Sauna and Hot Tub Training: The Poor Man’s Altitude Training for Endurance Athletes
Every endurance athlete has heard about altitude training. Sleep in the mountains, boost red blood cells, come back faster. Sounds great until you look at the price tag for altitude tents, mountain camps, or trips to Colorado.
But there’s another performance tool hiding in plain sight: your sauna and hot tub.
Researchers are increasingly finding that repeated heat exposure creates some of the same physiological adaptations endurance athletes chase at altitude including increased plasma volume, improved cardiovascular efficiency, lower heart rate, and possibly even increased red blood cell production over time.
No, sitting in a sauna won’t magically turn you into a Tour de France rider. But for runners, cyclists, triathletes, skiers, and HYROX athletes, heat exposure may be the closest thing to “budget altitude training” available.
Why Altitude Training Works in the First Place
Altitude training improves endurance mainly because the body adapts to reduced oxygen availability.
When oxygen drops, your body responds by:
- Producing more erythropoietin (EPO)
- Increasing red blood cell production
- Expanding blood volume
- Improving oxygen delivery to muscles
The result: better endurance performance once you return to sea level.
The problem? Real altitude training is expensive, inconvenient, and hard to sustain.
That’s where heat comes in.
Heat Stress Mimics Some Altitude Adaptations
Repeated sauna or hot tub exposure creates a controlled stress response.
“Whoa, we’re overheating. We need more cooling capacity.”
So the body adapts by expanding plasma volume...the liquid portion of your blood.
More plasma volume means:
- Greater stroke volume
- Lower heart rate at a given pace
- Better thermoregulation
- Improved endurance capacity
One review on passive heat acclimation found average plasma volume increases of roughly 11% following repeated heat exposure protocols.
The Famous Sauna Study Every Runner Should Know
In one of the best-known studies, competitive runners added post-workout sauna sessions for three weeks.
The result?
- 32% improvement in time-to-exhaustion
- 7.1% increase in plasma volume
- 3.5% increase in red cell volume
- Significant increase in total blood volume
Researchers concluded sauna bathing likely improved endurance performance through expanded blood volume.
Why More Blood Volume Matters
Think of plasma volume like adding a bigger radiator to your engine.
When blood volume increases:
- Your heart pumps more efficiently
- You maintain pace with less cardiovascular strain
- Cooling improves
- Oxygen transport improves
- Recovery between intervals improves
Athletes often notice:
- Lower heart rate during easy runs
- Better heat tolerance
- Less perceived exertion
- Stronger finishing kick late in races
A 2015 cycling study found post-exercise sauna use expanded plasma volume by nearly 18% after only four heat exposures.
Can Heat Exposure Increase Red Blood Cells Too?
For years, scientists believed heat training only increased plasma volume.
Newer research suggests repeated heat exposure may indirectly stimulate erythropoiesis (red blood cell production), similar to altitude training.
Proposed mechanism:
- Heat expands plasma volume
- Blood becomes temporarily diluted
- The kidneys detect lower red blood cell concentration
- EPO signaling may increase
- The body gradually increases red blood cell production
Researchers are actively studying this relationship.
Why Hot Tubs Work Too
No sauna? No problem.
Hot tubs can create similar adaptations if the water temperature and duration are high enough.
The key is raising core body temperature consistently.
Your body responds similarly whether heat comes from:
- Finnish sauna
- Infrared sauna
- Hot bath
- Hot tub
- Steam room
The Hidden Advantage: Better Heat Tolerance
Most endurance races are not held in perfect weather.
Heat acclimation can improve:
- Sweat response
- Thermoregulation
- Cardiovascular stability
- Perceived effort in hot conditions
Elite athletes have used heat adaptation strategies for decades because overheating destroys performance long before fitness does.
How to Use Sauna Training Properly
Basic Endurance Sauna Protocol
Immediately after training:
- 20–30 minutes in the sauna
- 3–5 times weekly
- 175–190°F (79–88°C) for dry sauna
- Hydrate aggressively afterward
For hot tubs:
- 20–40 minutes
- 102–104°F (39–40°C) water temperature
Consistency matters more than extreme sessions.
Important Safety Considerations
Heat training is still stress. Done poorly, it can hurt recovery instead of helping.
Avoid sauna sessions when:
- Severely dehydrated
- Sick
- Sleep deprived
- Hungover
- Overtrained
If you feel dizzy, nauseous, or lightheaded, exit immediately.
Is Sauna Training Better Than Altitude Training?
Not exactly.
Altitude training primarily improves oxygen-carrying capacity through hypoxia.
Heat training primarily improves cardiovascular efficiency through plasma expansion and thermoregulation.
But the overlap is significant enough that many physiologists now view sauna training as one of the most practical endurance performance tools available.
Final Thoughts
Performance breakthroughs are often surprisingly simple.
Not expensive gadgets. Not miracle supplements. Not altitude tents.
Sometimes it’s just sitting in a hot wooden box after training.
The evidence continues to grow that regular sauna and hot tub exposure can:
- Expand plasma volume
- Improve cardiovascular efficiency
- Reduce heart strain
- Improve heat tolerance
- Potentially support red blood cell adaptations
For endurance athletes, that makes heat exposure one of the highest ROI recovery and performance tools available.
