad in longitudinal bending stiffness. Pelvisdown kinematics and underfoot kinetics were collected for the last two minutes of each trial. Data were processed using V3D and python. Statistical comparisons were made using RM ANOVA with Tukey’s post-hoc (alpha 1⁄4 0.05).