Palm cooling is the practice of holding a cool surface, around 10 to 16 °C, against the palms of the hands during rest periods, so that heat is removed from the blood through the hand's specialised heat-release vessels and core temperature rises more slowly during repeated efforts. It is used between sets, at changeovers and in transitions, not during the effort itself.
Why the palm
The skin on the palms, the soles of the feet and the face is glabrous: hairless and smooth. Beneath it sits a dense network of arteriovenous anastomoses, vessels that open when the body is under heat load and route warm blood to the surface to shed heat. Per square centimetre, these surfaces move more heat than almost any other skin on the body. Under heat stress a disproportionate share of the body's heat loss goes through the hands, feet and face, which is why they feel hot first.
A cool surface held against the palm takes heat out of that blood on its way past, and the blood carries the loss back to the core. That is why a device the size of a handle can affect the whole body, and why the same device on the forearm does very little.
Cool, not cold
Below roughly 14 °C the vessels in the palm begin to close, and the colder the surface, the less blood arrives to be cooled. A colder device removes less heat, not more. The useful window is around 10 to 16 °C; a surface that holds near 14 °C is the design that cannot be set wrong. Ice and gel packs start below the window and drift.
Where the idea comes from
The research began at Stanford University in the early 2000s, where Craig Heller and Dennis Grahn showed that cooling the palm, first with a mild vacuum to keep the vessels open and later with plain conductive cooling, let subjects do more work in the heat and more repeated sets in the gym. Later studies at other universities tested the same idea without the vacuum, on bench press, pull-ups, sprints and time to exhaustion. As of 2026 there are more than twenty independent, peer-reviewed studies on palm cooling and performance; none were funded by us. They are listed, with links, on our studies page.
What the research shows, and does not
The consistent finding is more work before fatigue when the palms are cooled between efforts: more reps in the later sets, more repeated sprints, a longer time to exhaustion, with a lower perceived effort for the same output. The most recent strength study found 22% more lifting volume with palm cooling than without, and 15% more than a placebo device. The effect is on repeated efforts, not on a single maximal lift, and the studies are small; the direction is consistent, the size varies. Our own testing, with its limits, is on the methodology page.
Kinds of palm cooling device
Ice and gel packs. Start too cold and drift; fabric between the skin and the cold adds resistance. Cheap, and the weakest option.
Water-filled metal bars. Good contact, but still water behind the wall cannot move heat fast enough, so the surface warms within a single grip and the bar needs refilling after about ten minutes of use.
Phase-change cores. A material that melts at a fixed temperature holds the surface on that plateau until it is spent. With internal conduction paths the whole core supplies the surface and it returns to its plateau between sets. This is how KYLA Performance is built.
Battery-powered (Peltier) handhelds. Hold a set temperature for an hour or two, but move only a few watts of heat per palm because the hot side has nowhere to go in a handheld. Some are adjustable below the useful window.
Tethered systems. An ice-water mitt with a pump, or a mains-powered bench chiller. High output for hours, in one place.
How to use it
Sixty to ninety seconds per rest, both hands, as many rests as the session has. Hold, do not squeeze; a relaxed grip gives the most contact. The first minute does the work. Use it for palm cooling between sets, at the changeover, in the transition; not before the session as a substitute for a warm-up, and not during the effort.
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.
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.
How long do you hold it?
Sixty to ninety seconds per rest, both hands. Longer adds little; the next rest adds a lot.
Does it work for strength training or only endurance?
The clearest results are in strength training, where output is counted in reps across sets. Endurance and repeated-sprint studies show the same direction.
Is it the same as an ice bath?
No. An ice bath is used after training for recovery and cools the whole body from the outside. Palm cooling is used between efforts, during the session, and removes heat through the blood. Ice bath vs palm cooling. How palm cooling has been described in general media since the Stanford cooling glove in 2012 is collected on the press page.
KYLA Performance is a pair of palm cooling handles with a phase-change core that holds 14 °C. How it is built · Reserve KYLA Performance →