Sauna before or after a workout? After, and what the studies actually measured

The question is usually asked as if both answers were equal and it came down to taste. They are not equal. One order has been studied, with numbers, and it is the one where the sauna comes last. The other order has a mechanism against it that physiologists measured decades ago. Neither has the evidence the marketing implies, and the gap between the two is worth knowing before you build a habit around it.

Sauna before or after a workout: the short version

Benefits of sauna after a workout: what the studies measured

Two research groups put trained athletes in a hot sauna straight after their normal training and measured what changed. Both found the same thing first: more blood plasma.

• Scoon and colleagues (Journal of Science and Medicine in Sport, 2007): six male distance runners, a crossover design with a three-week sauna block and a three-week control block. In the sauna block they sat in a humid sauna at 89.9°C (194°F) for about 31 minutes straight after training, roughly 13 times in three weeks. Plasma volume rose 7.1% relative to control, and time to exhaustion on a treadmill at their best 5 km pace rose 32%, which the authors estimate is worth about 1.9% in a time trial.
• Stanley and colleagues (European Journal of Applied Physiology, 2015): seven well-trained male cyclists, 30 minutes at 87°C (189°F) and 11% relative humidity after training on ten consecutive days. Plasma volume peaked after just four sessions, 17.8% above baseline. Resting heart rate on waking fell; the study did not measure race performance.

More plasma is the same adaptation athletes chase with heat camps before a hot race: a bigger blood volume lets the heart fill more per beat and leaves more to send to the skin for cooling. Doing it in a sauna after training fits it into a week that already exists, which is why the practice spread through endurance sport.

Read the numbers for what they are. A 32% gain in time to exhaustion sounds like a different athlete, but a run-to-exhaustion test magnifies small changes in fitness, which is why the authors translated it into a 1.9% time-trial estimate. Six runners is a sample in which one unusual responder moves the average. And both studies measured the effect within about a week of the last session, so how long it lasts once you stop is not something they can tell you.

What has not been shown is faster recovery. Mero and colleagues (SpringerPlus, 2015) had ten physically active men do either a 60-minute hypertrophy session or a maximal endurance session, followed by 30 minutes in a far-infrared cabin, a traditional cabin, or no sauna. After the strength session, the infrared sauna changed nothing against no sauna on any recovery measure: bench press, leg press, jump height, blood lactate. After the endurance session, jump height 30 minutes later was slightly higher after the infrared cabin, 0.34 m against 0.32 m. Both cabins ran at only 35 to 50°C (95 to 122°F), far cooler than a home sauna, so the study says little about a 175°F room either way.

Why a sauna before a workout works against you

The clearest evidence is old and was not about saunas. González-Alonso and colleagues (Journal of Applied Physiology, 1999) pre-cooled or pre-warmed seven trained cyclists in water to three starting core temperatures, about 36, 37 and 38°C (97, 99 and 101°F), then had them ride in 40°C (104°F) heat until they could not continue. Every rider stopped at the same core temperature, about 40.1 to 40.2°C (about 104°F). What changed was how long it took to get there: 63 minutes from the coolest start, 46 from the middle, 28 from the warmest.

A sauna before training is a way of starting warm. You arrive at the first set or the first mile with part of your heat margin already spent, and the session ends sooner, or feels harder at the same pace. The effect is largest when the workout is long and hot, and smallest for a short lifting session in an air-conditioned gym, but it never points the other way.

The second cost is water. Our calorie and sweat-loss estimator puts a 20-minute round at 175°F at about half a litre of sweat for a 175 lb adult, and our weight-loss guide walks through the studies behind figures like it. The American College of Sports Medicine’s position stand on fluid replacement (Sawka and colleagues, 2007) puts the line where water loss starts to degrade aerobic performance at about 2% of body mass. A pre-workout sauna moves you toward that line before the session has started.

How long to sauna after a workout, and how hot

The studies above used about 30 minutes at 187 to 194°F, in trained athletes, some of them in humid heat. That is a protocol, not a starting point. For most people the conservative version is shorter and cooler, and the order matters as much as the numbers:

The temperature on the controller is read near the ceiling, not at the bench; the difference, and what the ranges mean by sauna type, are in how hot a sauna should be. For time by temperature outside a workout, see how long to stay in a sauna.

Sauna after lifting: does it affect muscle growth?

On the evidence we found, no in either direction. No trial has shown that heat after lifting adds muscle, and none has shown it takes muscle away. That distinguishes it from cold water, which has been tested and does cost you: in Roberts and colleagues (Journal of Physiology, 2015), ten minutes of cold-water immersion at 50°F after each lifting session for 12 weeks produced smaller gains in strength and muscle mass than active recovery. If you lift for size and want something after the session, the sauna is the one without a measured cost. The cold-water studies are laid out in cold plunge benefits.

Sauna or cold plunge after a workout?

If the goal is muscle growth, the sauna, for the reason above, or a cold plunge on a different day. If the goal is to feel fresher for a session in the next day or two, the soreness evidence is on the cold side, and the plasma-volume evidence is on the hot side, so it comes down to what you are training for. Doing both in a row is a different practice with its own order and its own risks, covered in sauna or cold plunge first.

What we have not measured

Everything on this page comes from published studies and from our own arithmetic, not from a bench. Two measurements are owed, and both are cheap enough that we have no excuse not to run them:

• Sweat loss per post-workout round. A bathroom scale before and after a 15-minute round at 165°F straight after a training session, against the same round on a rest day, with fluid intake logged. That replaces the estimator’s half a litre with a figure that includes the session’s head start.
• Heart rate through the routine. A chest strap through the cool-down, the round and ten minutes after, at the same temperature on a training day and a rest day. That would show how much of the “it feels harder after training” is heart rate, and how long the cool-down needs to be before it settles.

Neither replaces a trial. They would at least put a number from a real room beside the numbers from a lab.