50°C Heat. Endless sand dunes. 270 Kilometres. 7 Days in the desert. Everything you need carried on your back.
That is Marathon des Sables Legendary — it gets hyped as one of the toughest foot races on Earth. It's not just a test of physical endurance, but also a challenge of resilience, and the ability to adapt to the unknown — the Sahara Desert.
Hi, I’m Chelsy, Brand Manager and Product Designer for AmSTRONG. I completed the Marathon des Sables Legendary 40th Edition in April this year. At AmSTRONG, I always design for people to get moving and make everyday adventures a little easier, and MDS gave me a chance to put that mission to a pretty extreme test.
In this blog post, I’m sharing the pillars of my MDS prep and what it took to survive a 7-day, self-sufficient race in the desert!
If you’re interested in becoming a Legend — the title given to MDS Legendary Finishers, I hope my experience helps you conquer the desert and start with a little more confidence than I had.
Despite how daunting it sounds, the MDS race isn't reserved only for the elites. With a solid fitness base, smart gear choices, and thoughtful preparation, crossing that finish line is far more achievable than most people think.
Looking back, my success in the desert was entirely built over the 10 months of preparation, just after I signed up for the race in June 2025.
My MDS Playbook:
- My starting point
- The 3 phases of my 10-month training
- What is "Gram-efficient" Game?
- Fuel right, pack smart — nutrition plan and gear prep
- Lessons from experience racers
- Don't miss out the mental prep
So where did I start?
By the time I decided to go for MDS, honestly — I knew nothing about trail running.
I was just a gym regular who also enjoyed tennis and wake-surfing. I worked out 3-4 days a week. I ran and hiked, but nothing too intense. Ultra-distance running? Multi-day races? Camping? ZERO EXPERIENCE!
Certainly, taking on a 270km challenge in the Sahara was a wild decision for me. Even my friends and family questioned about it. Somehow, I believed it wasn’t an undoable task. My goal for it was simple: finish the race, ideally with as little suffering as possible. Above all, I was curious — I wanted to put myself out there and see what 10 months of focused and committed preparation could bring me.
The 10-Month Training Blueprint
Going from zero trail experience to MDS Legendary, the preparation had been overwhelming at first. There were so many things to figure out — how much should I run, how often should I train, how far was far enough, and whether my body could actually handle it.
To help myself organise and track the progress, I started a spreadsheet to log every workout, and set clear monthly focus and goals. I wanted to ensure I was progressing in the right direction.
Now that I look back, those 10 months naturally fell into three phases.
Months 1–2: Find My Rhythm
At the beginning, my biggest goal wasn't to run far. It was simply to get used to training regularly and to build a solid aerobic base.
I focused on developing a routine that I could sustain week after week. I gradually increased my training volume and aimed to accumulate 100–150km each month.
At that time, there wasn't any impressive progress. It could feel particularly tiring and hard to recover from sometimes, but I knew every session was another brick in the foundation. I needed to make running regularly feel normal.
Months 3–7: Building The Engine
Once training became part of my routine, it was time to build the engine. This became the core period where I established my endurance.
I started incorporating two or three 30–50km trail runs every month alongside back-to-back training days that simulated the accumulated fatigue of a multi-stage race. I also dialled in some race-specific practices, e.g. weighted hikes, night hikes, and heat acclimation.
Those long distance training taught me things that a normal run simply couldn't.
How much water do I need? How often should I eat? What happened to my body after 6 or 8 hours? What should I do when my body starts telling me it has had enough?
The training was no longer just about becoming fitter. It became a series of small experiments. I'd try something, see how my body responded, make an adjustment, and test it again the next time.
Months 8–10: Consolidation & Fine-tuning
As the race got closer, to avoid injury, I didn’t push the intensity further. I maintained my training volume while using my long runs as opportunities to adjust the details. I tested my nutrition strategy, and tried out the gear, made sure every piece of them worked exactly as wanted.
