Section F · Work, Heat & Everyday
Sauna & Cold Plunge
Twenty minutes at 180°F is a pint of sweat. Stacked after training on plain water, it drains the rest of the day.
A sauna session can cost 16 to 32 oz in twenty minutes. People stack it after a hard session, hydrate with plain water, and feel drained for the afternoon and cramp that night.
Sauna straight after a hard session with nothing in between is two workouts of sweat on one bottle of water. One stick before you go in, one after. One before, one after. Two on top of the training-day sticks. One stick in 16 oz covers a window; the schedule below covers the day.
The numbers behind sauna & cold plunge
A sauna session can cost 16 to 32 oz in twenty minutes. People stack it after a hard session, hydrate with plain water, and feel drained for the afternoon and cramp that night.
Why this happens
Sweat is not just water. Every ounce carries sodium out with it, and sodium is what lets your blood hold its volume. Lose enough and there is less blood to move oxygen to working muscle, so your heart rate climbs for the same split, your core temperature drifts up, and the nerve signal that tells a muscle to relax gets noisier. That is the cramp, the dizzy stand-up and the split that will not come back, all from the same cause.
Plain water puts the volume back without the sodium, which is why it can feel like it is not working. The fix is to put back what actually left: water and the minerals that went with it, in roughly the ratio you lost them.
In a 180°F room the air is hotter than your skin, so it is heating you while your sweat is trying to cool you. You lose fluid at a training rate while sitting still. Skin blood flow climbs to dump heat, and the volume that flow needs is exactly what the sweat is taking. That is why the lightheaded stand-up shows up on the second round, when the deficit has had time to build.
Sauna straight after a hard session with nothing in between is two workouts of sweat on one bottle of water. One stick before you go in, one after.
A pint a round, and the second round is where it bites
Sixteen to thirty-two ounces leave you in one twenty-minute round, sitting still. A second round doubles it, and for a heavy sweater that is past the 2% line before the plunge. Walk in after training and you start two pounds down, so shift the whole band up by that.
Two rounds is 32–64 oz. The 2% line (3.5 lb, 56 oz for a 175-lb athlete) sits inside the second round for a heavy sweater.
One stick before and one after put back 1,200 mg. That covers the session and the two pounds you walked in with.
What you get back when you do it right
Runners who added post-exercise sauna for three weeks carried more plasma volume and ran longer to exhaustion.
Scoon et al., J Sci Med Sport, 2007In a 20-year Finnish cohort the men who used the sauna most often had the lowest rates of fatal heart disease.
Laukkanen et al., JAMA Internal Medicine, 2015Cold water after training lowers next-day soreness. Step in on a settled heart rate and a topped-up volume and you get the reset without the dizzy spell.
Bleakley et al., Cochrane Review, 2012Seven days in, the post-sauna headache stops. Two weeks, the night cramps. A month in, longer sessions without the drain.
The Hydration PlaybookA plunge straight after lifting can blunt the muscle gains you just trained for. Put it hours later, or on conditioning days.
Roberts et al., J Physiol, 2015
Dry, then hydrated, piece by piece
The red panel is what is happening now. The green one is what the next section buys you, and roughly how long each part takes to show up.
- Already down two pounds from the session
- Plain water in the locker room, or nothing
- Core temperature still elevated from the workout
- Sweat pouring; a pint in twenty minutes
- Heart rate climbing at rest
- Lightheaded on the second round
- Dizzy stepping out or into the plunge
- Headache within an hour
- Cramps that night
What to drink, and when
Start with before. It is the window most people in sauna & cold plunge get wrong. For a normal training day rather than a race, the timing guide covers every window.
BEFORE
- 16 oz with a stick, sipped
- Especially if it follows a training session
Start full; twenty minutes takes a pint whether you brought it or not.
DURING
- Sips from a mixed bottle on the bench outside
- Not a full bottle in the heat
Keeps the deficit from opening while the core is at its hottest.
AFTER
- 20 oz with a stick
- Then dinner
Stops the headache and the night cramp.
Your number is not an average. Weigh yourself before and after one hard session and you know your sweat rate for the season.
What to take, and what we do not sell
Two of these three are things we do not sell. A hydration stick does not fix fuelling, and pretending otherwise is how people end up disappointed.
Electrolytes
Fuel
Worth taking too
The questions we get about sauna & cold plunge
How much do you sweat in sauna & cold plunge?
180°F is the room; your core climbs two degrees inside it. 16–32 oz of sweat in twenty minutes. Weigh in before and out after a session: every pound down is about 16 oz you did not put back.
When should I drink during sauna & cold plunge?
Before you walk in: 16 oz with a stick, sipped; Especially if it follows a training session. Start full; twenty minutes takes a pint whether you brought it or not.
What should I drink before sauna & cold plunge?
Before you walk in: 16 oz with a stick, sipped; Especially if it follows a training session. Start full; twenty minutes takes a pint whether you brought it or not.
How do I recover after sauna & cold plunge?
Within 30 minutes: 20 oz with a stick; Then dinner. Stops the headache and the night cramp.
Do I need electrolytes or is water enough?
Water replaces the volume you sweat out but not the sodium, potassium and magnesium that left with it, and without sodium your body cannot hold the water. Per hour of hard work: Sodium 500–700 mg, Potassium 150–300 mg, Magnesium 30–60 mg, Water 16–24 oz.
How many sticks do I need?
One before, one after. Two on top of the training-day sticks. Set the mixed bottle on the bench outside before you go in. A walk to the locker room between rounds never happens.
Should I cold plunge right after the sauna?
Heat then cold is fine when you walk into the cold on a settled heart rate. Sit on the bench first, sip the mixed bottle, and go in once your pulse has come down. Dizzy on the way in means you stepped out too dry. If the sauna followed a lifting session, put the plunge hours later or skip it that day; cold straight after lifting can blunt the gains you trained for (Roberts et al., 2015).
Is a sauna after a workout good or bad?
Good, on one condition: you replace what the workout took before you add the sauna's pint. Done that way, post-exercise sauna is one of the better-studied recovery habits (Scoon et al., 2007). Done on plain water, it is the headache and the night cramp in the red panel.
Does the cold plunge dehydrate you too?
Not the way the sauna does. Cold water pushes blood to the core and makes you need to pee, which is fluid out, and the cold blunts thirst. So the plunge adds little sweat but hides how dry you already are. The stick after covers both.
Everything in the box
The book this article came from is in there too. One page for every sport, so the next thing you take up is already covered.
Five flavours, one stick each
Taste is the only part of this you cannot take our word for. The starter kit gets you all five so you find the one you will actually reach for at minute four, not the one that sounded good online.
- All five minerals sweat costs you, no sugar.
- Informed Sport certified, batch by batch.
- Mixes into whatever bottle is already on the bench outside the sauna.
