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5 min readrunning / endurance

4% in the lab, 1% in the race: how to pick a super shoe

I put around 5,000 km a year on my legs, and a pair of racing shoes now costs more than the race entry. The number behind that price came out of a Colorado lab in 2017: a Nike prototype cut the energy cost of running by 4% 1. Six years later, seven elite Kenyan runners tried the same class of shoe on a treadmill in Munich, and one of them ran 11.3% worse in it 3.

What the research shows.

Wouter Hoogkamer, Rodger Kram and their co-authors tested 18 high-caliber runners at 14, 16 and 18 km/h, in six 5-minute trials. The prototype paired a compliant, resilient midsole foam with a stiff embedded plate. It lowered metabolic cost by 4% on average against two established racing shoes, and all 18 runners improved in it 1. Eliud Kipchoge raced the production version to a world record.

Nike funded that study, so the replication matters. Kyle Barnes and Andrew Kilding ran an independent randomized crossover with highly trained men and women, comparing the Vaporfly against a conventional marathon shoe and against track spikes. Economy improved 4.2% over the adidas Adizero Adios 3 and 2.6% over the spikes 2.

Three findings since then have narrowed where the 4% applies.

Dustin Joubert and Garrett Jones put 12 men through eight shoes at 16 km/h: seven carbon-plated racers and one traditional flat. The Alphafly came out around 3% better than the flat. The Hoka Rocket X and the Brooks Hyperion Elite 2, both built on EVA rather than PEBA foam, landed at 0.08% and 0.53%, inside the measurement noise 4. The foam separated the shoes; the carbon plate on its own did not.

Joubert, Trace Dominy and Geoffrey Burns then took the Vaporfly Next% 2 down to recreational speeds with 16 runners, against a mass-matched control shoe. At 12 km/h (roughly 8:03 per mile) oxygen cost fell 1.4%. At 10 km/h (9:40 per mile) the gap shrank to 0.9% and stopped reaching statistical significance 5. The shoe still helps slower runners, at maybe a third of the headline figure.

Race results land in the same range. Jamie Langley and Ben Langley analysed 971 marathon performances from 99 elite men between 2012 and 2021, splitting them into 299 races run in advanced footwear and 672 in traditional shoes. Mean race speed went from 5.386 to 5.441 m/s: 1.0% faster, or 79 seconds over the distance 6.

The 4% average hides the runners it fails.

Melanie Knopp and her co-authors ran the study that should make you cautious about buying on a review. Seven elite Kenyan men (mean half-marathon 59:30) and seven European amateurs each ran in three models of advanced footwear and a racing flat. The Kenyan responses spread from an 11.3% drawback to an 11.4% benefit. The Europeans ranged from a 1.1% drawback to a 9.7% benefit 3. A pooled meta-analysis in the same paper confirmed a medium average benefit across the literature. The average is the figure the marketing quotes, and individual runners sat anywhere along that spread.

Perception makes the spread harder to read from the inside. Kim Hébert-Losier's group gave 24 female recreational runners two identical pairs of Vaporfly Next% 2 for 6-minute economy trials. One pair was presented as elite advanced footwear; the other was spray-painted black and described as a knock-off. Oxygen consumption and energy cost came out the same in both. Comfort ratings did not, and 87.5% of the runners preferred the pair they had been told was genuine, rating it more enjoyable, less difficult and less likely to injure them 7. Comfort and perceived effort tracked the label, while the oxygen cost stayed flat.

The protocol.

  1. Read the foam before the plate. Look for PEBA or Pebax in the midsole description. In the eight-shoe comparison, the PEBA models sat near 3% while the two EVA-based carbon shoes returned 0.08% and 0.53% 4. A plate over ordinary foam buys nothing you can measure.
  2. Test at the pace you will race. The Vaporfly benefit fell from 1.4% at 12 km/h to 0.9% at 10 km/h 5. If your marathon pace is 6:00 per km, run the comparison at 6:00 per km.
  3. Run two sessions, with the order reversed. Same loop, same hour, similar weather. Each session: 3 km easy, then 2 x 10 minutes at race pace, one rep per shoe, 5 minutes jogging between. Put the new shoe second in session A and first in session B, so fatigue and warm-up land on both.
  4. Compare heart rate at matched pace, or pace at matched heart rate. One number per rep, four numbers total.
  5. Keep the shoe only if it wins both sessions. Knopp's runners landed anywhere from 11.3% worse to 11.4% better 3, so treat your own response as a spread rather than a constant. Two sessions that disagree mean the difference sits inside your day-to-day noise, and the cheaper pair wins.
  6. Have someone else hold the numbers until both sessions are done. The 87.5% preference for the pair labelled genuine came from the label alone 7. Reading your splits between reps lets that expectation pick the winner for you.
  7. Save the pair for races and your two hardest sessions a week. Every figure above came from 5 or 6 minutes on a treadmill in a shoe with low mileage. The published trials are short, and none of them followed runners long enough to say what the foam returns after 500 km, or what the shoes do to injury rates over a season.

Book the two test sessions before the shoe arrives, and put them three weeks out from your race. A disappointing answer then still leaves you time to race in the old pair.

Sources.

  1. Hoogkamer, W., Kipp, S., Frank, J. H., Farina, E. M., Luo, G., & Kram, R. (2018). A Comparison of the Energetic Cost of Running in Marathon Racing Shoes. Sports Medicine, 48(4), 1009-1019. doi.org/10.1007/s40279-017-0811-2
  2. Barnes, K. R., & Kilding, A. E. (2019). A Randomized Crossover Study Investigating the Running Economy of Highly-Trained Male and Female Distance Runners in Marathon Racing Shoes versus Track Spikes. Sports Medicine, 49(2), 331-342. doi.org/10.1007/s40279-018-1012-3
  3. Knopp, M., Muñiz-Pardos, B., Wackerhage, H., Schönfelder, M., Guppy, F., Pitsiladis, Y., & Ruiz, D. (2023). Variability in Running Economy of Kenyan World-Class and European Amateur Male Runners with Advanced Footwear Running Technology: Experimental and Meta-analysis Results. Sports Medicine, 53, 1255-1271. doi.org/10.1007/s40279-023-01816-1
  4. Joubert, D. P., & Jones, G. P. (2022). A comparison of running economy across seven highly cushioned racing shoes with carbon-fibre plates. Footwear Science, 14(2), 71-83. doi.org/10.1080/19424280.2022.2038691
  5. Joubert, D. P., Dominy, T. A., & Burns, G. T. (2023). Effects of Highly Cushioned and Resilient Racing Shoes on Running Economy at Slower Running Speeds. International Journal of Sports Physiology and Performance, 18(2), 164-170. doi.org/10.1123/ijspp.2022-0227
  6. Langley, J. O., & Langley, B. (2024). The effect of advanced footwear technology on elite male marathon race speed. European Journal of Applied Physiology. doi.org/10.1007/s00421-023-05341-x
  7. Hébert-Losier, K., Pfister, A., Finlayson, S. J., Esculier, J.-F., Lamb, P., & Beaven, C. M. (2025). Are super shoes a super placebo? A randomised crossover trial in female recreational runners. Footwear Science, 17(2). doi.org/10.1080/19424280.2025.2458330

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