We do not ship to you yet. We will tell you when we do.
SCIENCE
The science of the moment between efforts. Why heat limits repeated performance, why the body sheds it through the palms, and how KYLA is built to use that.
01/THE PROBLEM
During repeated efforts, heat builds up inside the working muscles and across the core. As core temperature rises, the body starts to prioritise managing that heat over producing output.
So output drops. Not from muscular failure, but because the thermal load has become too high to ignore.
Most athletes train hard and rest passively. The moment between efforts, the one that decides the next one, goes untouched.
02/THE PRINCIPLE
Heat is energy. The first law of thermodynamics is clear about energy: it is never created or destroyed. It can only move, from a warmer place to a cooler one.
That is the whole principle KYLA is built on.
The heat your body produces during training does not disappear on its own. It has to go somewhere. Give it a fast, direct route out and it leaves. Give it none and it stays, and it holds your output down.
KYLA does not cool you by a trick. It is the route out.
03/THE MECHANISM
The body already moves heat exactly this way, and it has a surface built for it. The skin on the palms is glabrous: hairless and smooth. Just beneath it sits a dense network of arteriovenous anastomoses, specialised vessels that open under thermal load and route blood to the surface to release heat.
It makes the palm one of the most efficient heat-exchange surfaces on the body. You have felt it work in the other direction. Cup your hands, breathe into them, and they warm in seconds. Heat moves through the palms fast. KYLA runs that exchange the other way, and draws heat out.
This is not a design choice. It is physiology.
04/THE ENGINEERING
Holding something cold does not guarantee heat leaves your body. Heat transfer depends on how well the material in contact with your skin conducts heat, not on temperature alone. A low-conductivity material moves very little heat, even when it is cold. Hold a foam cup of ice water, then a metal rod at the same temperature. The metal pulls heat from your hand at once. The foam barely does.
KYLA Performance is engineered around the rate of heat transfer. Its internal construction draws heat from the palm rapidly and continuously, not only in the first moment of contact.
Inside each handle, a patent-pending internal distribution system connects the surface to the whole phase-change core. Heat that enters through your palm is spread into a large volume of cold material at once, instead of having to cross a growing layer of melted material at the wall. That is why the surface returns to 14 °C between sets and holds it for the whole session, where a solid cold object is warmest exactly when you need it most: on the last set.
Cold alone is not the answer either. Past a point the vessels in the palm constrict, blood flow to the surface falls, and heat extraction slows with it. The colder the surface, the less the body cooperates.
KYLA is built to sit in the narrow window where extraction is most efficient: cold enough to keep drawing heat, warm enough that the body keeps the blood flowing. Read our honest answer to whether palm cooling works.
The internal construction is patent pending.
05/THE COMPARISON
Most cooling methods feel cold without moving much heat out of the body. KYLA is designed to move heat, not just to feel cool. Below is how it compares to the methods athletes most often reach for between efforts.
One minute of KYLA, modelled
How long other methods would need to move the same core heat KYLA moves in one minute, in our heat-transfer model, at equal contact time. Lower is better.
Modelled at equal contact time. ±20% uncertainty band.
Modelled means calculated, not measured on athletes: we measured how fast KYLA moves heat in our lab and calculated the other methods from published values under the same conditions. Modelled over a 60-minute session, fifteen cycles of three minutes work and one minute cooling, at 25 °C ambient. Those rates are then normalised to equal contact time, so every method is compared minute for minute. ±20% uncertainty band.
THE METHOD, IN FULL
The metric throughout is heat physically removed from the body's core: the deep tissues, the blood, and the organs. It is not the heat absorbed by the cooling source.
A cold object can absorb a lot of heat without that heat coming from your core. If most of what it absorbs is local skin or local tissue, the body simply rewarms that area from the core afterwards. The net effect on core temperature is small.
That distinction explains most of the differences above.
Cooling methods do not all do the same thing. There are two jobs.
Perceptual cooling is what you feel. Cold on the neck, the wrists, or the chest registers as strong relief. It lowers perceived effort, makes the same workload feel easier, and can lower sweat rate. That is real, and it is why athletes use those methods. But it is decoupled from how much heat actually leaves the body. The athlete feels significantly cooler than they actually are.
Core cooling is the other job, and the harder one. It is heat physically removed from the deep tissues, the blood, and the organs. It is the temperature that limits performance, and it is what this table measures.
KYLA delivers both. The palm is one of the most thermally sensitive surfaces on the body, so cold contact there lands as immediate relief, the felt experience our athletes describe. And because the palm is glabrous skin, that same contact also moves real core heat through the AVA network. One surface, two jobs.
Most methods give you only one. KYLA gives you both.
