what does a sauna actually do for you?
short answer:
saunas mimic light to moderate exercise by raising core temperature and heart rate. the benefits from this body reaction can include; decreased muscle soreness, heightened parasympathetic nervous system activation, decreased inflammation, and improved cardiovascular health —with regular use —around 2 to 4 or more sessions per week over the long term. you can achieve the same benefits through light biking or walking, these results are not unique to sauna usage.
long answer:
saunas have been around for thousands of years with origins in northern europe, particularly finland. saunas have been used for cleansing, relaxation and spiritual practices and have evolved from simple underground pits to wooden structures you see today. there are two types of saunas, traditional finnish and infrared.
finnish saunas heat the air around you (150-195+°F) warming you from the outside in through a wood, gas or electric heater most often located under a pile of rocks. this creates a more intense environment that can be very humid, if you throw water on the heated rocks, so sessions in these types of saunas are short, usually 10 to 15 minutes.
infrared saunas are a new technology that warms the body from within through infrared light permeating skin and tissues; because of this the temperatures are much lower (110–140°F) than finnish saunas. since the air temperature’s lower than finnish saunas, the environment is much less intense (good for beginners) and sessions tend to be longer (30-45 minutes). with any new technology its natural that it’s met with some apprehension, in this case the concerns center around skin health and radiation effects. let’s check it out.
Barolet, D., Christiaens, F., & Hamblin, M. R. (2016)
when we look at the solar spectrum we have ultraviolet (UV) light on one side, which is the most studied and has been shown to have enough energy to break chemical bonds and carry out photochemical reactions —melanoma from excessive sun exposure for example. infrared light is found on the other side of the spectrum with near infrared (nir) being slightly closer to UV than far infrared (fir) light. there’s less research on infrared light but what we know is that infrared is not inherently harmful to skin — it’s effect is dependant on context and intensity.
high thermal exposure, from heat or intense artificial Infrared light can damage collagen and promote photoaging changes —changes to the skin. further, Very intense Infrared light exposure experiments showed increases in markers of oxidative stress —when reactive oxygen overwhelms your body’s antioxidant defenses, damaging cells faster than they can repair themselves— and MMP expression —enzymes crucial for normal processes like tissue repair and development, but also implicated in diseases like cancer, inflammation, and cardiovascular disorders— but these intensities far exceeded typical solar irradiance.
at appropriate doses, from the natural world and adequate time in most infrared saunas, infrared light may be able to stimulate cellular responses beneficial to skin such as, enhanced wound healing, anti-inflammatory effects, increased cell proliferation (increase in numbers) and collagen synthesis. These effects are linked to mechanisms like mitochondrial activation, reactive oxygen signaling, and gene expression pathways. low- to moderate-intensity exercise can also activate many of these same cellular pathways, promoting repair and resilience through whole-body metabolic and signaling responses.
with infrared light there is a chance to over expose yourself. to prevent overexposure double check that your, or your gyms, infrared sauna wavelength range is between 700 - 1400 nm.
now, if you want to get nitty gritty there’s some animal and in vitro studies that suggest infrared saunas between 810 - 880 nm have the greatest cellular benefits and 940 - 1060 nm support deeper healing, but really anything between 800 - 1000 nm seems to be solid. just limit sessions to 30-45 minutes max, stay hydrated, and make sure there’s proper ventilation.
the same goes for finnish saunas, stay hydrated and make sure not to stay in the sauna for too long. seriously, 10-15 minutes is plenty and will yield all the benefits you need. more is not better in this case. if you do want to accumulate a longer time in the sauna do 10-15 minutes, then cool off in a normal temperature room for 5-10 minutes, or a jump into a cold tub or shower and return to the sauna. two to three rounds of this can be a nice way to relax on an off day.
when it comes to recovery, infrared saunas have shown to be beneficial in decreasing soreness when done right after resistance training with no negative effects on one’s autonomic nervous system. this is because the effect you’re getting from a sauna mimics light exercise which increases blood flow and cellular repair signals while creating a mild, short-lived stress that the autonomic nervous system can easily compensate for —you’d get the same result if you walk or ride your bike at an easy pace. just saying.
finnish saunas help with recovery by increasing your heart rate variability which indicates heightened parasympathetic activity (rest and digest) and diminished sympathetic activity (fight or flight). this result isn’t unique to this type of sauna, when your body naturally cools itself down, from exercise or high heat, you’ll see this result —again, you’d get the same recovery benefits if you walk or ride your bike at an easy pace.
what I’m trying to get across is that you can argue about the exact mechanisms behind each sauna’s cardioprotective and recovery effects, but at the end of the day, both mimic light to moderate exercise, which is what actually produces the benefits.
the only real difference between finnish saunas and infrared saunas are how they heat you up. these are not biohacks or “cheat-codes” they’re simply vessels that mimic low to moderate intense exercise, which can be helpful for certain populations. if you can do low to moderate exercise always prioritize that over a sauna as you’ll get all the benefits mentioned above plus others not mentioned. don’t think you can just sauna instead of doing cardio. think of saunas as a cherry on top of the sundae, and consistent low to moderate exercise is the ice cream itself.
now, if you want to add the cherry on top —under the guise that you already engage in well above the recommended activity guidelines for strength training and cardio — you can add a sauna at the end of your zone 1-2 cardio sessions. this will increase your time in zone 1-2, providing additional benefits to your cardiovascular system without the added load on your muscles. an example here is 45-90 minutes of zone 1-2 training followed by 1-2 rounds of 10-15 minutes of a finnish sauna or 1 round of 30-45 minutes of an infrared sauna. if you’re looking for a recovery day, given the only other activity on this day is a light workout or nothing at all, try 2-4 rounds of 10-15 minutes of a finnish sauna followed by 10 minutes in a normal temperature room or 30 second to 3 minute cold tub. for infrared you can drop to one 45 minute sauna session followed by a 30 second to 2 minute cold tub.
again, use this as a tool but don’t ignore what’s really moving the needle — resistance training and cardio.
miles is a trainer, speaker, writer, and consultant who specializes in performance and longevity within the health and wellness space. with over ten years of experience, a masters degree in exercise and nutrition science and multiple strength and conditioning certifications miles aims to combine practical application with research to provide actionable strategies for people looking to live longer and excel athletically.
References:
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