Last week I wrote about a prior experience with contrast therapy. While it seemed to speed up my recovery from a couple of hard days on Grand Teton—and I’d willingly do it again in specific situations—I’d generally still take heat alone over cold any day.
As it stands, most days I do!
I’ve had infrared (IR) saunas at TNT for over a decade. I bought them because I thought they’d make a nice membership perk and, of course, for selfish reasons. Though the marketing around them leaned heavily on “detoxification”—sweating out heavy metals, BPA, and whatever else has been accumulating—I was skeptical. But I bought them anyway because I really like being warm.
Over the years, I’ve used them fairly consistently a few times per week—slightly less, but still regularly, during the summer—and I’ve come to observe a few things:
- A short (10-minute) session before training makes my body feel better during both warm-ups and my main training, especially any time the outside temp is less than 70 degrees.
- Regular year-round use seems to help me tolerate summer heat and humidity better than I did in the past.
- A medium (20–30-minute) session the day after hard training (lifting or BJJ) noticeably leaves my muscles looser and joints less achy.
Researching and writing last week’s tip got me wondering how much of this is real physiology and how much is warmth just feeling good—so I went looking to find out.
The research case for saunas
The most compelling long-term evidence on sauna use comes from Finnish researcher Tanjaniina Laukkanen, who followed more than 2,300 middle-aged men for roughly 20 years. The headline finding: compared to men who used the sauna once a week, those who used it four to seven times per week had a 50% lower risk of fatal cardiovascular events and a 63% lower risk of sudden cardiac death. A separate analysis from the same cohort found a 66% lower risk of dementia in high-frequency users—an association the researchers called significant but whose mechanism they described as “poorly understood.” A 2018 follow-up extended the cardiovascular findings to women as well, with consistent results.
Those are striking numbers, but they’re also worth contextualizing here.
These studies followed people using traditional Finnish saunas running 175–212°F. My infrared units max out at 140°F—a meaningful difference in ambient temperature, though not necessarily in physiological effect. Infrared heats body tissue directly rather than heating the surrounding air, which means a similar core temperature response may occur at lower ambient temps. Shorter-term infrared studies show directionally consistent results for cardiovascular health and recovery. But the long-term mortality data comes from traditional sauna users, not infrared.
For now, the research seems to indicate that the core mechanism—passive elevation of body temperature—is likely shared, although more research needs to be done to confirm (or refute) any long-term cardiovascular or dementia effects.
What about IR saunas?
While proof of the long-term benefits of IR sauna use for the heart and brain is still out, research does seem to back up the effects that I’ve noticed.
Heat does two things that explain what I’ve observed in the gym. First, it causes blood vessels to widen, improving circulation to muscles, tendons, and connective tissue—more oxygen in and more efficient clearance of what’s left over from yesterday’s training. Second, it reduces stiffness in those same tissues, making them more pliable and less resistant to loading. Both effects matter in practice: a short sauna session before a cold-morning workout takes the edge off; a longer one the day after hard training (lifting or BJJ) helps muscles feel looser and joints less achy. A 2023 randomized trial confirmed this—post-exercise IR sessions improved recovery and reduced muscle soreness more than passive rest.
My summer heat tolerance observation turns out to be the best-supported of the three. Regular heat exposure—from sauna, hot water immersion, or training in heat—expands blood plasma volume, making the heart more efficient and reducing the cardiovascular strain of working in hot (or, actually, any) conditions. Resting core temperature drops, sweating kicks in earlier, and perceived heat stress decreases. Year-round use plausibly maintains this baseline advantage heading into summer.
What the research doesn’t support
As I mentioned above, a common marketing claim for infrared saunas is that they “detoxify” the body by causing it to sweat out heavy metals, BPA, and other contaminants. Unfortunately, the studies cited for these claims used flawed collection methods and were too small to draw meaningful conclusions. (In one, BPA showed up in 340 out of 386 urine samples but only 3 sweat patches—indicating that the kidneys are doing more detoxification work than the sweat glands.)
Specifically, in a 2019 letter to the editors of Mayo Clinic Proceedings, Finnish researcher Jari Laukkanen—a sauna proponent and one of the co-authors of the research demonstrating the positive cardiovascular and dementia benefits (plus numerous other studies)—wrote that “the liver and kidneys usually remove more toxins than sweat glands” and declined to endorse sauna bathing as a meaningful detoxification tool. Reviewing the claim again as recently as 2024, his position hadn’t changed.
So while the detoxification claim sounds enticing, it’s not actually accurate—although the proven benefits are fortunately compelling enough on their own.
Putting it into practice
If you have access to a sauna†—infrared or traditional—here are a few practical suggestions:
- For day-after recovery from training, 15–20 minutes is the window most of the relevant research has used. More than that starts to compete with recovery rather than support it. Hydrate well before and after.
- For pre-training warm-up in cold conditions, shorter works better: 8–12 minutes is enough to take the edge off without generating meaningful fatigue before you train.
- For heat acclimation, consistency matters more than session length. Two or three sessions per week, sustained over several months, is what plausibly maintains thermoregulatory adaptations. If you’re acclimating for a specific event or trip to a hot climate, more concentrated exposure—daily or near-daily sessions over 10–14 days—accelerates the process.
If you don’t have access to a sauna, a hot bath achieves a similar passive core temperature elevation. The evidence isn’t as deep as the sauna literature, but the core mechanism is the same.