Descriptive differences in physiological and biomechanical parameters between running shoes : a pilot study with a single-subject experimental design

Abstract: Running performance has increased immensely during the last few years, coinciding with multiple shattered world records in relatively short amount of time. Improvements in footwear material and design are likely reasons for this increase in running performance. Previous studies on the effect of footwear on running economy (RE), a determinant of running performance, have not included participant-blinding. Furthermore, they have yet to compare multiple carbon-fiber plated running shoes available for purchase, what differences there are across price ranges and shoe categories, and if there is such a thing as a placebo-effect. Aim: (1) Descriptively compare a set of heterogeneous running shoes, with regards to running economy, Foot Strike Type (FST), vertical oscillation, ground contact time, stride length and cadence; including (2) a ‘sham’ and ‘normal condition’ of the same running shoe model; and (3) explore the participant’s perception of the study-specific blinding protocol. Method: A Single Subject Experimental Study (N=1), comparing nine different shoe conditions using a crossover design. The assessment of RE was conducted using indirect calorimetry with mixing-chamber in a climate-controlled facility. Spatiotemporal parameters were assessed using a Garmin HRM-Run™, and foot strike type was visually assessed using a frame-by-frame approach based on 2D-video at 240 fps. Results: The average running economy across all shoe tests varied between 16.02 to 17.02 W/kg, with the ‘worst’ shoe costing 6.24% W/kg more than the ‘best’ shoe. The descriptive difference between the ‘sham’ and ‘normal condition’ were negligible and within the range of measurement error. Spatiotemporal parameters were overall descriptively similar between the shoes, with a few outliers who differed with regards to measure of central tendency or dispersion. FST differed between the shoes including the ‘sham’ and ‘normal condition’, but were overall consistent with the participant’s habitual FST. The study-specific blinding procedure was perceived to work well, but may also be improved in some remarks. Conclusion: Descriptive difference in some, but not all, physiological and biomechanical parameters were observed between the shoe conditions in this study, including the ‘sham’ and ‘normal condition’. Blinding procedures in experimental footwear research may be feasible and adopted with future studies.