Tips for Running Safely in the Heat
- High Peak Running
- May 12
- 4 min read
Updated: Oct 22
1. Understand What Heat Exposure Does
Before diving into tactics, it helps to know why heat training works — and when it can backfire.
Physiological Adaptations
Plasma volume expansion: Repeated heat exposure forces your body to retain more fluid, increasing plasma volume. This aids blood circulation, reduces cardiovascular strain, and improves cooling capability.
Earlier, increased sweat response: You begin sweating sooner and at higher rates, improving evaporative cooling.
Thermoregulatory efficiency: Better skin blood flow, lower resting core temperature, and improved control over internal heating.
Potential hematological effects: Some studies report modest hemoglobin or red-cell mass increases, though this is less consistent than the plasma expansion effect.
Cross-condition performance gains: Interestingly, heat-adapted athletes sometimes see performance benefits even in cooler conditions — possibly via improved cardiovascular reserve or metabolic flexibility.
However — and this is critical — all heat adaptation protocols impose extra stress. You must manage the load to avoid overreaching. As Jason Koop notes, “Any heat acclimation protocol will induce a training stress.” (Carmichael Training Systems)
Additionally, adaptation decays quickly: after 48 hours without heat exposure, you lose roughly 2.5 % per day in heart rate control, 6 % in core temperature control, and up to 30 % in sweat-rate improvements. (Carmichael Training Systems)
Takeaway: Heat training is a potent stimulus — but one you must balance with recovery, tapering, and contextual demands (travel, race schedule, injury risk).
2. Heat Acclimation: Protocols & Best Practices
Your tip “slowly adapt” is spot on. Let’s now structure that idea into actionable plans, with caveats.
Duration & Timing
Generally, 7–10 consecutive days of heat exposure (with exercise) is a minimal effective block. (Carmichael Training Systems)
To maintain adaptation, you can “top up” with ~one heat exposure every 2–3 days.
If your taper or travel window forces a heat hiatus, you can reacclimate in around 4 days (though not fully).
Avoid doing heat work immediately before very hard sessions or races — the extra stress may blunt performance.
Methods for Heat Exposure
You don’t always need an ambient hot environment.
Outdoor running in heat – The most direct method. On very hot days, run in the environment you’ll race in (if feasible), but scale the volume.
Layering / clothing overload – Run in extra layers to artificially raise heat stress. Works best during easy runs or warm-ups.
Passive heat: sauna / hot baths / heated chambers – Post-run sauna or hot baths (20–30 minutes) can deliver heat stimulus without extra mechanical load. (Run Spirited; Trail Runner Magazine)
Combined strategies – Some endurance coaches use “double stimulus” (moderate run in heat + post-run sauna). Monitor closely for over-stress.
Safety & Monitoring
Track heart rate, perceived exertion, and core temperature (if possible).
Stop if you experience dizziness, nausea, or confusion.
Support adaptation with strong hydration, recovery, and sleep.
3. Hydration, Electrolytes & Fluids
The “drink to thirst” principle still works, but in extreme heat, thirst may lag actual need.
Pre-hydrate before runs.
Replace electrolytes, especially sodium, during and after.
Measure your sweat rate and individualize fluid/sodium intake.
Use ice slurries or cold fluids pre-run to lower core temp.
Palm or limb cooling can aid thermal regulation. (Wikipedia – Palm Cooling)
4. Fuelling & Nutrition
Heat increases reliance on carbohydrates — top off glycogen before sessions.
Smaller, more frequent fuelling helps digestion.
Combine carbs + fluids + sodium for simplicity and stability.
Eat high-water, high-electrolyte meals during multi-day heat exposure.
5. Clothing, Gear & Strategy
Choose light-coloured, reflective, moisture-wicking fabrics.
Avoid cotton.
Use ventilated caps and soak gear to enhance evaporative cooling.
Pace by effort, not by GPS splits — thermal strain accumulates quickly.
Break long efforts into short mental checkpoints to manage discomfort.
6. Cooling & Recovery
Douse head, neck, and arms mid-run.
Use cold showers, immersion, or contrast therapy post-run.
Schedule saunas or heat exposures only on lighter training days.
7. Acclimation & Stress Management
Share your route and expected return time.
Train with others in extreme heat.
Log temperature, humidity, and perceived effort after each heat session.
Integrate mental strategies like positive self-talk and visualization of cooling. (arXiv Research, 2023)
8. Sample 10-Day Heat Adaptation Block
9. Cautions
Skip heat sessions when ill or overtired.
Reduce load if resting HR or fatigue rise.
High humidity = less evaporation; lower effort accordingly.
Always prioritise safety and recovery.
10. Voices from the Ultra World
Trail Runner Magazine highlights that top ultra coaches view heat training not just as race prep but as a year-round performance enhancer.
The Ultrarunners’ Heat Acclimation Cheat Sheet by Jason Koop is a gold standard resource for structured, evidence-based heat adaptation. (Carmichael Training Systems)
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