Sauna Before or After a Workout?

After. For nearly every goal that brings people through the door — recovery, cardio, sleep, feeling human again — the sauna belongs at the end of your session, not the front of it.

The before case isn't zero. It's just narrow: a few minutes, low intensity, as a loosener. Long and hot before you lift is the version that backfires, and there's a mechanism for why.

There's also a part nobody in this industry wants to say out loud. The evidence that cold immersion blunts muscle growth is real, and it points straight at our own plunges. We'll get to that.

Start with the study everyone quotes. Six male distance runners, sauna at about 90°C for roughly 31 minutes immediately after training, around 13 sessions across three weeks. Run time to exhaustion went up 32%. That's the number that ends up in every headline.

The authors themselves deflate it. Time-to-exhaustion is a test format that exaggerates, and translated into an actual endurance time trial they put the improvement at about 1.9%. Real. Also a rounding error next to "32%."

The mechanism is the more useful finding. Plasma volume rose 7.1% over those three weeks — more plasma means more stroke volume, better cooling, easier work at the same pace. Red-cell volume rose 3.5% as well, but that interval ran from −0.8% to 8.1%, so treat it as unproven. Six men, incidentally. Hold that thought for the rest of the page.

A better-built trial backs the direction. Twenty trained middle-distance runners, 13 of them women — which almost never happens in this literature — sat in a 101–108°C sauna for 28 minutes, three times a week, entering within about five minutes of finishing outdoor training. Over three weeks the sauna group improved VO2max by about 8%, time to exhaustion by 12%, and speed at 4 mmol/L lactate by 4%. The control group went nowhere on all three, which is what makes those numbers worth anything — though the spread on the VO2max figure was wider than the effect itself, so the group average is hiding a lot of individual scatter.

Then the part that may matter most here. In a 40°C heat tolerance test, the sauna group finished 0.3°C cooler in the core, and ran 11 bpm lower in heart rate and 0.8°C cooler at the skin than control. That cluster is heat acclimation, and if you race a Charlotte July it may be the most valuable thing on this page. Worth knowing: stretching the protocol from three weeks to seven added almost nothing, and only six people did the extension. The adaptation front-loads.

Heat makes you weaker. The cleanest evidence is a lab study of seven people doing elbow-flexor contractions after being passively heated to roughly 38.5°C core. Brief maximal efforts dropped 2.4%. Sustained two-minute efforts dropped 12%. Where it broke is the interesting bit, and it broke in two places at once: voluntary drive faltered at or above the motor cortex, while the muscle's own contractile properties sped up enough that the drive couldn't keep pace with them. The paper's title says it plainly — a failure of the motor cortex and the muscle.

Be honest about what that is, though. Seven subjects, one small muscle group, a heating protocol that is not a sauna. Nobody has run "sauna before squats versus no sauna" as a proper trial. The mechanism is well characterized and points one direction; the applied claim is an extrapolation and we'll label it as one rather than dress it up.

So when does before make sense? Short and light. Five minutes to loosen a stiff back before mobility work or an easy zone-2 spin. Not a full round. Not löyly. Not sweating through a towel and then walking to a barbell. Our take: skip it. A warm-up that looks like the thing you're about to do beats heat every time, and the sauna will still be there in an hour.

Now the sober version. The most current synthesis of post-exercise heat — 14 studies, 194 participants, published 2025 — reads nothing like the podcast summary. For acute recovery: four studies showed benefit, four showed nothing, one showed a negative outcome. For long-term training adaptation, two of five showed improvement. Heterogeneity was bad enough that the authors couldn't run a meta-analysis at all, and they conclude flatly that definitive conclusions aren't possible.

Look at where the signal actually lives and a split appears. Endurance is where post-exercise heat looks good, specifically for running performance in hot conditions, by way of acclimation — and even there, repeated heat didn't move VO2max in the cycling tests at all. For resistance training the results are a scatter: one study found faster recovery of isometric squat strength, others found nothing, and no consistent benefit emerged. Post-run sauna has a case. Post-lift sauna mostly has a vibe.

