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Heat Suit Training

By Runsense · Reviewed by Raphael Crawford-Marks, Founder · Last reviewed October 20, 2026

Heat suit training means exercising in a sauna suit or extra layers to raise your core temperature on purpose. Runsense does not put it in plans and treats it as something for very advanced athletes only. The studies show more hemoglobin in elite athletes, and none shows faster running because of it. A hot race is better prepared for with the lower-risk options below. It can carry real danger, so the risk section matters as much as the findings. This is general training guidance.

What the suit studies found

The research is in elite cyclists and skiers doing a large dose. In a 2022 study of elite cyclists, 50-minute sessions five times a week for 5 weeks in a heat suit raised hemoglobin mass by 2.6% and power at 4 mmol per liter blood lactate by 3.6%, against a 0.7% fall in hemoglobin mass and a 0.6% fall in power in a control group. The cyclists were tested in temperate conditions1.

In a 2022 study of 25 male elite cross-country skiers, the same 5 weeks of heat suit sessions gave 30 g more hemoglobin mass than a control group, with no difference in work economy, running speed at 4 mmol per liter, VO2max or a 15-minute running distance trial2. In 46 well-trained skiers and biathletes at a 3-week camp at 1,865 m, adding three heat suit cycling sessions a week raised hemoglobin mass 2.9%, against 1.2% at altitude alone, and again with no group differences in submaximal or maximal performance measures3.

Read these as more oxygen-carrying hemoglobin in elite athletes, which is not the same as a faster race. None of these studies tested a hot race or a recreational runner.

What a hot race needs

Getting ready for heat is done by repeated heat exposure, not by a suit. Across 211 papers, an average of 8 sessions of about 90 minutes at about 39°C lowered heart rate at the end of exercise by 17 beats a minute and core temperature by 0.43°C, and improved time trial performance by 3.1%4. Coaches of runners who race in heat find that most of the benefit comes in the first nine to eleven exposures and that it fades quickly, so the exposures belong in the weeks before the race.

For the lower-risk way to get heat exposure, see passive heat training. Start the race well hydrated, and see hydration and electrolytes for how much to drink.

If you use one anyway

The suit is for very advanced athletes who monitor themselves closely, and Runsense plans contain no heat suit session. Runsense does not coach it, so these are cautions and not a protocol:

The risk

Exertional heat stroke is a true medical emergency with potential for organ injury and death. A 2021 expert consensus statement says stopping activity and cooling the whole body quickly are essential for survival, and most exertional heat illness can be prevented by recognizing and changing the known risk factors5. It happens in ordinary road races: a 2021 study of the 2015 to 2019 Boston Marathons found 3.7 cases per 10,000 starters, and the races where they happened had average wet bulb globe temperatures of only 17 to 20°C6. A suit adds heat to that, and it traps sweat against the skin, so less of it evaporates and evaporation is how sweating cools you.

Safety

Stop immediately and cool down if you feel confused, dizzy, lightheaded or nauseated, or if your heart rate spikes. These can be signs of heat illness. Suspected heat stroke is a medical emergency, so call emergency services and start cooling right away. Do not rely on the old "stops sweating" cue, since an overheating athlete can still be sweating.

Do not use a sauna suit or extra layers if you are a beginner, pregnant, ill, dehydrated or have a heart condition, and check with a doctor if you are unsure whether it is right for you. Do not combine it with hard running or with alcohol.

Sources

  1. Rønnestad BR, Urianstad T, Hamarsland H, Hansen J, Nygaard H, Ellefsen S, et al. Heat training efficiently increases and maintains hemoglobin mass and temperate endurance performance in elite cyclists. Medicine and Science in Sports and Exercise 54(9):1515-1526 (2022). (Elite cyclists, 5 weeks of heat chamber or heat suit training versus control) ↩
  2. Rønnestad BR, Lid OM, Hansen J, Hamarsland H, Mølmen KS, Nygaard H, et al. Heat suit training increases hemoglobin mass in elite cross-country skiers. Scandinavian Journal of Medicine and Science in Sports 32(7):1089-1098 (2022). (25 male elite cross-country skiers (13 heat suit, 12 control), 5 weeks) ↩
  3. Rønnestad BR, Urianstad Odden T, Blindheim PM, Hansen J, Hamarsland H, Ellefsen S, et al. Heat training augments hemoglobin mass during a moderate-altitude training camp in well-trained endurance athletes. Journal of Applied Physiology 140(5):1298-1310 (2026). (46 well-trained cross-country skiers and biathletes (20 women, 26 men), 3 weeks, three groups) ↩
  4. McDonald P, Brown HA, Topham TH, Kelly MK, Jardine WT, Carr A, et al. Influence of exercise heat acclimation protocol characteristics on adaptation kinetics: a quantitative review with Bayesian meta-regressions. Comprehensive Physiology 15(3):e70017 (2025). (Bayesian meta-analyses of data from 211 papers on exercise heat acclimation) ↩
  5. Roberts WO, Armstrong LE, Sawka MN, Yeargin SW, Heled Y, O'Connor FG. ACSM expert consensus statement on exertional heat illness: recognition, management, and return to activity. Current Sports Medicine Reports 20(9):470-484 (2021). (Expert consensus statement) ↩
  6. Breslow RG, Collins JE, Troyanos C, Cohen MC, D'Hemecourt P, Dyer KS, et al. Exertional heat stroke at the Boston Marathon: demographics and the environment. Medicine and Science in Sports and Exercise 53(9):1818-1825 (2021). (136,161 starters at the 2015 to 2019 Boston Marathons, exertional heat stroke cases among them) ↩

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