Why Heat Training is the Game-Changer for MdS

The Marathon des Sables (MdS) is widely known as the toughest footrace on earth not just because of the distance, but because of the environment. Over seven days, participants run the equivalent of six marathons across the Sahara Desert, often carrying their own supplies and battling daytime temperatures above 40–50°C.

For most runners, the heat is the hardest element. Even experienced marathoners who can comfortably handle 26.2 miles in cool conditions find themselves struggling when core body temperature spikes, hydration levels plummet, and every step feels twice as hard.

That’s why heat training is one of the most important parts of MdS preparation. Done correctly, it doesn’t just help you survive the Sahara, it allows you to stay sharp, manage your effort, and even enjoy the challenge.

In this guide, I’ll share how heat acclimatisation works, practical strategies you can use no matter where you live, and a sample plan you can slot into your MdS build-up.

The Science of Heat Adaptation

When exposed to heat stress repeatedly, the body undergoes a series of adaptations that make exercising in extreme environments safer and more efficient. These include:

• Increased plasma volume – more blood available for circulation and cooling.

• Earlier onset of sweating – your body starts cooling itself sooner.

• Improved sweat rate and distribution – sweat spreads more evenly, maximising evaporation.

• Reduced heart rate at a given workload – less cardiovascular strain.

• Lower core temperature during exercise – you feel more comfortable for longer.

• Perceived effort decreases – running in the heat feels easier.

How long does it take?

• Partial adaptation: 7–10 days of consistent exposure.

• Full adaptation: 2–3 weeks.

This means you don’t need to spend months in the desert before the race. With smart training methods, you can achieve significant adaptation in the weeks leading up to your MdS taper.

Practical Heat Training Strategies

Not everyone has access to a desert but that doesn’t mean you can’t prepare effectively. Here are the most proven methods:

1. Sauna Sessions

One of the most effective tools.

• Sit in a sauna immediately after training for 20–30 minutes.

• Training first raises core temperature; the sauna prolongs it, accelerating adaptation.

• Start 2–3 times per week, building up to daily use in the final fortnight before travel.

• Stay hydrated and listen to your body.

2. Overdressing Runs

If you don’t have a sauna, simulate heat by adding layers.

• Run in hoodies, tights, or jackets.

• Works best in cool climates where you can’t naturally generate heat stress.

• Beware of dehydration; weigh yourself pre/post to track fluid loss.

3. Heated Room Treadmill Runs

Create your own desert simulation.

• Close windows, use heaters, and run in layers.

• Easier to control environment compared to outdoor overdressing.

• Good for structured tempo or interval sessions.

4. Heat Chambers

Sports science labs sometimes offer access.

• Sessions in 35–40°C with controlled humidity.

• Provides a safe, measurable environment for heat stress.

• Great if you live near a university or elite performance centre.

5. Sauna Suits (with caution)

A last resort.

• Can replicate sweating stress but comes with higher dehydration risks.

• Use sparingly and only if supervised or experienced.

Hydration and Electrolyte Strategies

Heat training is only half the battle. Hydration is where many MdS runners fail.

Know Your Sweat Rate

• Weigh yourself before and after a 1-hour hot run (with no fluids).

• The difference = your sweat loss.

• Aim to replace ~80% of that per hour in desert conditions.

Electrolytes Matter

• Sodium is the key electrolyte lost in sweat.

• Aim for 600–1000mg sodium per litre of fluid.

• Test different drinks and powders during training so race week feels routine.

Practice Race Hydration

During training runs in the heat, practice drinking:

• 250–300ml every 15–20 minutes.

• Small, frequent sips are better than large gulps.

Mental Adaptation: Training the Mind for the Sahara

Heat training isn’t just physical. The desert pushes athletes into unfamiliar levels of discomfort. Building mental resilience is vital.

• Stay in discomfort longer: Extend sauna sessions slightly beyond comfort levels.

• Use visualisation: During long runs, imagine the desert environment — heat shimmering off the horizon, sand underfoot.

• Chunk the challenge: Mentally break MdS stages into small goals (next checkpoint, next dune).

• Mantra use: Repeat phrases that reinforce calm and strength, e.g., “I’m strong, I’m ready.”

Sample 2-Week Heat Training Protocol

Here’s a structure you can add to your race build-up (ideally 3–4 weeks before tapering):

Week 1

• 3x post-run sauna sessions (20 mins).

• 1 long overdressed run (90 mins).

• 1 treadmill session in heated room (60 mins).

Week 2

• 5x post-run sauna sessions (25–30 mins).

• 2 long overdressed runs (90–120 mins).

• 1 treadmill heat session (75–90 mins).

Important: Reduce heat stress in the final 3–4 days before flying to Morocco to arrive fresh, not fatigued.

Mistakes to Avoid

• Starting too early – Adaptation fades if you peak months before the race.

• Neglecting hydration – Acclimatisation without fluid management won’t prepare you.

• Overdoing overdressed runs – Risk of heatstroke. Use sparingly.

• Skipping mental prep – Heat stress is as much psychological as physiological.

Train Smart, Race Strong

The Marathon des Sables is as much about mastering the Sahara as it is about running. With structured heat training, smart hydration, and a resilient mindset, you’ll not only survive the desert, you’ll put yourself in the best position to enjoy the experience and reach the finish line with confidence.

👉 If you’re preparing for the Marathon des Sables and want a personalised heat acclimatisation plan, I offer dedicated Marathon des Sables Coaching — built on my own desert running and coaching experience. Together, we’ll make sure the Sahara feels like home.