Impact of advanced footwear technology on running economy at slower running speeds: a randomised, cross-over investigation

Abstract

Introduction & Purpose: Compared with traditional running shoes, Advanced Footwear Technology (AFT) improves the oxygen cost of running (O2 cost) for athletes competing at fast speeds. Less clear are the effects of these modern shoes at the slower speeds commonly adopted by recreational runners, where it has been suggested that a minimum force might need to be exerted to result in metabolic savings. Therefore, this study primary aim was to assess the effects of AFT shoes on O2 cost at slow running speeds.

Methods: Fourteen moderately-trained runners (6 men, 8 women, age 25.5 ± 2.8 years, body mass index 21.7 ± 2.3 kg·m^-2, V̇O_2peak 49.8 ± 5.1 ml kg^-1·min^-1) ran at four speeds (5 min at 7.5 km·h-1, and 3 min at each speed of 9.0, 10.5 and 12.0 km·h-1) with three different footwear conditions: traditional running shoes (On Cloudrunner 2, TRA); AFT shoes (On Cloudboom Echo 3, CBE); and prototype shoes combining AFT and standard features (high compliance, energy return, and mass; On Prototype, MIX). A break of 15 min was given between shoes within a day. The full protocol was repeated on three different days by each participant. Throughout the protocol, gas exchange, heart rate and spatiotemporal variables were monitored. Perception of effort and shoe comfort (using visual analogue scales) were assessed at the end of each run.

Results: Combining all tested speeds, O₂ cost was lower for CBE compared with both TRA (-5.4 ml·kg^-1·km^-1, 95% CI: -6.9 to -3.9 ml·kg^-1·km^-1, p < 0.001) and MIX (-4.1 ml·kg^-1·km^-1, 95% CI: -5.6 to -2.6 ml·kg^-1·km^-1, p < 0.001), whereas no difference between MIX and TRA could be detected (95% CI: -3.4 to 0.8 ml·kg^-1·km^-1, p = 0.269). Differences in O₂ cost between shoes were independent of speed. Perceived effort was lower for CBE compared with TRA only (-0.2 points, 95% CI – 0.4 to -0.1 points), whereas no differences were detected for perceived comfort between any of the shoes (p = 0.377). No clear effect of footwear was detected for cadence, ground contact time, or leg stiffness. Comparing the most and least liked shoe models revealed preference for both lower O₂ cost and higher comfort, with larger effect sizes for comfort.

Discussion: The present data contradicts earlier studies suggesting the presence of a speed-dependent effect of modern racing shoes on metabolic savings. Diverging results might be due to lower variability in the current study as a result of multiple testing sessions per participant and speed.

Conclusion: AFT shoes can provide meaningful metabolic savings even at very low running speeds, with no distinguishable speed-dependence. These metabolic savings cannot be explained by changes in spatiotemporal variables. AFT shoes for recreational runners should be further improved to maintain metabolic efficiency while not sacrificing perceived comfort, which is a stronger determinant of shoe preference.