Deliberate Heat and Cold Exposure
“Why would you ever do THAT?!” That’s the first question everyone always asks when I tell them I’m doing deliberate heat and cold exposure. The answer is a word called hormesis. Hormesis means that by exposing your body to temporary short-term stressors, you become more resilient to stress in the long-term. Lots of things can be hormetic, like exercise, and certain foods like broccoli sprouts. But temperature has a profound influence on the body, which is why exposing yourself to the extremes of temperature (temporarily – we’ll get to that) is one of the most powerful things you can do for hormesis, and therefore one of the best things you can do for your health.
To best understand the science behind why deliberate heat and cold exposure works, we’ll look at the two separately (because they have different mechanisms and benefits), and then we’ll put them together in a way you can actually use.
First, let’s talk about heat. Heat is beneficial because it activates “heat shock proteins.” Yes, that’s really their name. These heat shock proteins are great because they repair DNA and proteins in our body, and that helps us live longer. Heat exposure also helps increase our metabolism. This is because most of the fat in our body isn’t metabolically active, but heat can turn some of this fat into what we call “brown fat,” which IS metabolically active. Heat also helps us release growth hormone, which helps us (duh) grow, but is also responsible for tissue repair and an even greater increase in metabolism. Finally, deliberate heat exposure has shown to decrease the release of the stress hormone cortisol over time, making us more relaxed.
So that’s a lot of science, but what is the overall effect on humans? A lot of the studies on deliberate heat exposure were done in Finland because sauna use is apparently part of their culture. Researchers from the University of Eastern Finland compared 2,300 people (specifically men) who only did sauna once a week with men who used the sauna more than that, four to six times per week. They followed them for 20 years and found that 49% of men who used the sauna once a week died, compared with just 31% of those who went four to seven times a week – a significant reduction in overall death. Frequent sauna use also showed a decreased risk of death from heart attacks and strokes, and it reduced the risk of Alzheimer’s disease. The net effect is that deliberate heat exposure is good for our blood vessels, our heart, and it increases blood flow to the brain.
So if heat is good, you’d expect cold to be bad, right? That doesn’t seem to be the case. Exposure to cold, specifically immersion in a cold tub, increases the hormones norepinephrine and epinephrine (the “fight or flight” hormones), and these are co-released with dopamine (a hormone involved in motivation and “more”). These hormones can increase agitation and fear, and they’ll make you want to get out of the cold bath – but the dopamine release is why cold baths can be rewarding and paradoxically addictive. People who spent an hour in 14 degrees Celsius water (57.2 degrees Fahrenheit) increased their metabolism 300% and increased their norepinephrine and dopamine release by 500% for two hours after the cold exposure. Surprisingly, they did NOT have increased levels of the stress hormone cortisol, which means that the stress on your body seems to be beneficial, not detrimental. (Just a note, you do not have to spend an entire hour in a cold bath to get benefits – we’ll go over the specific times below.)
Overall, deliberate cold exposure has been shown to enhance mental performance, mood, and metabolism, and it will decrease inflammation and even addictive tendencies. Cold exposure has the same effect on your fat cells as heat exposure does: it converts more of your fat to the metabolically active “brown fat,” which burns more calories and increases your baseline metabolic rate. Cold can also help treat addiction. One study showed that people who did deliberate cold exposure for 2-6 minutes three times per week had lower rates of addiction relapse, presumably because of the sustained release of dopamine that cold exposure creates.
Now that I’ve hopefully convinced you that deliberate heat and cold exposure are good for you, what are the protocols, tips, and tricks for incorporating it into your life?
Most people find it most useful to dedicate a time to alternate between heat and cold exposure. For heat, it’s optimal to use a sauna at about 170 degrees, but if you don’t have access to a sauna, then a hot bathtub will work. Either way, the temperature should be hot enough that you’re slightly uncomfortable at first, but not so hot that it’s dangerous. You CAN die from overheating, so don’t mess around! Over time, your body will adjust and you’ll find that you can stay in longer. Sauna is especially beneficial at night because after you get out, your body temperature will drop and it will be easier to get to sleep. It’s also more effective to do a sauna after fasting for two hours because this will help you release more growth hormone. And don’t forget to hydrate! If you’re doing it right, you’ll sweat a lot in the sauna, so the recommendation is to drink at least 16 ounces of water with electrolytes for every 10 minutes in the sauna.
For deliberate cold exposure, a cold bathtub is best, but a cold shower also works. Again, the temperature should be uncomfortably cold, but not dangerous. It’s best to move around a little in the cold bath, which breaks the thermal layer around you and makes you colder. It’s most effective if you stay in the cold bath long enough to shiver, because this releases succinate, which activates brown fat. Unlike sauna, however, do NOT do your cold exposure immediately before bed, as the increase in temperature after you get out will make it harder for you do go to sleep. And ingesting caffeine 1-2 hours before cold exposure has also been shown to increase the dopamine release afterwards. Finally, if your goal is muscle hypertrophy (e.g. strength), don’t do a cold exposure immediately after lifting. BUT if you’ve done endurance or high intensity cardio work, cold exposure immediately afterwards can help accelerate your recovery and reduce inflammation. Overall, the optimal time for cold exposure seems to be 11 minutes per week.
Protocol
Put it all together, and a good protocol looks something like this:
Drink coffee, eat your breakfast, then two hours later, do the following:
Four rounds of:
Sauna or hot: 3-5 mins
Cold: 3 mins
This will get you to 12 minutes a week of deliberate cold exposure and you’re done! End on cold so your body will naturally heat up and the effect of the dopamine release will be most prolonged.
As always, listen to your body. Never do a protocol without checking with your physician or considering your specific health conditions. Personally, I do cold exposure as long as I can stand it, up to three minutes. You can always adjust the time and/or temperature as your body adjusts over weeks and months.
Finally, there are a few other modalities of heat and cold that we haven’t addressed, specifically infrared saunas and cryotherapy. Infrared sauna isn’t as hot as a dry sauna, so you can stay in longer, and it’s thought to penetrate deeper. Cryotherapy cools your body down drastically for a short period of time and is thought to improve inflammation and recovery. I won’t spend much time on these for two reasons: there haven’t been a lot of studies on them, and most people don’t have them readily available. But if you do have access to those things, they do seem to be beneficial.
Summary
Tips for heat/sauna:
As hot as is uncomfortable but not dangerous
Sauna at 170 degrees is best, then hot bath, then hot shower
Best before bed
Best fasted
Hydrate
Tips for cold exposure:
As cold as is uncomfortable but not dangerous
Cold bath is best, then cold shower
Don’t do it before bed
Drink caffeine 1-2 h prior
Best if you get to the point of shivering
Don’t do it immediately after exercise if your goal is building muscle
Do it immediately after exercise if your goal is endurance/recovery
End on cold exposure if you’re alternating with heat
Aim for 11 mins per week