A Comparison of the Energetic Cost of Running in Marathon Racing Shoes

Abstract

Background: Reducing the energetic cost of running seems the most feasible path to a sub-2-hour marathon. Footwear mass, cushioning, and bending stiffness each affect the energetic cost of running. Recently, prototype running shoes were developed that combine a new highly compliant and resilient midsole material with a stiff embedded plate.

Objective: The aim of this study was to determine if, and to what extent, these newly developed running shoes reduce the energetic cost of running compared with established marathon racing shoes.

Methods: 18 high-caliber athletes ran six 5-min trials (three shoes × two replicates) in prototype shoes (NP), and two established marathon shoes (NS and AB) during three separate sessions: 14, 16, and 18 km/h. We measured submaximal oxygen uptake and carbon dioxide production during minutes 3-5 and averaged energetic cost (W/kg) for the two trials in each shoe model.

Results: Compared with the established racing shoes, the new shoes reduced the energetic cost of running in all 18 subjects tested. Averaged across all three velocities, the energetic cost for running in the NP shoes (16.45 ± 0.89 W/kg; mean ± SD) was 4.16 and 4.01% lower than in the NS and AB shoes, when shoe mass was matched (17.16 ± 0.92 and 17.14 ± 0.97 W/kg, respectively, both p < 0.001). The observed percent changes were independent of running velocity (14-18 km/h).

Conclusion: The prototype shoes lowered the energetic cost of running by 4% on average. We predict that with these shoes, top athletes could run substantially faster and achieve the first sub-2-hour marathon.

Fig. 1

Exploded view of the Nike prototype shoe that incorporates a newly developed midsole material and a full-length carbon-fiber plate with forefoot curvature, embedded in the midsole

Fig. 2

A rigid foot-form (shoe last) was mounted to the material testing machine actuator and snugly fit into a fully-constructed shoe. The actuated foot-form compressed the midsole in the vertical direction to match the displayed general time history of the vertical ground reaction force, producing insole pressure patterns similar to those recorded during running at 18 km/h

Fig. 3

We performed mechanical testing on three marathon racing shoe models. (Top left) The Nike Zoom Streak 6 (NS) midsole comprises lightweight EVA (ethylene-vinyl acetate) foam, a rearfoot Zoom air bag, 23 mm heel height, and 15 mm forefoot height. (Top middle) The adidas adizero Adios BOOST 2 (AB) midsole comprises BOOST foam made with TPU (thermoplastic polyurethane), 23 mm heel height, and 13 mm forefoot height. (Top right) The Nike prototype (NP) midsole comprises a new ZoomX foam made with PEBA (polyether block amide), an embedded carbon fiber plate, 31 mm heel height, and 21 mm forefoot height. (Bottom) Force-deformation curves, peak deformation, and energy return metrics for each shoe during vertical midsole loading with a peak force of ~ 2000 N and contact time of ~ 185 ms (Table 2). As vertical force is applied, the shoe midsole deforms (upper trace in each graph). Then, as the shoe is unloaded, the force returns to zero as the midsole recoils (lower trace in each graph). The area between loading and unloading curves indicates the mechanical energy (J) lost as heat. The area below the lower traces represents the amount of elastic energy (J) that is returned

Fig. 4

Over the three velocities tested, runners in the NP shoes used an average of 4.16% less metabolic energy than the NS shoes and 4.01% less than in the AB shoes (both p < 0.001). The AB and NS shoes were similar (p = 0.34). Values are the gross energetic cost of running. NS Nike Zoom Streak 6, AB adidas adizero Adios BOOST 2, NP Nike prototype

Fig. 5

Average vertical (F _z; top) and anterior–posterior ground reaction force traces (F _y; bottom) in the three different shoe models for runners with rearfoot strike pattern (n = 8) (left) and midfoot or forefoot strike pattern (n = 10) (right) during the 16-km/h trials. Force traces are normalized to body weight (BW). Initial impact and active F _z peaks were greater for the rearfoot strikers in the NP shoes. F _z recordings for mid/forefoot strikers were similar in the three shoes. NS Nike Zoom Streak 6, AB adidas adizero Adios BOOST 2, NP Nike prototype