New Running Shoe Reduces the Energetic Cost of Running

Abstract

Running shoe features (low mass, cushioning, midsole bending stiffness) have been shown to individually reduce the energetic cost of running. Recently, energetic cost has been directly linked to time-trial performance. PURPOSE: To quantify the energetic cost of running in three marathon racing shoes: a prototype and two shoes currently available to runners. METHODS: 18 sub-elite runners (sub-31 min 10km at altitude or equivalent; altitude VO2max: 72.1±3.4 ml O2/kg/min) ran six 5 min trials (3 shoes × 2 replicates) in: a prototype shoe (NP), and two established marathon shoes (NS6) and (AB2), all equilibrated to 250g/shoe (the mass of AB2, size 10) during three separate sessions - 14, 16 and 18 km/hr. The order of the shoe conditions within a session and the session speed order were pseudo-randomized, mirrored and counterbalanced. The NP shoe has a novel, lightweight and highly resilient midsole and a carbon fiber plate that stiffens the shoe in longitudinal bending. We measured submaximal VO2 and VCO2 during min 3-5 and averaged metabolic rate (W/kg) for the 2 trials in each shoe model. Blood [La] measured after the last trial of each session and RER indicated running energetics were at steady-state (<3.0 mmol/L and <0.91, respectively). We compared the 3 shoes over 3 speeds using a two-way ANOVA with repeated measures. RESULTS: A significant main effect for shoe (P<0.0001) indicated the NP shoes required 4.0±1.3% (mean±SD) less energy than the NS6 and AB2 shoes (NP vs. NS6: P<0.0001; NP vs. AB2: P<0.0001), which had similar metabolic costs (NS6 vs. AB2: P=0.34): NP 16.45±0.89, NS6 17.16±0.92 and AB2 17.14±0.97 W/kg averaged across 3 speeds. Although the shoe × speed interaction effect was significant (P=0.0005), post-hoc analyses suggest that relative percent differences between shoes were similar at the 3 running speeds (all P>0.56). CONCLUSIONS: The new shoe reduces the cost of running by 4.0% as compared to two other established marathon racing shoes. This study was supported by Nike Inc. EF and GL are employees of Nike Inc., RK is a paid consultant to Nike Inc.