Instalab ResearchAt its essence, the sauna is controlled stress. The air inside, often above 80°C in Finnish saunas, forces the body to adapt. Heart rate climbs, vessels dilate, and blood flow to the skin and muscles increases dramatically. For athletes, this response mimics moderate exercise itself: the heart works harder, sweating accelerates fluid loss, and the body practices thermoregulation. Repeated exposure leads to what exercise scientists call “heat acclimation,” a process that improves plasma volume, cardiovascular stability, and even endurance performance.
Infrared saunas, which operate at lower temperatures but penetrate heat more deeply into muscle tissue, act somewhat differently. They raise core temperature gently, with less strain on the cardiovascular system, and are often used for relaxation and recovery. Mist or steam saunas, on the other hand, emphasize humidity, heightening heat transfer and sweat loss.
So does it make sense to heat up before you work out, or after?
Some athletes use the sauna before exercise to loosen stiff muscles or raise core temperature. In one controlled study, individuals who spent time in a Finnish sauna before moderate aerobic exercise experienced smaller increases in blood pressure during the workout compared to exercising cold. This suggests a mild cardiovascular preconditioning effect, where blood vessels are already relaxed and responsive, allowing smoother circulation.
However, there’s a catch. The same exposure also slightly elevated resting heart rate and perceived exertion during exercise, essentially making the workout feel harder. The body was already partially under heat stress before it began training. This isn’t necessarily bad for low-intensity sessions, but it could limit performance in high-intensity work or competitions.
In short, pre-exercise sauna use seems to relax the vascular system but may increase cardiovascular strain if overdone. It’s like stretching your engine before a race: helpful for the system, but risky if you push too hard too soon.
The bulk of scientific evidence favors sauna use after exercise, particularly for endurance athletes. Post-exercise heat exposure appears to amplify cardiovascular adaptations and help muscles recover more effectively.
A landmark trial with trained runners found that three weeks of post-exercise sauna bathing improved aerobic capacity and running economy, likely by expanding plasma and red-cell volume, which effectively enhances the body’s oxygen transport system. Later studies confirmed these results in both hot and temperate conditions, showing that adding sauna sessions after workouts improves heat tolerance and modestly boosts VO₂max, the gold-standard measure of endurance fitness.
For athletes training in diverse climates, this effect matters. Sauna use mimics heat training without requiring outdoor exposure, conditioning the body for better thermal efficiency and circulation. The result: a slower heart rate at the same intensity, less perceived exertion, and better tolerance to environmental stressors.
But endurance isn’t the only beneficiary. A 2022 study found that a single infrared sauna session after resistance exercise reduced muscle soreness and improved recovery of explosive power within 24 hours. Another trial extended sauna use across six weeks and found that while it didn’t increase muscle hypertrophy, it appeared to enhance long-term power output capacity, suggesting subtle neuromuscular benefits.
This pattern of enhanced recovery and modest performance gains echoes across various modalities. Sauna bathing appears to accelerate cardiovascular and neuromuscular recovery without directly amplifying muscle growth. In plain terms, it helps you bounce back faster, not necessarily build more.
Not all research paints heat as heroic. A 2019 experiment on competitive swimmers found that those who used the sauna immediately after intense training actually performed worse the next day, showing slower sprint times and greater fatigue compared to passive rest.
Why? Likely because the combination of exercise-induced and heat-induced stress pushed their recovery systems past optimal limits. The body perceives both as physiological stressors, each triggering inflammation, hormonal responses, and fluid loss. Stack them too close together, and you risk compounding fatigue rather than relieving it.
This “overheating paradox” is well-documented. In earlier studies, endurance athletes who used the sauna too soon after maximal efforts saw temporary declines in performance, particularly within 24 to 48 hours. The takeaway isn’t to avoid the sauna, but to time it wisely, using it for longer-term adaptation rather than acute recovery before a major competition.
The benefits of sauna extend beyond muscles and lungs. On the biochemical level, heat exposure influences oxidative stress, inflammation, and cellular repair. A study on healthy men showed that post-exercise Finnish sauna sessions reduced markers of oxidative stress in red blood cells while boosting antioxidant enzyme activity, suggesting an adaptive hormetic effect, where mild stress strengthens future resilience.
However, not all systems respond equally. Research on gut health found that four weeks of post-exercise sauna use did not significantly alter gut microbiota or inflammatory markers in healthy men, indicating that moderate sauna exposure doesn’t appear to disrupt intestinal balance.
Meanwhile, chronic sauna users show lower systemic inflammation overall, as indicated by reduced C-reactive protein levels—a finding that supports sauna’s long-term cardiovascular protective role.
The science suggests that sauna timing should align with the goal of the session. Before training, short heat exposure may be used as a cardiovascular primer, but it’s not optimal for performance-heavy workouts. After exercise, sauna use can enhance cardiovascular adaptation and aid recovery, provided hydration and rest are adequate.
Infrared saunas may hold a unique edge for post-training use. Because they heat more gently, they seem to reduce soreness and fatigue without provoking the heavy cardiovascular stress of traditional Finnish saunas. This makes them especially useful between closely spaced workouts or in strength-dominant sports where overheating could impair muscle function.
Duration and frequency also matter. Most studies showing performance benefits used sessions around 20 to 30 minutes at 80 to 100°C, three to four times per week, for several weeks. Sporadic use likely helps relaxation but won’t drive lasting adaptation.
In the end, the science leans firmly toward after. Sauna bathing is most beneficial when used as a post-exercise recovery tool or adaptation enhancer, not as a warm-up ritual. Heat exposure after training amplifies cardiovascular resilience, may ease muscle soreness, and nudges the body toward better thermoregulation. Pre-exercise use can serve as gentle preparation, but for most, it’s a mild luxury rather than a performance booster.
The sauna, like training itself, is about controlled stress. Use it too aggressively or too often, and it becomes another source of fatigue. But applied strategically, after hard work, with rest and hydration, it becomes what ancient Finns always claimed it was: a place not just for sweating, but for transformation.
