Nike Vaporfly 4% - can these shoes really make you run faster? with Wouter Hoogkamer | EP#179
The Nike Vaporfly 4% running shoes are supposed to improve running economy by 4%. Wouter Hoogkamer, PhD, is one of the researchers who found out that this improvement is actually legit. What's more, he has researched how much faster that improvement in running economy could make you. In today's episode we discuss the Vaporfly 4% shoes, running shoes in general, running economy, breaking two hours for the marathon, and more.
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In this Episode you'll learn about:
- The Nike Vaporfly 4% shoes, and how Wouter and his colleages at the University of Colorado verified that they can reduce the energetic cost of running a given speed by 4%.
- Running economy, and how improvements in it translates to improvements in speed. Slow runners may benefit more from the 4% shoes than faster runners.
- Footwear in general, and the tradeoff between cushioning (which is good for running economy) and weight (which is bad for running economy).
- The impact of drafting in running - how much energy it can save you?
About Wouter Hoogkamer
- I am from the Netherlands and am currently a post-doctoral researcher at the University of Colorado in Boulder.
- I have studied mainly neuromechanics, biomechanics and energetics of how people walk and run.
- Most recently I have focused on running, but have also been doing some cycling research.
- I'm a runner myself, I started out on the track running 400m in 48s.
Over time I slowly progressed to being a marathoner, with a current PB of 2:32:50.
I rang that time at CIM in Sacramento, and really enjoyed that course.
- We have been studying biomechanics and energetics of running in various ways.
- More recently we started to focus on the role of footwear.
- Before I joined my current research lab, we had already come back from the rebound of barefoot running, where we knew it wasn't necessarily always better to wear the lightest shoe out there.
The shoe actually has a function. The cushioning function of shoes has been shown to save you energy.
- We then did a study looking at how footwear mass costs you more energy and slows you down.
We had runners doing time trials on the indoor track.
- Our most known study was on the Nike prototype shoe, which eventually turned into the Nike Vaporfly 4% shoe.
- When the shoe became available I got myself a pair, and I've been happily wearing them for some half and full marathon races.
I really enjoy them.
Investigating the Nike Vaporfly
- I've been following shoe research for a while and there have been small improvements in running economy.
For example early on when the Nike Air shoes were released they were a little better than the EVA shoes.
- Some people in the early 2000's were using carbon fibre plated shoes, and they saw a 1% improvement in running economy.
- When the Adidas boost was introduced and first studied that was shown to have a 1% benefit.
- When Nike first presented their prototype I was thinking it was going to be another 1% improvement.
We've been making shoes for a long time so it felt like we were just making steady progress.
- When we started testing the shoe we had to find 18 runners that were able to run a sub-31 10km, and also had to wear size 10 shoes!
Being in Boulder was great for that because we managed to find them.
- We had them run 3 different velocities:
1) Slightly faster than a 7-minute mile
2) 6 minute mile
3) 5:20 mile
In each of these we compared the new prototype shoes, the Adidas Adios Boost 2 shoe (which Kimetto was wearing when he set the marathon World Record), and the NIke Streak 6 (Nike's fastest marathon shoe at the time).
- When we started testing people, we saw very clear trends.
All 18 runners reduced their energy uptake when running in the prototype shoe, and on average over all 3 velocities it was by 4%.
- There was some variability - some people improved by 2% while others improved by 6% but everyone had a benefit.
- We thought about the variance a lot. Hypothesisng at first we thought maybe heavier runners may have more benefit from the new foam, but this wasn't the case.
We also saw overall that the heel strikers seemed to have a 4.5% benefit, whereas the forefoot and mid-foot strikers had more like a 3.5%.
However, this effect didn't carry through to follow-up testing.
- Overall, we couldn't find a lot of other factors that would influence which person would have a big benefit, and which would have a smaller one.
- If you have 18 runners and see a change in energetics it can be hard to find a determining factor that explains who is going to have big or small savings.
What does the 4% mean?
- We measured oxygen uptake and carbon dioxide production to get a measure of energy expenditure to compare the shoes.
- We used two baseline shoes, and originally we set out to compare it to the Adidas Adios Boost 2 that Kimetto wore, and we also included the Nike Streak 2.
It was 4.0% better than the Adidas shoe, and 4.1% better than the Nike shoe.
- We wanted to see that any effect we saw was due to the shoe properties, not just because they were lighter, so both Nike shoes had a small amount of mass added.
