We’ve known for some time that elite runners can race really fast in the new in the shoes. Little more than a week ago% shoes. Eliud Kipchoge won last year’s Olympic Marathon and ran that Nike Zoom Vaporfly 4 in the shoes. Little more than a week ago, Shalane Flanagan CA Notice at Collection.
Shoes & Gear?
A new report just published by the journal Sports Medicine indicates the answer is a qualified yes. In fact, every runner tested at the University of Colorado, Boulder’s “Locomotion Lab”—18 out of 18—had better running economy in the Vaporflys than when they ran in two other racing shoe models (Nike Zoom Streak 6 and Adidas Adios Boost 2). This represents a rare 100 percent success rate in the world of human-effects research. The subjects included eight rearfoot strikers, and 10 midfoot/forefoot strikers, with the heel runners gaining a somewhat greater advantage.
Why the Findings Matter
Running economy is a measure of the amount of work a runner must do at a given speed. It is generally measured in distance runners at a pace at or just above what well-trained marathoners can maintain for 26.2 miles. If a runner’s economy improves, that implies that he or she can go faster and/or longer without building excessive fatigue. So while this study didn’t show that runners were What Explains the Study Results would CA Notice at Collection.
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“We were surprised by the magnitude of the effect, and that we saw savings in every single subject at all three running speeds,” lead author Wouter Hoogkamer said. (The runners ran at three different paces: 6:53/mile, 6:02/mile, and 5:21/ mile.) “Typically, when we test a new shoe, we see that some runners save energy, but for others, the shoe doesn’t fit their personal biomechanics, so they have an increased energy cost in the new shoe. I’ve never seen such a robust finding as we had with the Vaporfly shoes.”
While some runners’ running economy improved by as little as 1.59 percent and others by as much as 6.26 percent, the averages clustered tightly around 4 percent. This allowed Hoogkamer to estimate that a runner in the Vaporfly shoes might reduce the current marathon world record of 2:02:57 to 1:58:54. Of course, there are many potential differences between treadmill running and true marathon efforts.
To join the study, all runners had to complete multiple 5-minute repeats as fast as 5:21/mile without edging over their lactate threshold. In the report's funniest, most understated line, the authors reported, "It was challenging to recruit 18 runners who could sustain 18 km/hour below lactate threshold and also fit the available size M10 prototypes.”
Casey A. Cass?
Previously, it was thought that shoes of light weight—a We may earn commission from links on this page, but we only recommend products we back for fast running—could not be manipulated enough to produce more than a 1 or 2 percent improvement. The Vaporflys use a new lightweight foam (ZoomX, in Nike-speak) that is both soft (cushiony) and bouncy (with high energy return.) The technical terms are "compliant" and "resilient." The shoes also include a stiff carbon-fiber plate in the midsole to enhance ankle and foot-toe efficiency.
The foam is so light that it allowed Nike to construct an unusually thick midsole for a racing shoe. That’s why, on first sight, almost everyone mistakes the Vaporfly for a training shoe. The shoes have a heel height of 31 millimeters, compared to 23 millimeters for the Adidas Boost and Nike Air shoes used in the study.
In their paper, the researchers try to tease out the various factors leading to the substantial energy savings. The Vaporfly wins big on cushioning: It “deforms” twice as much as the other two shoes. That is, its pillowy cushioning allows the foot to sink downward twice as far as the other two midsoles. Usually, such highly cushioned shoes don’t have good energy return. The two properties have often been seen as opposites in shoe construction, and shoe companies are forever adjusting them to achieve optimal results. With newer foams, the obstacles are apparently diminishing. As the researchers note, “Compliance and resilience are not mutually exclusive.”
The new Nike foam also tested best for energy return. It returned 87 percent of the stored energy, compared to 75.9 percent for the Adidas model and 65.5 percent for the other Nike shoe. The researchers believe that the combination of great cushioning and energy-return explains 80 percent of the Vaporfly’s advantage.
But how does the greater running economy present itself? Surely, there must be a clear and simple biomechanical change that can be observed. Not so far. In the Vaporflys, the runners ran with slightly longer strides (lower stride frequency), slightly more contact time, and slightly greater peak vertical force. None of these changes were large enough to explain a 4 percent improvement in running economy. For example, subjects’ stride rates barely changed. While running at 5:21 per mile pace, they averaged a stride rate of 181 in the Vaporflys, 182 in the Adidas shoes, and 183 in the Nike Air shoes.
What’s Next in Shoe (and Performance) Breakthroughs?
Study author Rodger Kram and others have previously noted that softer midsoles (or treadmill surfaces) produce energy savings by allowing the knee to bend less. With less knee bending, the big quadriceps muscles are contracted less, and therefore less oxygen is consumed. However, the new study did not measure knee flex, so the researchers can’t identify that as a crucial factor. “We are currently performing follow-up experiments to get more insights into the exact biomechanical mechanisms at play,” Kram said.
Midpack marathoners will wonder if the Vaporflys would work for them at, say, 4-hour marathon pace and slower. Hoogkamer believes so. “We don’t have any actual data relating to 9:10 [per mile] pace,” he said, “but we noted a relatively consistent 4 percent savings at the three paces we tested. So it seems we could extrapolate this to the 9:10 pace. Those runners should see an improvement of 8.4 to 8.9 minutes [in a marathon].”
When Dennis Kimetto ran the current marathon world record in 2014, he wore a pair of Adidas Boost shoes. To help a runner get to 1:59:59, a shoe would have to offer a 2.5 percent performance enhancement. Could the Vaporflys manage that?
Theoretically, yes, though the performance edge isn’t a full 4 percent. That’s due largely to the air resistance of outdoors running versus a treadmill. Also, a 1:59:59 marathon would require a pace of 4:35 per mile—faster than any pace measured in the Colorado lab.
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When Hoogkamer made the necessary adjustments, he pegged the actual performance-improvement level at 3.4 percent. Voila, a 2:02:57 becomes a 1:58:54.
While the new Nike Vaporflys appear to represent a major leap forward in performance running shoes, they aren’t the last stop. Future shoes will bring greater enhancements. But it won’t be easy. “The options for improvement are diminishing,” Kram said. “Cushioned shoes can’t get much lighter than the 7 ounces of the Vaporfly shoe, and it is already delivering 87 percent energy return, so that figure can’t go much higher.”
The Colorado report was sponsored by Nike, which will cause some to cast a skeptical eye on the results. Kram’s response: “Nike came to us because we could design a bulletproof study, and I have lots of expertise and recognized integrity in the field. The money didn’t go to me. It paid my post-doc and grad students, and we compensated the subjects for their time. There is no way I would risk my scientific reputation built over 34 years to fabricate results. This was just a totally cool project. I love this stuff.”
