REF-722 · Whiting, Hoogkamer & Kram, 2022 · Journal of Sport and Health Science, 2022 May;11 · Paper · PubMed
Super-shoe savings on a +/-3° treadmill: 3.83% level, 2.82% uphill (significantly less than level), 2.70% downhill (not significantly different)
A hilly course likely returns slightly less
Protocol
After familiarization, n=16 competitive male runners performed six 5-min treadmill trials (2 shoes × 3 grades) at 13 km/h (3.61 m/s), comparing Nike Vaporfly 4% against Nike Streak 6 at level (0°), uphill (+3°) and downhill (−3°). Metabolic power (W/kg) was calculated from oxygen uptake and CO₂ production in minutes 4-5.
Key Findings
| Gradient | Metabolic power saving vs conventional shoe (all p<0.001) |
|---|---|
| Level | 3.83% |
| Uphill (+3°) | 2.82% |
| Downhill (−3°) | 2.70% |
The saving is present at every gradient. Uphill it was significantly smaller than on the level (p=0.04, ES 0.561); downhill it was not statistically different from level (p=0.17, ES 0.356).
Authors' conclusion: on a course with uphill and downhill sections, the metabolic saving and hence the performance enhancement "would likely be slightly less overall" than on a perfectly level course.
Practical Application
In 16 competitive male runners at 13 km/h, Vaporfly 4% shoes cut metabolic power versus a conventional racing shoe by 3.83% on the level, 2.82% uphill at +3° (significantly less than level) and 2.70% downhill at −3° (not significantly different from level). Expect a slightly smaller benefit on a hilly course than on a flat one, as the authors conclude.
The uphill saving was about a quarter smaller than the level saving (2.82 vs 3.83%); the downhill point estimate was lower still, but that difference was not statistically significant.
Inference, not tested: this partly explains why flat-road numbers need not transfer to trail and hilly racing — before even considering traction, stability and ankle demands, which this study did not measure.
Not from this paper; the base's own practice: if an athlete is choosing where to chase a personal best, the shoe advantage is one more small argument for a flat course.
Do not read this as "super shoes do not work on hills" — savings of 2.70-2.82% were still measured on both grades.
Limitations
n=16, competitive males, single laboratory, treadmill, one speed (13 km/h). Small and narrow.
Only ±3° tested — roughly a 5% grade (tan 3° ≈ 0.05). Steep trail climbs and descents are far outside this range and are not addressed.
Treadmill gradients do not reproduce trail surfaces, footing, braking demands or technical descent.
One shoe pairing from one generation of the technology.
Metabolic cost only; no performance, stability, muscle damage or injury outcomes — all of which matter more on descent than economy does.
How this entry was checked and changed
Why this level
regraded 2026-09-27 from B: controlled crossover, n=16
Content correction 2026-09-27
"Largest on level ground" / "a quarter to a third less" -> uphill was significantly smaller than level (p=0.04), downhill was not statistically different (p=0.17); now stated, with the 13 km/h speed.
Level B -> B+: controlled crossover with n=16 (rubric). Sport line narrowed to running (treadmill study; trail transfer is discussed in the text).
Course-choice advice labelled as the base's own practice; trail-transfer point labelled as inference.