It’s late into a very hard interval training session on the ski erg. You’ve got three more 500 meter intervals to go and fatigue is beginning to set in. You feel hot, your muscles are starting to tire and mentally you begin to question your desire to finish.
Your nutrition, hydration and mobility work were all on point to before and to start the session. However, how much thought have you given to controlling your body temperature during the workout?
If you were like me, not very much.
I understood that if I was very cold I didn’t move well and that if I got extremely hot I could suffer a heat injury, but other than that I didn’t give it much thought at all. What I’ve discovered is that thermoregulation is an untapped realm of human performance that virtually no one in the Nordic world (or any other sport) is talking about or using.
Thermoregulation and Performance
In the summer of 2021 I heard a couple very interesting podcasts where a Stanford scientist, Andrew Huberman, was discussing how palmar (palms of hands) cooling could have incredible performance enhancing effects on workouts. He mentioned that the research was not his own but from his Stanford colleague, Dr. Craig Heller. Dr. Heller was finding that when comparing workout output in terms of number or reps and sets being able to be performed when using palm cooling during rest breaks vs. not, that the palm cooling allowed for improvements of 40-60% in terms of work volume. And..these findings were in high level Athletes like NFL football players.
Now, as a Physical Therapist, an anatomy and physiology nerd, strength coach and a person who basically lives and breathes human performance I was shocked to hear of this phenomenon. I had never been taught it and had never even heard of it. I was very curious to say the least. I wanted to know more…and test it out for myself.
Before we get into my own journey, let’s talk about the physiology of thermoregulation through the palms as it’s something that you already use without even knowing it.
Palm cooling is a way to leverage your inherent temperature regulation system. Our body temperature is centrally controlled in the brain at the hypothalamus. The hypothalamus receives temperature signals and then makes changes throughout the body in response. These responses can be both physical (sweating, goosebumps, etc) or mental (like decreasing motivation or taking some type of action).
There are peripheral ways to control temperature too. For instance there are highly specialized areas of our body that are especially efficient at either dumping body heat or receiving heat. These areas are covered with a type of skin called glabrous skin. Glabrous skin is hairless and is found in humans on the palms of the hands, soles of the feet and the hairless potions of the face. Glabrous skin has a special network of blood vessels below the surface called arteriovenous anastomoses (AVAs) which are direct connections of arteries to veins with no capillary beds in between. The absence of capillaries indicates that the blood passing through this system is not intended for carrying oxygen to muscles or removing carbon dioxide from the system.
The AVAs in these areas allow for the cooling or heating of the blood circulating through them and returning that blood to the body to either heat or cool it. Think about it, this is why when you are hot at night you stick your foot out from under your blanket. It’s why when you are cold you put your hands around a warm coffee mug. It’s why your mom knew to put a cool rag on your forehead when you had a fever. The reason we do these things is because our internal temperature can be efficiently regulated through our glabrous skin.
So how does all this matter during exercise, competition or exertion?
As we exercise the temperature of our body and more specifically the working muscle begins to rise. This rise in temperature becomes detrimental to performance as it eventually causes fatigue in two ways. First, at the muscle cell level, the rise in temperature affects enzymes that are responsible for continued contractions. The rise in temperature changes the enzyme’s configuration resulting in a decreased ability of the muscle cell to contract.
The second way increased temperature causes fatigue is mental. As our temperature rises the brain receives this signal and decreases the motivation to continue working. This is likely an evolutionary protective measure preventing us from working into heat injuries or death.
Increasing body temperature during exercise contributes to fatigue both physically and psychologically.
Dr. Heller, realizing this, put the glabrous skin and AVAs underneath to work by using them as a tool during exercise to combat that rising temperature. His research and that of others (this video does an excellent review of the research) has shown “palm cooling” to be effective in increasing training volume by delaying the onset of fatigue.
Again, upon learning all of this I was both curious and skeptical. I began the journey of trying to find a palm cooling device that I could use in my own experiments. There was not much to buy online, so I began to experiment with making my own. While developing prototypes I began to do my own testing and found that I was getting performance improvements of 15-30% with my own strict testing protocols - you can learn about my initial testing here.
I then began using the device with my strength and conditioning clients and they were also showing improvements in training volume. The skepticism turned to belief as I began to gain more knowledge and insight from months of daily use and by reading available research. Palm cooling is now something I use as a tool with all of my clients.
