• Pierre Meslet is a French ultrarunner who completed the Marathon des Sables (MdS) in October 2021 for the first time and placed a remarkable 9th. The MdS is a 7-day, six stage, ultramarathon which takes place in the Sahara Desert and covers a total distance of ~235km. Pierre completed the five main stages in an impressive 25-and-a-half hours
• MdS requires athletes to carry all of their kit, fuel and other supplies. The only exception to this is water and salt capsules which the event provides on course
• The self-sufficient nature of the MdS ensures athletes have to plan ahead, so Pierre carefully dialled in his fuel and hydration needs with plenty of pre-planning and went out to Morocco as well-prepared as an athlete could be
• One of the greatest challenges of the MdS is the high temperatures the athletes face. This year was no exception and in fact the temperatures were particularly brutal, with some of the highest temperatures ever seen due to the time of year (the pandemic caused the race to be moved to October rather than the usual March for 2021). For the first four days of the week, temperatures were >50℃ at the height of each day
• On top of this, there was a severe bout of sickness that affected many of the runners. The temperatures and illness sweeping through the camp meant there was a higher than average dropout rate. Pierre wasn’t completely unaffected; at the beginning and end of Stage 3 he suffered some sickness, but by responding sensibly with his hydration and fueling, he managed to recover and keep going strong for the remainder of the week

Hydration

• As part of his preparations, Pierre was sweat tested by Precision Fuel & Hydration Sports Scientist, Abby, two weeks before the event. The test revealed that Pierre loses 921 milligrams of sodium per litre (mg/L) of sweat, making him a ‘moderate salty sweater’
• Independently, Pierre underwent some sweat rate testing to determine how many litres of sweat he loses per hour in conditions replicable to those of the MdS (Pierre was fortunate to do some hot weather training in the months before the event). This was found to be in the region of 1.5 litres per hour (L/h). As a result Pierre was able to calculate his hourly sodium loss to be approximately ~1500mg sodium per hour
• Understanding what he was losing allowed Pierre to plan an effective hydration strategy. In practice, this involved consuming 1 x PH 1500 effervescent tablet each hour in 500ml/16oz plain water which made up the backbone of his hydration strategy. He also periodically supplemented this with the salt capsules handed out by the organisers of the event to stay on top of his sodium losses. Other smaller contributors of sodium were his carb-rich drink mix and on a few occasions 50g of salted nuts
• When determining an athlete’s sodium intake, it’s important to consider the relative sodium concentration (sodium intake in relation to fluid intake) of their consumption. Overconsumption of fluids will dilute an athlete’s sodium intake. Pierre did a fantastic job of balancing his sodium intake with how much he was drinking; during the first four stages of the race he was ingesting a relative sodium concentration of between 1472 and 1572mg/L each day. Right in the ballpark he needed to be!
• When we caught up with Pierre post-event we asked him how helpful he felt having an Advanced Sweat Test was to his preparations and performance in the desert. Pierre said “I don’t think it was helpful, I think it was essential. I’ve been running for 25 years, and I don’t think there has been a single fueling or hydration product that I have discovered over the years that has worked so well. The Precision Fuel & Hydration Sweat Test and electrolytes changed the way I drink in races.”
• Like his refueling, Pierre did a fantastic job at making sure he rehydrated effectively between stages by drinking ~2-2.5L PH 1500 each evening. This in line with the recommendations for optimal rehydration
• He was also consistent with starting each morning with one PH 1500 tablet, drunk alongside his breakfast of porridge which ensured he was starting each run adequately well-hydrated (a concept we call preloading). This is important ahead of any endurance event but even more so for a multi-stage event when an athlete may be dehydrated from the previous day

Fueling

Conclusions

• Pierre’s result was beyond his expectations for the event and his satisfaction with the outcome was evident in his Spinal Tap-esque rating of 11 out of 10!
• Pierre’s performance is a testament to how well he prepared. This doesn’t come down to any one factor but a combination of nailing his training, kit preparation, heat acclimation, and his fueling and hydration strategy
• Pierre didn’t suffer from muscle cramping, endured minimal GI distress and no dips in energy levels throughout the seven-day event. His recovery following the event was also exceptional, he said “I’m telling you, I ran hard, I really pushed myself the whole week. I didn’t have any single cramp, any single muscle fatigue, and the day we came back to the hotel I was running with one of the photographers for an hour and a half on the trails near the hotel - which isn’t supposed to be possible!”
• Pierre was surprised to find himself with the race leaders in this event and plans to return to race MdS in 2023 to see how well he can do when he’s racing from the very beginning. We can’t wait to see how he does!