Research shows economy gains at slower paces, but they’re smaller and not guaranteed.
It’s no coincidence that running records have been falling in droves in the era of super shoes. While researchers still may not be able to fully explain how the technology works, they have shown that the high energy foam, curved carbon-fibre plate, and rocker geometry that first appeared in the Nike Vaporfly 4% in 2017 provide competitive runners a 2.7–4.2% boost in running economy. In other words, thanks to these shoes, runners need 2.7-4.2% less energy to run the same pace — meaning that they can conserve that energy to run farther or expend it to run faster.
But much of the research into super shoes has been tested at running speeds of 4:37 minutes/km or faster. Translated into marathon times, that means the science is applicable to someone who runs a marathon in 3:15 or faster.
So, can the majority of non-elite runners also get an edge from super shoes? The answer, probably yes, but less.
Research for non-elites
Dustin Joubert, Ph.D., a kinesiology professor at St. Edward’s University in Austin, Texas, likes to do research, in his words, ‘for the people’. This is how he came to conduct a study looking into whether super shoes, specifically the Nike ZoomX Vaporfly Next% 2, confer the same running economy advantage to athletes who run at slower paces.
‘There’s a lot of people who don’t fit under the umbrella of the speeds that have been tested in all this laboratory research, and a lot of people are asking: Should I spend my money on this? Do they work for slower people?’ said Joubert. ‘That was the next logical question to me.’
To answer the question, Joubert and his colleagues recruited 16 runners — eight men and eight women with prior-year 5K PRs averaging 19:06 and 20:18, respectively — and had them complete two sets of four 5-minute running reps on a treadmill. Each runner ran one set at a 12 kilometres/hour pace (4:58/kilometre, which would be marathon pace for a runner with a 5K PR of 22:15), and the other set at 10K/hour (6:00/kilometre, which would be on the slower end of easy pace for that same 22:15 5K runner). Within a given set, the runners tested two different shoes: they ran one 5-minute rep in an experimental carbon-plated shoe, the Nike ZoomX Vaporfly Next% 2, and the other rep in a control shoe, the Asics Hyper Speed. Then, the runners repeated the reps but reversed the order in which they wore shoes (e.g., Asics first, then Nike).
The researchers chose the Asics Hyper Speed as the control shoe because it lacks the technology of the Vaporfly (carbon plate and advanced foam) but matches its mass. This was an important variable to match because mass affects running economy; a heavier shoe will require more energy to move and could therefore confound results. One earlier study compared the Vaporfly to runners’ everyday training shoes, but most regular training shoes are more than 100g heavier.
Economy advantages for 3:30–4:15 marathoners
The new study found that, on average, running economy was better in the Vaporfly than in the Hyper Speed. However, at these slower speeds, the improvements were smaller than at faster speeds: runners gained just 1.4% in running economy at 4:58/kilometre pace and 0.9% at 6:00/kilometre pace, compared to the 2.7–4.2% advantage runners gained at speeds of 4:37/kilometre or faster. (And, as we’ll see below, even those improvements came with a caveat.)
Joubert speculates that the reason for this difference comes down to how the foam in the shoes is working. Much of the running economy advantage comes from compressing the compliant/resilient foam in the shoes and then having that energy returned as the foam springs back. A faster runner who is generating larger ground reaction forces will compress the foam more than a slower runner who, because of their speed, isn’t generating as much ground reaction force.
‘The shoe is not creating energy for you; it’s only giving back what you put into it,’ explained Joubert.
Not everyone benefits
Before you decide ‘an advantage is an advantage,’ there is one other finding from this study that should give runners pause. While the results from the 16 test subjects showed a 0.9–1.4% average improvement in running economy, one third of the participants actually showed worse running economy when they ran at the 6:00/kilometre speed in the Vaporflys, compared to the control shoe. This finding diverges from the results of testing done on the Vaporflys at faster speeds, where runners experienced varying degrees of running economy improvement, but no one saw a detriment.
One possible reason has to do with the Vaporfly’s carbon plate. Research has shown that increased longitudinal bending stiffness, or the rigidity of a shoe underfoot, helps to improve running economy at faster speeds by reducing the amount of energy your foot requires as you land and push off from the metatarsophalangeal joint (where your foot connects with your toes). Joubert hypothesises that, at slower speeds, the stiff carbon plate might stop saving runners energy and instead create a need for more energy in order to get ‘up over’ the plate.
‘If the plate’s really stiff, maybe at these slower speeds that’s an impairment to economy,’ Joubert said.