Let’s discuss the details of palm cooling as there is some nuance to how to use it to create a beneficial temperature regulating effect. First, the surface or material used to cool the palms cannot be too cold. Ice, for example, is so cold that it will cause vasoconstriction of the blood vessels. If the vessels constrict then the cool blood will not circulate under the palms. It seems that the effective range is between 45-60 degrees Fahrenheit. This is cool to touch, not cold. For reference, most water fountains and cold tap water out of a sink are set between 40-50 degrees (the perfect starting temp!). It is also ideal to cool both palms at the same time as maximizing the surface area will create a greater amount of cooled blood recirculating back to the body. Do not tightly squeeze the palm cooling device as that compression could also prevent blood from flowing through the AVAs underneath.
How long do I need to palm cool to get a benefit?
This is a very common question that still needs much more research. The early studies by Dr. Heller used 3 minute rest breaks between efforts to failure. These studies showed significant improvements. In my internal testing we are seeing 15-20% improvement in work completed when using 3 minute rest intervals. However, we are actually seeing 28-30% improvements when using shorter rest intervals of 60-90 seconds between efforts. When training my clients, I am handing them our palm cooling device between sets or intervals anytime we have at least 20-30 seconds of rest before the next effort. We start palm cooling early and often in the workout after the general warm up and movement prep.
Thermoregulation for Nordic Skiing
Now that you know about the science and physiology, let’s now discuss how to implement these ideas into your training or competition.
For weightlifting, powerlifting or strength training session:
- Bring the palm cooling device to your training session.
- Remember, the device or substance being used should be between 45-50 degrees - NOT ice cold
- Do your typical warm up - do not worry about palm cooling during this portion of the workout. It is still valuable to get your joints and muscles moving, mobile and ready for bigger efforts
- During the meat of your training, simply grab and hold the palm cooling device during the rest breaks between sets.
- Do this between all sets, not just the last 3-5 “very hard sets”. Begin your palm cooling early to delay the rise in temperature. It is very likely that you’ll notice that you are capable and willing to perform more of your “very hard sets” when palm cooling is used. This is how palm cooling creates long term gain. By allowing for increased training volume during a session and then ultimately over the course of a training cycle.
For interval training INSIDE on the ski erg
- Palm cooling on the ski erg during the off season is geared mostly towards interval training (programmed sets of specific amounts of work and rest) as opposed to long duration, sustained efforts.
- Interval training on a treadmill, rowing erg, ski erg, stationary bike inside or on a track or training loop outside makes palm cooling easy as you will always have access to the device between efforts or intervals.
When skiing OUTSIDE during training and racing:
- Palm cooling outside with a device while skiing will not always be practical. However, if the training is on a 5 kilometer loop (for instance) where the athlete returns to the same starting place for multiple efforts, a palm cooling device could easily be stashed and used between efforts.
- Before a ski race: After going through the warm up it may be beneficial to hold onto a palm cooling device for the last few minutes before the start of the race to bring body temperature back down. This theory has not been thoroughly tested so more research is needed in this area. However, the idea of starting the race from a lower temperature would be advantageous.
Other uses of palm cooling devices:
- Palm cooling can also be used as a sleep aid after a late workout or practice. Many athletes have difficulty getting their core temperature and overall sense of arousal under control after exercise or competition late in the evening. Palm cooling is reported by some athletes to assist in falling asleep under these circumstances.
If you would like to try palm cooling there are a number of hacks you can easily find with a google search. However, almost every hack out there is impractical for a training, practice or competition setting. This is what led to me turning my prototype into a device for sale.
Our device is called the Anti-Fatigue Charge Bar and it’s available at Avacooling.com. Our design is simple but effective and meets the needs for effective palm cooling. It’s practical for use where you train or compete, it will cool both hands with 1 device, it can be re-cooled by refilling it with cool water from a sink or fountain, and it’s affordable!
To recap, rising body and muscle temperature during exercise leads to fatigue both at the muscle cell and at the brain level by decreasing motivation. We can directly combat that rising body temperature through the method of palm cooling due to the special network of blood vessels underneath the skin. This can lead to increased performance in both training and competition by allowing for a greater volume of high quality sets, reps and intervals to be completed and by helping athletes become less fatigued as their competition progresses.
Palm cooling devices are now available for purchase that are practical, effective and affordable. Give it a try and see for yourself, we’d love to learn about the effect it has on you!
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