HOW TO CHOOSE A PALM COOLING DEVICE

The six questions

1. 1

   Does it hold the cold, or only feel cold?

   A solid cold object takes heat in only where your hand touches it, and takes less with every second as that spot warms up. Ask what is behind the surface.

   Why

   Your palm gives its heat to whatever it touches. In a solid cold object that heat has nowhere to go. The spot under your hand warms, a warm layer builds between you and the cold, and less heat crosses with every second. What keeps a surface taking heat is what feeds it from behind. Ask a maker how their surface is fed, not only how cold it starts. Ours is a patent-pending internal system built so the whole core feeds the surface. The engineering chapter goes through it.

2. 2

   How cold should it be?

   Cold enough to pull heat out, not so cold that the vessels in your palm begin to close. A surface at room temperature has little to pull heat into, and colder is not stronger. KYLA is built to sit around 14 °C at the surface. Ice and gel packs start far below that.

   Why

   Heat leaves through the heat vessels (AVA*) only while they are open. Push the surface too cold and they begin to close.

   *Arteriovenous anastomoses. How they work: Walløe, 2015. Temperature.

3. 3

   One hand or two?

   Two hands move more heat than one, though not twice as much, because both palms draw on the same blood supply.

   Why

   Both palms draw on the same central blood supply, so a second hand does not double what leaves. It still adds a second way out. A one-hand device leaves that unused. Our own model puts two hands at about 1.7 times one. (Why two hands is 1.7, not 2.)

4. 4

   How much heat leaves in one rest?

   What matters is how much heat leaves in each rest, short or long, not how long a device stays cold. Almost no maker publishes it. Ours is modelled, not yet measured, and we are building the rig to measure it.

   Why

   A device can stay cold for an hour and still move little heat in each rest. What counts is the heat that leaves in the seconds you actually hold it, rest after rest. That is a rate, and it is hard to measure under a real hand. Until someone publishes it, questions 1 and 2 are your best guide: what feeds the surface, and whether it keeps your palm open.

5. 5

   How long does one chill last, and how do you reset it?

   Count the time in your hand, not the time on the clock. One chill covers a full session: 30 to 35 minutes in your hand, not on the clock, about 90 to 105 minutes of training. To reset it, put it in the fridge overnight, or for five hours at the least.

   Why

   The minutes are added up across the session. A pair does not last longer than a single handle, because both cores drain at the same time.

6. 6

   Can you use it where you rest?

   A cooling station works where it stands. A handheld goes to the bench, the court and the side of the track, so it is in your hand the second the rest starts. Check that you can hold it with what you already wear: gloves, wraps, chalk.

   Why

   Heat leaves in the rests your session already has. A cooling station, such as an ice-water mitt with a pump or a chilled bench, can run for as long as it is filled or plugged in, but you have to go to it. A handheld goes with you, so the first seconds of every rest count. A battery handheld needs charging. A passive one needs a fridge or freezer between sessions. (Passive or battery-powered: what electricity buys you.)