By this point, I had a much better understanding of what my body was capable of, and that was a crucial piece of clarity that allowed me to reduce uncertainties and fine-tune the rest of my race prep before heading to the desert.
Nutrition & Gear Prep aka The "Gram-Efficient" Game
If training built the engine, nutrition is the fuel and gear is the support making sure the ride is smooth. Mastering both could unlock your best performance, but getting them wrong would possibly ruin your race.
One of the most iconic features of MDS is the self-sufficient format. Apart from water, everything you'll need for the race has to be carried on your own back — food, sleeping gear, cooking kit, and other personal essentials. No bag drop or outside support. That’s why keeping the bag light was my top priority. I set a target of 8kg for the total weight of my bag (without water). Throughout the prep, I was mad about getting the most value out of every gram I packed and finding ways to cut a few grams from every gear.
I call it the “gram-efficient” game!
The Fuel
I categorised nutrition into 3 areas: meals at bivouac, nutrition for racing and comfort snacks.
Meals at bivouac
2 meals per day and they were my breakfast and dinner. I had various flavours of dehydrated meals (Korean bibimbap was my favourite!) and drip bag coffee. They’re quick to prepare and easy to carry along. I also repacked the meals with vacuum packing bags and removed the unnecessary packaging from the coffee pack, so as to save space and shave a few grams off per pack. Yes, every gram matters!
Nutrition for racing
Throughout the preparation, I experimented with different brands, flavours and types of nutrition to find what worked best for my body. One thing I learnt fairly quickly was that our digestive system isn't particularly generous during long efforts. Instead of relying on gel forms of nutrition, I switched to solid food. That decision turned out to be the right one. well… mostly. I still had diarrhoea on the 4th day, which was the 100k Long Day. It was really rough and hectic. But at least I knew my nutrition strategy wasn’t making things worse.
I also optimised my “gram-efficient" game by getting only food or bars that offered at least 200 kcals for every 50 grams. Reading nutrition labels became strangely exciting and it was the first time of my life desperately searching for high-kcal food. Lol
Another thing I looked into was hydration. It is hot and extremely dry in the desert. Humidity during our race was only around 13%. Because sweat evaporates so quickly, it's easy to underestimate how much fluid and electrolytes you're losing. Electrolytes became non-negotiable. Not only for maintaining performance, but also for reducing the risk of dehydration and heat-related illness. For MDS, I brought various types of electrolytes - salt tablets, pills and drink mix.
Comfort snacks
I’m not sure if it’s just me, but I feel comfort food is a bit overrated. I did prepare some because many experienced runners told me so, but after all I would rather have traded the weight of those snacks for energy bars for extra kcals.
Choosing Gear, Wisely
Unlike calories, gear can't easily be adjusted or repaired once the race begins and you’re very unlikely to bring spare gear. Every item needs to be tested, trusted and proven long before race day. Never take anything that you haven't already tested. The desert is unpredictable enough. Your gear shouldn't be.
If you're new to long-distance racing or multi-day adventures—as I was—you'll probably spend months to research, buy, test, tweak, and re-test.
On-Body Gear: Comfort Takes the Crown
For clothing and anything I wore while racing, comfort beats the chase of absolute lightness. I opted for merino wool over polyester for my top and socks for breathability and natural odour resistance. In a race where showers and laundry don't exist, you simply appreciate those qualities.
The Backpack: Find The Perfect Fit
Finding the right backpack turned out to be far more difficult than I expected. At first, I simply bought one. It was incredibly lightweight, well-built, and looked perfect — until I loaded it. The flaws hit. It was just too light that it sacrificed the support on back and shoulders and the fit wasn’t right. I tried to search for alternatives. However, the packs with better support were mostly designed for hiking or camping. They carried weight well, but they were heavy and lacked the quick-access features for racing.
