Effects Of A Carbon-Plated Racing Shoe On Running Economy At Slower Running Speeds

Advancements in running shoe technology, such as the inclusion of a carbon-fiber plate along with new, thicker midsole foams, have been shown to improve running economy. Running economy can be defined as the oxygen consumption (VO2) or caloric expenditure at a fixed running speed. Specifically in the Nike Vaporfly line of racing shoes, running economy improvements have been shown in the 2.7-4.2% range at running speeds of 14-18 km·hr-1. These previously tested speeds are relevant for runners completing the marathon distance in 3 hours and faster. However, it is unclear if the same running economy benefits are conferred at slower running paces. PURPOSE: Determine the effects of the Nike Vaporfly Next% 2 (NVF2) on running economy at 10 and 12 km·hr-1. METHODS: NVF2 was compared to a mass-matched, control (CTRL) shoe, the Asics Hyper Speed. Six male runners (34 ± 15 years, 72.9 ± 9.5 kg, 19.6 ± 8 % body fat, 5-km best: 20.6 ± 2.2 min) completed 4 x 5-minute trials at 10 km‧hr-1, followed by another series of 4 x 5-minute trials at 12 km‧hr-1 on the same day. There was a 5-minute seated rest between trials. Each shoe was tested twice at each speed in a mirrored sequence with the order counterbalanced across subjects. Metabolic and running mechanics data were collected and averaged. Dependent t-tests were used to make comparisons between shoes at each speed. RESULTS: There were no significant metabolic differences between shoes at 10 km‧hr-1, however the rate of caloric expenditure was significantly lower (1.1 ± 0.9%) in the NVF2 than CTRL at 12 km‧hr-1. CONCLUSION: In this preliminary data set, it appears that the NVF2 may still provide benefits to running economy at 12 km‧hr-1, however these benefits may be smaller in magnitude (1.1%) compared to previous research (2.8-4.2%) at faster speeds of 14-18 km‧hr-1.