by John Quiggin on February 23, 2020

Like most recreational tri-athletes, I don’t pay much attention to what’s happening in the top levels of the sport, let alone in the separate worlds of swimming, cycling and running[1]. But I took notice last year when Eliud Kipchoge ran a marathon distance in under two hours, a barrier long thought to be unbreakable, and one that reminded my of my failed attempts to break four hours over the same distance.

Kipchoge had plenty of help in his effort, including pace runners (providing an added drafting benefit) and a guide car projecting laser light on to the track to ensure exact pacing. These non-standard features mean that the time doesn’t count as a record for the marathon event.

Apparently, the biggest boost, however, came from his shoes, Nike’s recently released Vaporfly’s which incorporate a special carbon plate and a foam designed to return as much as possible of the energy expended from the impact of each pace. In subsequent events, runners with Vaporflys have produced winning times as much as 4 per cent faster than would be expected. And, it seems, the benefit is just as great, or even greater, for middle-aged slowpokes.

As with similar innovations in swimming and cycling, there was a lot of pressure to ban these technological marvels. But the International Olympic Committee, unwilling to take on the might of Nike, decided to allow the shoes, while trying to limit further innovations.

So, should I lay out $A300 or so for a pair of these marvels, which apparently may last for only a couple of hundred km (YMMV)? For the moment, I’m not going to. I’m going to have one more try to break four hours, and for this purpose I’m racing against my (not quite as old) self, not other competitors or even the clock. Once the technology becomes general, I’ll no doubt adopt it like everyone else.

In the meantime, what really appeals to me is the claimed capacity of cooling wristbands to lower body temperature. Even in moderate temperatures, I end events drenched in sweat and temperatures in Queensland aren’t always moderate. Does anyone have any experience/thoughts on this?



Brian 02.23.20 at 1:46 am

A quick read says a runner generates 600 – 1300 watts of heat.
Heat (in watts) = 4 x [your body mass (kg)] x [running speed (meters/second)]
If you’re on a bike and have an ergometer telling you how many watts you are generating, I’d multiply that by around 4, because about 25% of muscle energy is converted to motion. The advantage on a bike is that you have a higher airspeed, so you get better evaporation.

But, some athletes are more efficient than others, so they won’t generate as much heat. Top athletes you can usually see smooth economy of motion.

Heat dissipation has to keep up with that heat production. Mostly it does.
Runners/cyclists get up to around 38.3 C (101 F) core temp and the body tries to stay there. Heat shock proteins are a major part of conditioning for endurance. They stabilize cells and act as chaperones to get proteins to fold properly.

Anyway, let’s assume that at speed X, you are producing Y watts and disappating Y watts. Call it 1100 watts of heat you are dissipating, just barely. Then you speed up a bit, and you are producing X+10 watts of heat. You can’t dissipate the heat anymore, not quite. So you need to dump 10 watts.

The article says the athletes increased 3.86% in aerobic capacity. So, let’s accept that number and call it watts. 1100×0.0386 = 42.46 watts that this wrist unit can dump from one wrist.

I don’t think that’s out of the question certainly. the hands are evolved to dump heat into. This little unit on the wrist doesn’t have to supply all that energy. It just has to create a better heat gradient on your wrist and the metal on the hot side needs water to evaporate more effectively.

I think the numbers work ok. The key to understanding this is similar to understanding an economics of how the marginal trades determine price. It’s that last little bit that pushes you over the edge that you need to deal with. Handle that, and your price won’t spiral out of control.

If it works that well on one wrist, I’d try it on two. And this could be an interesting technology if paired with light solar panels to wear in extreme weather.


hix 02.23.20 at 3:46 am

” And, it seems, the benefit is just as great, or even greater, for middle-aged slowpokes.”
Thats not what i´ve heard(radio so cant find it anymore). They are supposed to only amplify the effect of an already favourable physis – mostly foot form but also weight and hight that most people especially westerners dont have.


oldster 02.23.20 at 12:52 pm

“The article says the athletes increased 3.86% in aerobic capacity. So, let’s accept that number and call it watts.”

Wait — why should we accept this number?

I mean — I’m not going to fight the rest of your math. But accepting the number means accepting that the wrist-band is somehow dumping a lot of heat somewhere. Where? How? It must be putting it into the air, by heating up the air (and evaporating water). But why think that less than 1 square foot of wrist-band is going to do that at a faster rate than the remaining 22 sq feet of the person’s body-surface? It doesn’t look like a heat-sink, and it does not seem to be optimized for air-flow in any way. Skin and sweat are already very good at turning heat into vapor and heating up the surrounding air — what makes this better?

“The device uses a thermoelectric module strapped to the wrist, with one side becoming cool and the other side becoming hot with the heat sinked away using water and patented nanomaterials.”

Oh! Patented nanomaterials! That’s different, then!

If this thing acts as an actual heat-sink, then it will be easy to demonstrate it in a lab, on a non-human heat generator, taking psychology and placebo effects out of the equation. Show us how it takes heat from one side and then puts it into the air, at a rate significantly faster than an equal area of human skin.

Otherwise, I call BS.


Cranky Observer 02.23.20 at 2:45 pm

If the shoe actually does return energy to the runner rather than dissipating it I’d be concerned about the long-term affect on the foot and lower leg systems (particularly bones). It could be one of those advances in athletic technology that helps top-level pros squeeze out that vital additional 0.5% at their peak but leaves them too damaged to walk at age 50. That’s a trade-off top-levels have made in many sports since the days modern medicine was first brought to bear on performance but perhaps not something the typical amateur wants to do.


