Reviewed by Emily Carter, MSc, RD
Registered Dietitian & Hydration Research Specialist. Emily holds a Master of Science in Human Nutrition and has spent over a decade translating nutrition research into practical, evidence-based guidance for everyday health and athletic performance.
Quick answer: Regular sauna use improves athletic performance through three primary mechanisms — increased plasma volume (improving endurance by 3–5%), elevated growth hormone output (supporting muscle growth and recovery), and enhanced heat acclimation (improving performance in warm conditions). The research is clear: sauna is a legitimate performance tool, not a recovery luxury.
Why Elite Athletes Use Sauna
Distance runners, cyclists, CrossFit athletes, and strength athletes across multiple disciplines have added regular sauna sessions to their training programmes. This is not trend-following. The performance research has been strong enough for long enough that sports scientists now treat sauna as a trainable stimulus — an adaptation driver in its own right, not just a relaxation tool.
The mechanisms are distinct from exercise. Sauna applies heat stress to a body at rest, triggering cardiovascular, hormonal, and cellular responses that complement — and in some cases exceed — what training alone produces. Understanding exactly how these mechanisms work tells you how to use sauna to build a genuine competitive edge.
Mechanism 1: Plasma Volume Expansion
The most well-documented performance benefit of regular sauna use is plasma volume expansion. Plasma — the fluid component of blood — increases with repeated heat exposure as the body adapts to the cardiovascular demands of temperature regulation. (see MXR shaker) More plasma means more blood volume, which improves oxygen delivery to working muscles. Use our sauna hydration calculator to personalise your fluid intake.
A landmark study by Scoon et al. (Journal of Science and Medicine in Sport, 2007) found that distance runners who completed 30-minute post-workout sauna sessions for three weeks increased their time to exhaustion on a treadmill test by 32% compared to controls. Plasma volume increased by 7.1%. The researchers concluded that sauna-induced plasma volume expansion is a meaningful, trainable adaptation — comparable in mechanism to altitude training but accessible at ground level.
For endurance athletes, this is significant. A 5–7% increase in plasma volume translates directly to improved VO2 max, better lactate clearance, and sustained performance at higher intensities over longer durations.
Mechanism 2: Growth Hormone Elevation
Sauna is one of the most effective non-pharmacological triggers of growth hormone release. Research by Leppäluoto et al. found that two 20-minute sauna sessions separated by a 30-minute cooling period elevated growth hormone by up to 200% above baseline. Higher-frequency sauna use over multiple weeks produced sustained elevations.
Growth hormone drives protein synthesis, supports fat oxidation, and accelerates tissue repair between training sessions. For strength athletes and bodybuilders, the post-workout sauna session creates a hormonal environment that amplifies the recovery stimulus from training. For endurance athletes, it supports the repair of microdamage from high-volume training weeks.
Mechanism 3: Heat Acclimation
Athletes competing in warm or hot conditions benefit from heat acclimation — the body's adaptation to elevated core temperatures that reduces physiological strain during hot-weather performance. Traditional heat acclimation requires training in the heat, which is difficult to arrange and hard to control. Sauna achieves the same adaptation more conveniently and with less mechanical load on the body.
Regular sauna use produces: lower heart rate at a given workload in the heat, improved sweat rate and efficiency, earlier onset of sweating (reducing core temperature rise), and reduced perceived exertion in warm conditions. For marathoners, triathletes, and anyone competing in summer races, a 3–4 week pre-event sauna protocol produces meaningful performance improvements in hot conditions.
Mechanism 4: Cardiovascular Adaptation
The cardiovascular adaptations from regular sauna use — documented extensively in the Finnish cohort research by Laukkanen et al. (JAMA Internal Medicine, 2015) — include improved arterial compliance, lower resting heart rate, and increased cardiac output capacity. These are the same adaptations produced by aerobic training, which is why some researchers describe regular sauna use as "passive cardiovascular exercise."
For athletes already doing high training volumes, sauna provides additional cardiovascular stimulus without adding mechanical load — reducing injury risk while increasing total adaptation stimulus. This is particularly valuable during taper periods when training volume drops but the athlete wants to maintain cardiovascular readiness.
The Performance Protocol
For Endurance Performance (Plasma Volume + Heat Acclimation)
- Frequency: 3–5 sessions per week for 3–4 weeks pre-competition
- Timing: Post-workout (within 30 minutes of finishing training)
- Duration: 20–30 minutes per session at 80–100°C
- Rounds: 1–2 rounds with 10-minute cooling between
- Start this protocol 4 weeks before your target event
For Strength and Recovery (Growth Hormone + Muscle Repair)
- Frequency: 3–4 sessions per week, year-round
- Timing: Post-workout, after your cool-down
- Duration: Two 20-minute rounds with 30-minute cooling between
- The two-round protocol specifically maximises growth hormone output
What Not to Do: Pre-Workout Sauna
Sauna before training compromises performance. Heat stress elevates heart rate, depletes fluid, and increases core temperature — all of which reduce the quality of the subsequent training session. The research is consistent: sauna belongs after training, not before, when the goal is performance enhancement. For the full breakdown of timing, see our article on sauna before or after workout.
The Hydration Requirement
Every performance benefit above depends on adequate hydration. Plasma volume expansion is impossible if you are chronically dehydrated — your body cannot expand plasma volume when it is in fluid deficit. Growth hormone elevation is blunted by dehydration. Heat acclimation adaptations require the body to operate efficiently under heat stress, which dehydration undermines.
