What is Palmar Cooling?
It isn’t every day you see a top athlete step away during their performance to put a cold glove on their hand. During the U.S. Open, that’s exactly what we saw Djokovic do.
Turns out it’s something called palmar cooling which has been in development for over two decades now. The potential impacts on performance are surprising and it’s worth knowing about.
It started with DARPA (US Defense Advanced Research Projects Agency) who, in the early 00s, wanted to improve the performance of American troops in combat situations. They commissioned a team out of Stanford University to look into it – chiefly doctors Craig Heller and Dennis Grahn.
These two had spent years studying mammalian temperatures and discovered that bears were able to regulate their body heat without shedding fur as a result of the palms of their feet being remarkable so-called “portals” through which the blood can change temperature rapidly and effectively cool the entire body.
The Biology of AVAs and Glabrous Skin
This same principle occurs in humans. Known as arteriovenous anastomoses or AVAs, described as early as 1858 in Gray’s Anatomy (no, not that one), they’re essentially radiator-like structures that transport blood through veins and arteries, skipping the capillaries. Veins and arteries are high-flow vessels, whereas capillaries are low-flow vessels. Basically, it’s the optimal way to alter body temperature.
In the main, our body is a pretty great insulator. We still have hair follicles across almost all of our skin. There are three areas we don’t, though, and this skin is referred to as glabrous (no hair): upper face above beard level, soles of the feet and palms of the hand.
The palms of the hand are the easiest of these three to manipulate because, y’know, shoes. And sight.
How Palmar Cooling Prevents Muscle Fatigue
So…as you’ll know, when we exercise, we get hotter. This applies to our overall body temperature but also the temperature of our muscles too.
One component of muscular failure is the muscle itself overheating, this is known as reaching hyperthermic limits. We have enzymes critical for fuel consumption – the metabolism of glucose – which are temperature sensitive and shut down when they’re over 39.5 degrees and according to Heller, is “the most immediate impairment of muscle fatigue.”
Now, as we mentioned above, the body is a great insulator so putting an ice pack on your quads in between sets of squats is not going to cool the muscle down quickly enough for you to benefit on your next rep. However, by utilising the AVAs in the palms of our hands, we cool the blood fast, which is then circulated around our entire body and into the muscle, cooling it down “from the inside out.” This addresses the fatigue element linked with heat, allowing you to physically perform at a higher level for longer.
Heller and Grahn theorised that more blood and thus oxygen is available to the muscles when the body doesn’t have to route extra blood for cooling. It’s important to stress the idea of palmar cooling “doesn’t allow you to do work you couldn’t ordinarily do. It allows you to recover faster.”
When we rest in between sets, we aren’t accessing any energy that isn’t already in our system. We’re simply giving the body more time to recover before going again. Temperature is a massive component in our ability to push for higher rep ranges.
Evidence: Bench Press & Endurance Gains
There are a number of scientific studies in the field of palmar cooling, but numerous main studies have conflicts of interest due to being commercially involved with consumer products. The researchers are established in their field, but bear that in mind.
Individual studies have shown remarkable differences in fatigue/exhaustion – as shown here by tripling the number of dips before exhaustion and a 17-30% improvement in bench press performance, both across 6 weeks.
Non-athletes’ ability to perform on treadmills increased by 25% when using palmar cooling (8 people in the study).
Another found a 26% average increase in work capacity using palmar cooling, again tested on bench press, with sixteen participants.
And there’s also evidence to suggest the rapid reduction of heart rate through palmar cooling — linked with improved recovery.
Research aside, the number of sportspeople and teams who use palmar cooling in some form is numerous – ranging from the US Olympic squad, to UFC fighters, Djokovic and dozens of NHL/NBA teams. Earlier this year, Nike announced a shoe with temperature control in, too.
If nothing else, there’s certainly an appetite for professional performers to explore the potential gains.
DIY Palmar Cooling: How to Try it at Home
The benefits outlined above were demonstrated by cooling the hands during the rest period in-between sets. Controlled at three minutes per time. The device created by Heller and Grahn, CoolMitt, circulates water that’s 12 degrees. It’s super expensive though, so if you’re interested in trying it yourself via cheaper methods, you can.
The idea is to cool your hands, not have them cold. If someone else were to touch the palm of your hand, it should still feel warm. If it’s cold, you’ve entered vasoconstriction, which essentially means your vessels are “sealing up.”
Passing a frozen bag of peas from hand to hand in between sets is a rudimentary way of generating a similar effect. Probably only one to do if you have a home gym though… unless you’re looking to make it on Tik Tok.
Either way, let us know if you try it.
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