These figures are modelled, not directly measured in a controlled calorimetry experiment. We have a first-principles thermodynamic model and a ±20% uncertainty band on most rows.
Direct calorimetric validation of KYLA against the comparison methods is planned, and we will publish those numbers when they are available. If you want the underlying calculations or to discuss the methodology, get in touch.
This comparison uses a single 60-minute training session, structured as 15 cycles of 3 minutes work followed by 1 minute of cooling. Ambient temperature is 25 °C, typical of indoor training or moderate outdoor conditions.
Each method is applied during the 1-minute rest where it makes sense. Continuously worn methods, like a cooling vest, ignore the cycle structure and apply throughout. The comparison above then normalises every method to equal contact time, so a method worn for the full hour is not credited for the extra exposure.
The athlete in the model is heat-stressed: core temperature about 38.5 °C, palm skin about 36 °C, neck and torso skin about 34 °C. These are realistic values for someone 20 to 30 minutes into hard interval work.
The body has dedicated heat-release channels in glabrous skin: the palms, the soles, and parts of the face. These contain arteriovenous anastomoses (AVAs), specialised vessels that act as direct radiators for core blood. When open, they can move enormous amounts of heat per cm² of contact.
Non-glabrous skin (neck, torso, forearm) lacks these channels and couples poorly to the core. Cooling it mostly cools the local tissue, which the body rewarms from the core later.
The numbers make this concrete. A cooling vest covers roughly 8,000 cm² of torso skin. Two palms holding KYLA cover about 200 cm², roughly forty times smaller. But per cm² of skin contact, the palm can move on the order of fifty to a hundred times more core heat. That is the AVA mechanism, in numbers.
This is why ice on the neck, despite being very cold and having lots of surface area, removes very little core heat. And why a small palm contact in the right place can match or beat a vest forty times its size.
Take a surface far enough below skin temperature and the body shuts local blood flow down as a protective reflex. Ice on the skin can paradoxically remove less core heat than a warmer, properly tempered surface, because the very cold surface stops the blood flow that carries core heat to the cooling surface in the first place.
KYLA is designed around that trade-off. Cold enough to drive heat transfer, warm enough to keep the body’s heat-release channels open.
KYLA (two hands). Palm contact at 14 °C, 60 W sustained per cycle. The PCM latent budget supports all 15 applications with margin.
Cold drinks. 500 ml at ~10 °C tap water, sipped at 33 ml per cycle. That is 500 ml per hour, below the 600 to 800 ml per hour gut absorption ceiling. Each sip warms in the stomach to body temperature, releasing about 3.5 kJ of cooling per drink.
Cooling vest. PCM at 15 to 20 °C, worn continuously. Modelled against published research on cooling vest performance (Reilly & Cable, Bongers, Pryor, Schauer & Stevens).
Ice bags. 250 g of ice in a thin plastic bag, 60 s contact per cycle. Includes both heat absorbed from skin contact and from ambient warming between uses.
06/THE RESEARCH
Heat extraction through the palm has been studied for decades, at sports science institutions including Stanford, and across repeated independent trials since. The mechanism is well documented in peer-reviewed literature. You do not have to take our word for it, and you should not have to.
What KYLA adds is the application: a tool engineered to use that mechanism well, in real training, in the moment between efforts.
Our own performance testing is first-party and ongoing, and an independent study with Umeå University is underway. We keep that line visible. The mechanism is proven. Our product's own numbers are still ours to prove.
07/COMMON QUESTIONS
Does palm cooling lower core temperature?
In the published studies, cooling the palms during rests slowed the rise in core temperature during repeated efforts and let athletes do more work before fatigue. It does not make you cold; it removes heat the body is already trying to shed. The studies are listed, with links, on our studies page.
How cold should a palm cooling device be?
Around 10 to 16 °C. Below that the vessels in the palm close and less blood reaches the surface to be cooled, so a colder device removes less heat, not more. KYLA holds 14 °C by construction.
How long do you hold it?
Sixty to ninety seconds per rest, both hands, as many rests as the session has. The first minute does the work; what you feel afterwards is the surface returning to 14 °C for the next set.
THE EVIDENCE
Independent research, none of it funded by us. Results vary, and some found no effect. Those are on the studies page too.
The full studies behind palm cooling, and exactly how we tested KYLA in training. And for the questions that push back hardest, good reasons to doubt us.
KYLA Performance™ is the handle built around the pathway on this page. What it buys you is the end of the session: the sets you would otherwise have cut short. In the last published trial that was 15% more lifting volume than lifters who only thought they were being cooled. Wang et al., 2026 → The First Run ships October 2026.
Reserve KYLA Performance™