A 20–30 minute post-workout sauna session produces 400–600ml of additional sweat loss on top of whatever you lost during training. That is significant. Most athletes exit training already somewhat dehydrated, then enter the sauna and lose another 500ml. Without deliberate rehydration between training and the sauna, and again after the sauna, you accumulate a deficit that builds across training days.
The practical solution: the Mammoth Mug 2.5L covers your full post-workout and post-sauna rehydration in one vessel. Fill it before training, drink during the cool-down, continue through the sauna session and after. For the complete sauna hydration protocol, see our guide on sauna dehydration and our resource on hydration and recovery.
Who Benefits Most
| Athlete Type | Primary Benefit | Recommended Protocol |
|---|---|---|
| Endurance (runners, cyclists, triathletes) | Plasma volume expansion, heat acclimation | Post-workout, 3–5x/week, 3–4 week pre-race block |
| Strength / bodybuilding | Growth hormone elevation, recovery acceleration | Post-workout, 3–4x/week, two 20-min rounds |
| Team sports (hockey, soccer, rugby) | Recovery between sessions, cardiovascular adaptation | Post-game/training, 2–3x/week |
| CrossFit / functional fitness | Recovery, heat tolerance, cardiovascular base | Post-WOD, 3–4x/week |
| Combat sports | Recovery, weight management support, cardiovascular | Post-training, 3–4x/week (avoid pre-competition cut abuse) |
- Does Sauna Help With Muscle Recovery? What the Science Shows
- Sauna Before or After Workout? What the Research Says
- 7 Sauna Health Benefits Backed by Science
- Sauna Dehydration: How Much Fluid You Lose
- Sauna Rave Toronto: NRG Event Guide
For a complete overview of sauna use, see our beginner guide to sauna.
Frequently Asked Questions
How long does it take for sauna to improve athletic performance?
Measurable performance improvements from sauna-induced plasma volume expansion and heat acclimation appear within 2–3 weeks of consistent use (3–5 sessions per week). The Scoon et al. study showed significant time-to-exhaustion improvements after just three weeks of post-workout sauna sessions. Growth hormone adaptations begin after the first session and accumulate with consistent use. For the most complete performance benefit, plan a dedicated 3–4 week sauna block before your target event. See our full guide on how often to use a sauna for frequency recommendations.
Does sauna improve VO2 max?
Sauna does not directly increase VO2 max, but the plasma volume expansion it produces improves oxygen delivery efficiency — which translates to better performance at VO2 max intensity and improved lactate threshold. The 32% time-to-exhaustion improvement in the Scoon study correlates to a meaningful functional VO2 max improvement even without a direct VO2 max increase on lab tests. Combine sauna with structured endurance training for maximum effect.
Should I sauna before or after training?
After, without exception if performance is your goal. Pre-workout sauna elevates heart rate, depletes fluid, and raises core temperature in ways that reduce training quality. Post-workout sauna amplifies the recovery and adaptation signals from training without competing with the training stimulus itself. Full timing analysis in our sauna before or after workout guide.
Can sauna replace active recovery days?
Sauna complements active recovery but does not replace it. The cardiovascular and hormonal stimulus of a sauna session is meaningful — it is not complete rest. On true rest days, sauna can be used as the primary activity. On active recovery days (light movement, mobility work), sauna adds a useful additional recovery stimulus. Avoid intense sauna sessions the day before hard training efforts when you need to be fully recovered.
How much water should athletes drink before and after sauna?
Athletes face a compounded hydration challenge: training fluid loss plus sauna fluid loss. Drink 500ml in the 30 minutes before your sauna session (on top of training rehydration), 300–400ml between rounds, and 750ml–1L in the 30 minutes after your final round. Add electrolytes for any combined training-plus-sauna session exceeding 90 minutes total. Full protocol in our sauna dehydration guide.
Does sauna use increase red blood cell production like altitude training?
Yes — heat acclimation through regular sauna use stimulates erythropoietin (EPO) production, the same hormone triggered by altitude training. A study published in the Journal of Science and Medicine in Sport found that post-exercise sauna bathing (30 minutes, 3 weeks) increased plasma volume by 7.1% and improved time-to-exhaustion by 32% in distance runners. The mechanism is similar but not identical to altitude: heat stress increases blood plasma volume first, then red blood cell mass follows over 2–4 weeks.
How soon before a competition should athletes stop sauna training?
Maintain sauna sessions up to 48 hours before competition, then stop. The plasma volume and thermoregulatory adaptations persist for 7–14 days after cessation, so you retain the benefits without the acute fatigue that a sauna session can cause. During a taper phase, reduce session duration by 50% rather than stopping abruptly. The worst timing is a full sauna session the night before competition — residual dehydration and sleep disruption from elevated core temperature can impair race-day performance.
Is infrared sauna as effective as traditional sauna for athletic performance gains?
Traditional Finnish sauna (80–100°C) produces a stronger cardiovascular and thermoregulatory stimulus than infrared (50–65°C), making it more effective for the specific adaptations athletes seek — plasma volume expansion, heat shock protein production, and EPO stimulation. Infrared sauna still provides recovery benefits (reduced muscle soreness, improved blood flow) but the performance-enhancing heat acclimation effect requires core body temperature to rise above 38.5°C, which traditional saunas achieve faster and more reliably.