Nothing seemed to strike the balance I was looking for. Then I remembered… I'm a bag designer. So, in the very, very last minute, I made myself a 25L race backpack that combined the support I needed with lightweight construction and easy access to everything I used throughout the journey. Crossing the desert with a pack I built from scratch was one of the best decisions I made. And yes… I was quite proud of it.
Everything Else: The Minimalist Hacks
For everything else in the bag, I simply chose the lightest option that still did its job.
- Micro Everything: Travel-sized or kid-sized gear only — I used a kid toothbrush and carried toothpaste and face wash that were just enough for 7 days. Nothing extra.
- Multi-purpose Everything: I used my food bag and spare clothes as pillow. Safety pins were best for hanging washed clothes.
- Layer Everything: Because in the desert, temperature control is all about stacking systems, not single items. To beat the temperature swing, I got a 420g down-filled sleeping bag (10℃, women's size), and layered up with a down jacket and windbreaker to stay cozy.
The Last Puzzles of The Prep
Last but not least, there’re two things that helped me a lot in getting myself ready for the MDS adventure.
Reaching Out to The Experienced
Throughout those ten months, I got chances to meet many MDS alumni and experienced ultra-distance runners. Every conversation taught me something different. Some shared practical tips on gear and nutrition; others explained how they planned each stage or packed their backpacks; a few simply told stories about things that had gone wrong.
Months later, during the 100k Long Day, I found myself in a situation not only struggling with diarrhoea, also sort of heatstroke. I wasn't entirely sure what was happening – I just felt dizzy and lacked energy – but at that moment, I remembered a story about an MDS runner who was forced to withdraw due to severe heatstroke. That memory made me reconsider my instinct to push through. Instead of stubbornly continuing (which would have been my usual approach), I decided to stop at a checkpoint, rest, cool down, and wait for the sun to set before moving on.
Experience doesn't just give you answers. Sometimes, it helps you recognise a problem before it becomes a disaster. Many runners are incredibly generous with their advice, and their experience saves you months of trial and error—or even saves your race.
At The End, It's a Mental Game.
Mental prep for ultra-distance events is just as important as physical training. All runners have their own tactics to help them get through extreme fatigue.
People often ask what kept me going during that 270km or what pushed me through when my body just couldn’t. Some of them expected a life-changing thought or a deeply emotional plot twist. Unfortunately, my answer isn't as interesting or dramatic haha. I simply wanted to finish. I just kept my head down. And surprisingly, that was enough.
Let me explain — from prep to race, this might sound a little strange, I approached MDS almost like a work project.
I expected problems ahead, measured my capability, researched on methods, drew plans and executed tasks by tasks. Whenever I faced a challenge, I rarely asked myself, "Can I do this?” Instead, I asked, "How do I solve this?"
Little by little, the unknown became familiar. Every uncertainty became something I could prepare for. That process gave me confidence — not because I believed I mastered it or I expected everything would go perfectly, but because I trusted my prep, providing me a grounding to deal with what was likely to happen.
This mindset also helped me ease the lows at race.
Many runners talked about repeatedly reminding themselves of their WHY. But I realised I hardly did that at all. When things became difficult, instead of thinking about the drive behind, I tended to switch myself into problem-solving mode and went back to my MDS playbook I had built in last 10 months. To me, it was more manageable when the big challenge was broken down into smaller problems. I always tried to focus on what I could do and never let the pressure take over.
Ten months of preparation. Seven days in the Sahara. One finish line.
That's how my Marathon des Sables Legendary journey unfolded.
Looking back, MDS Legendary was never just about running 270km across the desert. It’s the preparation, the small decisions, the unexpected setbacks, and all the moments when you choose to keep going. And I think that applies to almost anything in life.
For me, the biggest takeaway from MDS was discovering how much can happen when you give yourself the time, preparation and patience to find out what you're capable of.
And perhaps that's the real adventure.
Do you have an adventure ahead? Are you planning for your MDS? Share with us!
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