One timing wrinkle should temper what you expect. That review found benefits were most likely immediately after the heat exposure. Retest performance the next day and effects were generally minimal or even negative. Sauna after training probably isn't buying you a better Tuesday. It might be buying you a better rest of Monday.

This is the part where the evidence cuts against the business we're in.

Twelve weeks, 21 physically active men, cold water immersion after every strength session versus active recovery. The active recovery group gained more strength and more muscle. Type II fibre cross-sectional area rose 17% and myonuclei per fibre rose 26% — in the active group only. A separate acute arm found cold blunted satellite cell responses and p70S6K signalling. That study is why your gym has an argument about ice baths.

Then it gets complicated. A 7-week trial put 16 men in 10°C water for 15 minutes after every session. Type II fibre growth was attenuated, same as before, and mTORC1 signalling was blunted at 1 hour and 48 hours. But 1-RM leg press improved about the same in both groups — no strength penalty turned up at all. Anyone telling you cold plunging kills your strength is quoting one study and ignoring the other.

The 2024 meta-analysis should be the tiebreaker and it only half-breaks it. Across 8 studies, resistance training alone produced a hypertrophy effect of 0.36; cold plus resistance training produced 0.14. The comparative effect was −0.22 with a 95% credible interval of −0.47 to 0.04, which crosses zero — though the authors still read the difference as probably real. They word it as "some evidence," not proof, and rate the underlying studies fair to poor: three fair, five poor, none good. A consistent signal pointing one way, built on weak trials. That's the honest description, and it isn't settled science.

Notice what every one of those studies had in common: cold after every single session. Nobody has tested plunging once a week, or during a deload, or the week of a race. "Never plunge after lifting" overshoots the data badly — the evidence speaks to a habit, not to a plunge.

Two distinctions get blurred constantly and both matter. The blunting evidence is about cold, not heat — it does not transfer to sauna. There's no good evidence a post-lifting sauna suppresses hypertrophy the way cold appears to, but there's also little evidence it helps, so don't read this as "use sauna instead to grow." And these trials are tiny: 21 people, 16 people, 8 studies, mostly young men, four to twelve weeks. Of the eight studies in that meta-analysis, exactly one included any women. Nobody knows what happens across a real training year.

One question none of this literature answers: whether you personally should be doing any of it. Cold water triggers a gasp reflex and a sharp spike in heart rate and blood pressure, and heat puts its own load on the cardiovascular system. If you have a heart condition, blood pressure that isn't well controlled, if you're pregnant, unwell, or you've had a drink, that's a conversation with your doctor — not something to settle from a study of 21 healthy men in their twenties.

• Hypertrophy is the goal — don't make cold-after-lifting a habit. Sauna after is fine. Plunge on rest days or after cardio.
• Endurance is the goal — sauna soon after the run. Plunge whenever you want.
• In-season, or a meet next week — recovery beats adaptation. Plunge. Feeling good on the day is the whole point.
• You just want to feel human — any order you like. This is 90 minutes of your week, not a periodization crisis.

Here's the honest answer to the most-asked version of this question: nobody has tested it. No study we can point at compared different delays between finishing training and entering the heat. If someone hands you a confident "wait 10 to 15 minutes," they invented it.

What we can say is what the working protocols did. The six-runner study went in immediately. The twenty-runner study went in within about five minutes. Both showed benefit. That's inference from how the trials were designed rather than a variable anyone tested — but if you're chasing the endurance effect, going in soon is what the evidence was actually built on. For lifting, the thing worth delaying isn't the heat. It's the cold.

Hydration deserves plain talk instead of a fake number. You sweat hard in a 90°C room, and you sweat harder if you arrive already down a liter from training. Drink before you come in, drink between rounds, use the lounge. People walking in straight from the gym often ask some version of "am I too dehydrated for this" — and the useful answer is that if you're lightheaded, cramping, or you haven't had anything to drink since your session, sit the first round out and fix that first. Otherwise: drink now rather than after, and leave when you've had enough rather than when the clock says you're done.