- So it was compared to the two fastest marathon shoes out there, but this is compounded by the fact Adidas and Nike sponsor the fastest marathon runners, so their shoes are more likely to run the fastest times.
- We're still trying to figure out exactly what the 4% energy expenditure saving means in terms of speed increase.
We do know that it's not a 1:1 relationship.
- We typically measure running performance and energy cost is the classic 'if you go faster you use more energy' -but it doesn't mean if you go 4% faster you use 4% more energy.
They are not linearly related.
- More recently we did an overview of the literature of different studies which measured how energy costs increases with velocity.
Most of those studies are performed on treadmill studies, allowing you to control the speed, but it means there is no air resistance.
Recently we combined all those studies and added information from a wind tunnel study showing if energy cost increases with velocity on a treadmill, it'll increase even more outside because of air resistance increasing energy cost.
Collectively these showed that an increase in speed with a 4% improvement in running economy depends on how fast you are running to start with.
- If you ran a 3-hour marathon you'd get around a 4% for 4%, but thinking about Kipchoge and his 2 hour marathon, because he's running so much faster it would only come down to a 2.5% speed increase. This would take off 3-minutes.
When you're slower your energy cost does not increase that steeply with increases in velocity, which suggests that specific benefits in running economy would allow a bigger gain in speed.
- With the paper we recently published we released an excel sheet to help people calculate the improvements they can expect.
For a 4-hour marathoner, assuming a 4% increase in running economy, you will run 4.2% faster.
This takes off 10-minutes of your marathon time.
- We are assuming the 4% carries over to these speeds as we did not test the shoe anywhere slower than 3-hour marathon time.
I cannot make the claim that a 4-hour marathoner will get a 4% increase in running economy on average.
However we do know that if you go to a lab and know this intervention saves you X%, then as a 4-hour marathoner you'll be slightly faster than that X%.
Cushioning/weight tradeoff in running shoes
- If you add more cushioning, the shoe is going to be heavier, we know this trade-off exists.
- Some people saw benefits with barefoot running, but others didn't see benefits.
- Around 2012, people from our lab in Colorado grouped all these studies together and looked at it more closely.
They started to see that the studies that saw benefits for barefoot running often used fairly heavy shoes as a baseline for non-barefoot running (350g+).
If your baseline shoe weighs 350g, if you take it off there may well be a benefit!
However in other studies that used 150g shoe as baseline did not find the same improvements, and sometimes it was worse, if they took the shoe off.
- This was followed up with another study where they took the cushioning out of the shoe and put it on the surface - they had a big treadmill with rollers, and they reached out to Nike who provided them with some foam.
So rather than having the EVA foam in the shoe they had big slabs which they put around the treadmill belt.
This enabled us to test energy cost of running - all the runners were barefoot on a rigid treadmill, compared to barefoot on a rigid treadmill with 1cm of EVA foam on top of it.
They clearly quantified that the benefit of having a soft landing can save you 1.5% of energy.
You take the mass of the shoe out of the equation, because the cushioning is on the surface, and the benefit of cushioning is 1-1.5%.
This was just with the traditional EVA foam of the time, but since then Nike has developed Airvac, Adidas has developed Boost foam which is 1% better than EVA, and the new Nike foam that's in the Vaporfly is even better than that.
Other brands have their own foams - e.g. Flyte foam. All are a combination of EVA optimised for energy return and softness, and likely better than the one used in the study at the time.
- Nike built the Vaporfly because they decided to forget about mass, and build a shoe that improves everything else - valuing cushioning and energy return properties.
The new foam they implemented turned out to be really light, even though this wasn't the goal!
- EVA stands for ethel vinyl acetate and is the most common foam you'll see in any running shoe around, except the Adidas boost which is a different material.
Most training and race shoes from different brands will have some sort of EVA because it's durable and soft, but the energy return properties are not ideal.
Different brands use different procedures for mixing the foam with other foams and more rubbery substances to add the benefits of durability, cushioning and optimise energy return.
- The Boost foam started from a different material and a second new Nike foam is different as well.
How long do the Vaporfly 4% last
- We didn't really quantify this in our study directly.
- For the study we made sure none of the shoes went over 30 miles, and at that point we sent them back for material testing and found they were still good as new.
I am aware, and have experienced myself, as soon as you go closer to 200 miles things start to function less well.
