Three weeks of post-training sauna bathing was followed by a 32% rise in treadmill run time to exhaustion in competitive male runners. Plasma volume rose 7.1% over the same period (Scoon et al., Journal of Science and Medicine in Sport, 2007, retrieved August 2026).
This guide covers what athletes and trainers do with sauna heat, and which sauna recovery benefits the peer-reviewed evidence supports. If you're new to sauna, our beginner's guide to sauna covers how to structure a first session.
Key Takeaways
- In a small study of trained runners, three weeks of post-training sauna was followed by a 32% rise in run time to exhaustion (Scoon et al., 2007). Plasma volume rose 7.1%.
- Evidence for easing next-day soreness is mixed: a 2025 review of 14 studies found four showing a benefit and four showing none.
- Cold water immersion after strength training measurably reduces muscle and strength gains. No study has found the same for sauna heat.
- Studies that found endurance gains applied the heat after training.
- Rehydration research used around 150% of the fluid lost, with sodium (Shirreffs et al., 1998).
what has research found about sauna and muscle soreness?
For soreness, the evidence is thin. A 2025 systematic review covered 14 studies and 194 participants. Four reported a benefit for delayed onset muscle soreness, four reported no effect, and one reported an adverse result (Sports Medicine – Open, 2025, retrieved August 2026).
A Bayesian network meta-analysis published in June 2025 was more favourable. Heat treatment produced significant effects on soreness against placebo within the first 48 hours after exercise, with the effect fading after that window (Journal of Pain Research, 2025, retrieved August 2026).
Protocols across those 14 studies ranged from 36°C to 105°C and 10 to 40 minutes, and the reviewers rate the underlying research as low to moderate quality. Heat may change how sore you feel in the first day or two. There isn't an agreed dose yet.
what has research found about sauna and endurance?
The endurance evidence is stronger, and researchers link it to changes in blood volume. Six competitive male runners added post-training sauna sessions for three weeks, around 31 minutes at 89.9°C, roughly 12 sessions in total. Run time to exhaustion rose 32%, which modelled out to a 1.9% improvement over 5km (Scoon et al., 2007, retrieved August 2026).
Plasma volume rose 7.1% across the same three weeks. Researchers suggest that more plasma means more blood available to move heat to the skin and oxygen to working muscle. A separate trial in well-trained cyclists used 30-minute sauna exposures at 87°C, taken immediately after training. Plasma volume peaked at 17.8% above baseline after only four of them, and waking heart rate fell about 10% (European Journal of Applied Physiology, 2015, retrieved August 2026).
There is Australian data on the same adaptation. Fifteen semi-professional Australian Rules footballers completed a six-week programme of passive hot water immersion. Intermittent running performance improved from 19.9 to 20.8 km/h, with plasma volume expansion alongside it (PLoS ONE, 2022, retrieved August 2026). That study used hot water instead of a sauna, and it produced the same plasma volume expansion.
The gains are specific. The same 2025 systematic review found no effect on VO2max or on cycling performance (Sports Medicine – Open, 2025, retrieved August 2026). The improvements researchers found were in heat tolerance and in how long participants could hold a pace.
what has research found about sauna and ice baths after training?
It depends what the training is for. Twelve weeks of post-workout cold water immersion held quadriceps muscle growth to around 2%, against roughly 15% for men doing active recovery instead. Leg press strength rose 42% against 59%. Knee extension came in at 21% against 39%, and isometric knee extensor strength at 10% against 26% (Roberts et al., The Journal of Physiology, 2015, retrieved August 2026). Every measured outcome favoured active recovery.
No study has found the same effect for sauna heat. Head-to-head trials of sauna against cold water immersion are still sparse, so the case for heat rests on what cold does to strength gains.
In that trial, cold water immersion straight after strength training was linked with smaller gains in size and strength. No study has found the same for sauna heat. Athletes still use cold water immersion when they need to feel fresh for a game the next day.
when did studies schedule sauna around training?
Every study above that found a performance benefit applied heat after the training session, usually within about 15 minutes of finishing.