Collin Street 02.23.20 at 10:22 pm

If it’s thermoelectric and as described then it’s a peltier effect solid state heat pump. Presumably the nanotechnology is some sort of nano-scale surface treatment to improve heat transfer rates over a small area.

Is it legit? It’s a wrist-sized fridge, it’s hard to see how.


Doug K 02.24.20 at 12:11 am

the shoes are worth about 2-3% improvement in time. There’s been quite a bit of research on them, some here in Boulder CO (link from my name), and it’s all been consistent in reporting that range of improvement.
So at 4 hours that’s 5 to 7 minutes. If I still had time goals for my running, I’d buy a pair of these..

The wristbands look like mostly nonsense. I say only ‘mostly’ since there is some evidence that cooling the hands is effective in reducing perceived heat. Because of the effects described by the central governor theory, this can in fact work to help improve performance.
One study,
Dennis A. Grahn, Vinh H. Cao, and H. Craig Heller, “Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment.” Journal of Applied Physiology 99: 972–978, 2005.

But the simple way to do this is just to clutch some ice in each hand, pick up a new block at each aid station. In dry conditions, wear a pair of cotton gloves and stick the ice in there. The cotton will add a bit of evaporative cooling and some extra surface area.

When I was racing marathons in S. Africa we’d basically dump ice water on ourselves at every aid station, squelchy socks but it helped a lot with staying cool..


Collin Street 02.24.20 at 2:08 am

… although doesn’t the neck keep more-level while running than the wrists do? lifting weights is dead work. And you could fit a bigger one, and like, cyberpunk cooling scarf dOOd.


Collin Street 02.24.20 at 2:09 am


Moz in Oz 02.24.20 at 3:22 am

Cranky Observer : but much of peoples foot and lower leg is already about optimising power return in sprung steps. Allegedly that’s one of the evolutionary advances that makes us great exhaustion hunters. So it’s possible that further mechanical optimisation is just boosting the existing system by some amount and will make little difference.

On the flip side it could just encourage old people to run on their heels and destroy their knees. But I hope not, that seems like a dumb idea.


faustusnotes 02.24.20 at 6:10 am

John, the whole point of sport is to end the events drenched in sweat, that’s a feature not a bug! Why would you wear these?


oldster 02.24.20 at 6:02 pm

Reading up on the Peltier pumps makes it more plausible to me that you can create a local sensation of coolness with sufficient power input. I have my doubts about the magnitude of the effect, given the power you can carry in a small lithium battery, and given that Peltier pumps are a lot less efficient refrigerators than traditional liquid-cycled ones, which are horribly inefficient already, and given that it does not have cooling fins or extended surface area or any of the features that you need to pump BTUs into the surrounding air.

But let’s say that it can cool a patch of your wrist by a degree or two, and that this then produces a change in your overall sense of coolness. Maybe that’s right.

Problem: now you run the risk of heat stroke much sooner, and with less warning.

Why? Because this little unit is not really cooling your core. It is not appreciably pulling watts out of your system. All that it is doing is spoofing your thermal regulation system, to give you the impression of being cooler, when in fact the rest of your body is hotter.

So now you go out and run a bit faster, and generate a few more watts, and you feel better, because the temperature on a small patch of your wrist went down by a degree.

But your core temperature just went up another two degrees, because you are working harder, and you don’t notice it, because this little thing makes your wrist feel cool.

That is really not a good outcome.

Professionals and people who train a lot in the heat may be able to survive the illusion. But people who are not heat-trained and who think this is actually cooling their system, are going to cook their brains.

And it comes back to the same problem as my first complaint: this unit is simply incapable of siphoning off enough heat from your body to make a difference to your overall core temperature. It’s too small, and the power it has available is too little. It may not be a mere placebo effect — maybe it actually can do some local cooling — but the magnitudes are all wrong. And a device that misleads your thermal regulation system is worse than useless — it’s harmful.


John Quiggin 02.25.20 at 4:31 am

Oldster, this sounds pretty convincing to me. I should just take a cold shower before the event, I guess.


ozajh 02.25.20 at 7:01 am

My own question about the Vaporfly shoe is whether or not it changes the nature of the sport. It would seem the from the perspective of results and records the answer is ‘Yes’, while at the more fundamental level the answer is ‘No’. The same thing happened in swimming about 10 years ago, and I note FINA now has very specific regulations about what can and can not be used in official competition so perhaps we will see athletics follow suit.
There are a lot of sports where the impact of material and design technology has been much greater. Tennis, for example, has changed utterly since the advent of metal racquet frames. (I am not suggesting it is better or worse, merely that it is now a different sport.)
And as an aside, I must express my wholehearted admiration for the 60-something Professor Quiggin being able to complete tri-Athlons where the run leg is a full marathon. Especially in Queensland! (That means he’s fitter now than he was in High School.)


Collin Street 02.25.20 at 10:58 am

But what the nature of the event is is cultural. I’m not a runner, so I don’t know what runners think running “is”.

[I sail… and we’ve been dealing with technological change for a fair while, so what we do is, we leave it up to each class, each type of boat, to work out its own rules. Each class develops its own culture and understanding. It can’t really be set out briefly because the rules complications take a while to explain, but the three big anything-goes development classes [int 14, moth, and a-class catamaran] each took radically different approaches to the development of hydrofoils because each class had a different understanding of what defined its boats.]


Tom 02.25.20 at 3:26 pm

Not sure about the Vaporfly but has anyone here done a gait analysis? I run 5 to 10k and, to get a bit faster, I did some interval training last fall and developed some pain. Some have suggested a gait analysis but I have not yet got a chance to do it.

As to shoes, I think that with 3D printing we will soon see personalized ones.

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