The sauna is one of the most powerful recovery tools available to athletes and regular gym goers however it is very underutilized. Most gyms will have them on site, built in rooms to make you the best you can be and most people don’t even bat an eye. The only reason I can think of for people to not use the sauna is ignorance. If you knew what it is capable of you would kick yourself for not using it sooner. Benefits such as improved cardiovascular potential, increases in muscular gain, expedite injury process, and brain health and longevity will all be talked about in this article.
We’ve all been at the point during a run where you’ve hit that wall, your heart is pounding, feeling fatigued and feeling hot. The increased body temperature you are experiencing is what is ultimately going to be the limiting factor for you going longer and keeping that same intensity. One way to push that limiting factor back is heating your body to those extreme temperatures separate from aerobic exercise.
There are tons of factors that improve from this heat exposure such as lower heart rate at similar intensity levels, lower core body temperature during exercise, higher sweat rates and sweat sensitivity (thermoregulation), increased blood flow to muscle tissue, which causes reduced rate of muscle glycogen consumption, increased red blood cell count, and increased efficiency of oxygen transport to muscles.
Now you may be thinking how all these benefits translate to real world results. “One study demonstrated that a 30-minute sauna session two times a week for three weeks post-workout increased the time that it took for study participants to run until exhaustion by 32% compared to baseline.” (1)
Sauna not only improves endurance but muscle hypertrophy as well. What determines whether your muscles grow or shrink is based upon your synthesis to degradation ratio. Your body is in a constant state of balancing this ratio and trying to be in a net positive of protein synthesis. Most gym goers are obsessed with increased protein synthesis but you can only do so much there. The key is decreasing protein degradation and that is where the sauna comes in to improve hypertrophy and results in a net positive protein synthesis. The mechanisms that induce decreased degradation are heat shock proteins, increase in growth hormone, and improved insulin sensitivity.
Resistance training alone increases protein synthesis however it also increases degradation due to oxidative stress via your energy producing pathways. This is a major cause of protein degradation that a majority of people don't even consider. Therefore you want to reduce degradation via the oxidative stress while holding on to the protein synthesis from lifting. This is where heat shock proteins really shine collecting those free radicals produced in your body. Again trying to look at this in a practical standpoint a “30-minute intermittent hyperthermic treatment at 41°C in rats induced a robust expression of heat shock proteins in muscle and, importantly, this correlated with 30% more muscle regrowth than a control group during the seven days subsequent to a week of immobilization.” (2)
Another benefit I mentioned is the huge increase in growth hormone. This hormone works by increasing IGF-1 synthesis which works in a couple of ways to promote skeletal muscle growth. Research on it shows “growth hormone administration to endurance athletes for four weeks has been shown to decrease muscle protein oxidation and degradation by 50%.” (3) Now administering growth hormone is expensive and therefore not very feasible for the average person and illegal to do so in most sports leagues. However you can naturally raise your levels via sauna use which is very underrated in a hypertrophy training program.
The last benefit is that it increases insulin sensitivity which is so crucial. Diabetes is the 5th leading cause in the world and is chronic disease that affects 200 million people. Treatment for diabetes pretty much starts and ends with taking exogenous insulin to deal with the issue. Your lucky if your standard primary physician gets you on any kind of diet to treat your condition and unheard of to prescribe sauna treatment. Now don’t take this as a “magic pill” that will cure you of diabetes but rather a piece of the puzzle in helping reverse the condition.
Now that we all know the physiological benefits of the sauna we can now consider how else we can utilize it outside of regular training. One is in rehabilitation after surgery or an injury. When injured you are not able to train and therefore not able to increase protein synthesis so you have to limit atrophy via decreasing degradation. Sauna is a great way to do so because all you have to do is sit there which makes it easy when injured. “Whole body hyperthermia at 41°C (105.8°F) for 30 minutes and 60 minutes attenuates hindlimb muscle atrophy during disuse by 20% and 32%, respectively.” (4,5) in rat models.
Another case where the sauna could really shine is if someone has rhabdomyolysis. You may have never heard of this because it is somewhat rare but essentially what is happening is the muscle breaking down due to overuse. When muscle tissue is broken down a byproduct is myoglobin. Excess myoglobin released into the bloodstream can cause kidney failure. Myoglobin contains protein so the heat shock proteins I brought up earlier degrade the myoglobin to the point where it is not toxic.
There are also early signs that show that heat exposure can increase longevity. “In flies and worms, a brief exposure to heat treatment has been shown to increase their lifespan by up to 15%” (6-8). Now this has only been shown in very simple creatures however because of the mechanism that boosts the expression of heat shock proteins it shows longevity potential.
Another benefit of heat exposure that would be extremely good for contact sport athletes is brain health which as of the last couple of years has been a hot button topic. When injury to the brain occurs whether it is traumatic injury, stroke or epileptic the body increases HSP production. Since your body naturally starts to increase production we could help stimulate that with sauna use and therefore help promote brain healing.
Hormone manipulation is another interesting factor considering “Study demonstrated that men that stayed in the sauna that was heated to 80°C (176°F) until subjective exhaustion increased norepinephrine by 310%, had a 10-fold increase in prolactin, and actually modestly decreased cortisol.” (9, 10). Considering men and women are very different hormonally there is “Another study, women that spent 20-minute sessions in a dry sauna twice a week had a 86% increase in norepinephrine and a 510% increase in prolactin after the session” (11) Norepinephrine is a hormone that helps with focus and attention which will help in day to day life or competing for athletes. It’s not only raising your levels immediately after use but can “Increase biological capacity to store norepinephrine for later release”(12). Prolactin promotes myelin growth which is covers nerve axons and allows for signals to move faster between the brain and muscles. This will help for anyone with a traumatic brain injury and could possibly slow down the progression of multiple sclerosis.
The final amazing benefit of heat induction has shown to increase the expression of brain-derived neurotrophic factor (BDNF). Exercise plus heat induction increases BDNF more so than just exercise alone. BDNF is important because it increases the growth of new brain cells and repairs existing ones. This could result in improved long-term memory, enhance learning potential, reduce anxiety and depression from stressful life situations. Applications of this for learning for everyone is amazing but also to possibly slow the the process of degenerative brain disorders such as alzheimer's and dementia could be possible too.
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