One 2015 trial put the sauna first. Fifteen minutes at 76.7 to 82.2°C before eccentric exercise reduced the strength and range-of-motion deficits over the following week (Asian Journal of Sports Medicine, 2015, retrieved August 2026). That design hasn't been widely replicated.
Heat before training adds thermal and cardiovascular load before the session starts. Heat acclimation blocks before racing in hot conditions are a separate use, with their own protocols.
how much fluid do sports guidelines suggest around a sauna session?
The American College of Sports Medicine advises keeping fluid loss under 2% of body mass. Past that point, power output drops and heat illness risk climbs (American College of Sports Medicine position stand, retrieved August 2026). A sauna on top of a hard session brings you closer to that threshold.
In rehydration research, drinking around 150% of the fluid lost, with sodium, restored fluid balance (Shirreffs, Taylor, Leiper & Maughan, American Journal of Physiology, 1998, retrieved August 2026). Some of what you drink leaves as urine before it's absorbed, so matching losses one for one leaves you short.
Weigh yourself before and after a session if you want a number that applies to your body and your sauna. Our sauna aftercare routine covers the rest of that window, including how long to spread the fluid over.
| Outcome | What the research shows | Strength |
|---|---|---|
| Endurance and heat adaptation | 32% longer run time to exhaustion and 7.1% more plasma volume after three weeks | Good, on small samples |
| Delayed onset muscle soreness | Mixed. Four of 14 studies positive, four null, one adverse. Some effect inside 48 hours | Weak |
| Protecting strength and size gains | Cold water immersion measurably reduces them. No study has found the same for heat | Moderate, and indirect |
| VO2max and cycling performance | No effect found in the 2025 systematic review | Clear null result |
what protocols did the recovery studies use?
The recovery findings with evidence behind them came from repeated sessions. In the studies above, participants took the heat after training, for around 30 minutes at 87 to 90°C, over about three weeks. Some split each session across two sittings with a break between them.
Every study above was run on healthy, trained adults. If you're pregnant, or you have a heart condition, low blood pressure or a history of heat intolerance, talk to your doctor before adding sauna sessions on top of hard training.
A densely felted merino hat insulates the head from the hottest air in the room, and many people find longer sessions more comfortable with it. Our guide to the benefits of a sauna hat covers the mechanism, and why merino wool is the gold standard covers the fibre.
When we developed the FELT. hats we tested a spread of thicknesses and settled on 4mm as the practical middle: enough insulation for a long session, light enough to dry between uses. Both The Classic and The Modern use it. Airing a hat out after a session is usually all the care it needs.
For the wider setup around those sessions, see our complete guide to setting up a home sauna routine. The essential home sauna accessories checklist covers what else is worth having. Our guide to what research says about sauna use and your health covers the cardiovascular and sleep research beyond recovery.
common questions about sauna and recovery
what has research found about sauna and delayed onset muscle soreness?
The evidence is mixed. A 2025 systematic review of 14 studies found four reporting a benefit, four reporting no effect, and one reporting harm. A 2025 meta-analysis did find a significant effect against placebo within the first 48 hours after exercise. Heat may change how sore you feel in the short term, and the research base behind that is rated low to moderate quality.
how do sauna and ice baths compare in research after strength training?
In a 12-week trial, cold water immersion after resistance training was linked with quadriceps growth of around 2%, against 15% for active recovery. Leg press gains were 42% against 59% (Roberts et al., 2015). No study has found the same effect for sauna heat. Athletes still use cold water immersion when they need to feel fresh for competition the next day.
what session lengths did the recovery studies use?
The studies showing endurance gains used roughly 30 minutes at 87 to 90°C, often split across two sittings. Participants were healthy, trained adults.
when did the recovery studies schedule the sauna?
Within about 15 minutes of finishing training, in the trials that found plasma volume expansion and endurance gains. These studies found no documented benefit from heat before ordinary training. Heat acclimation before racing in hot conditions follows separate protocols.
do you need a sauna hat for recovery sessions?
No. A densely felted merino hat insulates the head from the hottest air in the room, and many people find longer sessions more comfortable with it.
General information only, not medical advice. If you're pregnant or have a health condition, talk to your doctor before using a sauna.