- However, I haven't seen any specific data on this for these shoes.
- I haven't put my shoes through a lot of miles yet - I only use them for races because I know they may not last as long.
Other biomechanical factors involved in running economy
- There are a lot of different studies with small sample sizes that seem to indicate one thing may be more important than another.
- From a biomechanics perspective, I believe most people self-optimise their own running form and unconsciously find their best way to run.
- Thinking about biomechanics in a broader scale we did some interesting thought experiments related to this 2-hour marathon concept, thinking about how we can improve running performance by tapping into biomechanics.
One of the things that came out was running behind other runners.
We're away of the benefits for drafting in cycling but it does seem to hold that running behind another runner does save you energy.
- The data that is out there is very old, it's from a 1970 wind tunnel test with one runner behind another runner.
At that time they did see that the metabolic savings were around 6% of energy cost, which was independent of running economy.
This indicates that whether you're running at a 2-hour pace, or a 4-hour pace, you will get a 6% benefit in energy cost from running 1m behind another runner.
This may be too close unless you're running behind someone with a very similar gait to you, but there's definitely benefits.
- If you have a race with a significant tailwind on one section, if you could rotate like you do on a bike taking turns in the lead, you could get some benefits there.
- We also quantified the benefits of downhill running.
If you start at the top of a high mountain and run down you can run faster, but if you're talking about marathon distances the damage over time builds up.
We looked at IWAF regulations for what is record eligible and they said you can drop a maximum of 42m over the 42km marathon race.
We quantified if you do exactly that how much faster can you run (compared to a completely flat course) - we found it saves about 1 minute at Kipchoge pace.
Most marathons have slight hills and bridges where there is a change of elevation, and every time you run up and down it's going to be worse than running on a level.
Estimating the second lactate threshold
- We have been doing some cycling shoe research recently which we are still working it.
- I found it interesting that when you ride at a steady speed, up to 150 watts, there's not necessarily a difference in your efficiency whether you're wearing carbon fibre shoes and cleats, compared to normal pedals and your Nike shoe on top of it.
We did find that as soon as it comes to high power outputs there's definitely a benefit of the cleats and cycling shoes.
- It's interesting to see that if you're just wearing your Vaporfly 4% on the bike in a triathlon you may even get some time savings from not changing your shoes in transition.
However this is specifically for steady state cycling, and most triathlon courses will force you to slow down into turns and speed up again, and there may be some hills etc.
Every time there is a change in intensity there may be a benefit from having a more secure connection to the pedal.
- Particularly in shorter races, saving time in transition may be particularly beneficial.
- As long as your power isn't too high and you're not pulling your back put up enough to lift off the pedal, you may not need the cleats.
- If you're a high power output ride it obviously may not help, but it could be something to thinking about for those on the lower end of the power output scale.
Rapid fire questions
- What is your favourite book, blog or resource related to triathlon or endurance sport?
- The Lets Run website - it keeps me sharp!
- What is your favourite piece of gear or equipment?
- My Nike Pegasus Turbo trainer shoes. They're more affordable than the 4% shoes but they have the same foam. I use them more for runs and keep my Vaporfly 4% for races.
- What is a personal habit that has helped you achieve success?
- Dedication! I'm dedicated, I run first thing in the morning and it helps me think things though. I'm dedicated to the work I do.
Links, resources and contact
Links and resources mentioned
- Nike Vaporfly 4% time savings Excel spreadsheet
- A Comparison of the Energetic Cost of Running in Marathon Racing Shoes
- The Biomechanics of Competitive Male Runners in Three Marathon Racing Shoes: A Randomized Crossover Study
- Extrapolating Metabolic Savings in Running: Implications for Performance Predictions
- How Biomechanical Improvements in Running Economy Could Break the 2-hour Marathon Barrier
- Reflecting on Eliud Kipchoge’s Marathon World Record: An Update to Our Model of Cooperative Drafting and Its Potential for a Sub-2-Hour Performance
Connect with Wouter Hoogkamer
- On Twitter - @Woutersinas
Connect with host Mikael Eriksson
Hi! I'm your host Mikael,
I am a full-time triathlon coach and an ambitious age-group triathlete. My goal is podium at the Finnish national championships within the next few years.
I first started the website Scientific Triathlon in autumn 2015 as a passion project to share my learnings with a larger triathlon audience. Later on, in early 2017 I started the podcast That Triathlon Show.
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