The Marathon Des Sables (MdS) is a 250km multi-stage race across the Saharan Desert in searing temperatures, often quoted as the “toughest footrace on the planet”. This year the University of Brighton’s Environmental Extremes Lab (EEL) supported 5 athletes with their preparation for the event which was to be the hottest and reportedly in the Guardian, the most challenging to date. This was also a baptism of fire for our new cohort of MSc Applied Sport Physiology and MSc Applied Exercise Physiology students to develop their practitioner skills, who had only started their degree a few days before. Read on to find out the triumphs and near tragedy from our 5 MDS athletes and some reflections from the EEL Team.  

Using protocols from our previous heat reaction/mitigation research developed here at the University of Brighton in our Welkin Laboratories, each of the MDS athletes completed a pre and post heat tolerance test developed by now Dr Jess Mee, interspersed with four heat acclimation (HA) sessions, based on MDS research from another of our former PhD students, Dr Ash Wilmott. All six sessions were completed in our environmental chamber set at a temperature of 40˚C with a relative humidity of 40% as close to the date of departure as possible. The four HA sessions involved a combination of running/cycling-based exercise, aiming to maintain an internal core temperature of 38.5˚C. Once they achieved this temperature (~30 min), the athletes continued to exercise or rested passively to stay above this core temperature threshold for a further 60-minute if possible! Due to the intense nature of the exercise and the heat stress to mimic the anticipated conditions in the race, athletes were able to take on fluids if required during the HA sessions. Post sessions, involved athletes naturally cooling to safe levels so as not to reduce the heat adaptation effect from aggressive cooling. Nevertheless, a variety of cooling measures were on hand in the early sessions when needed and athletes did not leave until the EEL team judged they had recovered sufficiently.

After completing the six sessions, adaptations that were consistently observed amongst the athletes, included a reduction in their core temperature and heart rate (as evidenced in the figure below where the pre heat tolerance test red dot, moved to the post heat acclimation blue dot).

Perceptual scores and heat illness symptoms also lessened; clearly demonstrating the collective benefits of HA. The heightened perceptual awareness and greater sensing of heat illness symptoms were invaluable alongside the thermoregulatory and physiological adaptations as testified by one of our MDS athletes:

“For me personally, the newly acquired knowledge of how much I sweat but more importantly what it feels like as my core temperature rises, to know what it feels like when it gets too high and what to do if that happens, was the difference between my completing the event and not”

The MDS Race Itself

This year was like no other, with the excessively high temperatures (~50˚C most days) and the Norovirus rampaging through the athletes and staff tents. Typically, drop-out rates from the race are 5-10% of the starters – this year it was 50%! 700+ started…~350 finished. As one of our athletes recounted…

“The excessive heat and a camp bug decimated the pack. It was akin to a zombie movie most days and the soundtrack to every evening was dry retching, people puking and a few unfortunate ones s****ing themselves!”

“The long day – 50 miles of joy saw 200+ people drop out on the day. Ridiculous terrain and a real mental battle. Was forced to stop and sleep by Karen and Tom and honestly that saved my race (zero sleep the night before because of the bug, could only consume/keep in 400 calories all day due to the bug, and that had to fuel me through 50 miles!)

This athlete recounted he had never had a blister in his life, but got eight on the long day. The heat and sickness meant you walked more, which meant you’re on your feet for longer, which means your gait changes and for one of our athletes, resulted in two golf ball sized blisters on the ball of each foot…

“Finishing – the medal, the joy. Probably forever one of my greatest accomplishments. Charity – £6,000+ raised for an incredible cause. The only word I have found to describe the experience is ‘brutal'”.

In our preparation of the MDS athletes, we talked a lot about their hydration and food strategies, as well as recognising their own hydration status. The phrase, “your nose knows” was recounted more than a few times to encourage athletes to become accustomed to how their wee smelt! It was encouraging to hear back from one athlete who stated:

“I sipped water every 15 mins, took 2 salt tablets every 30 mins without fail and glugged half a litre at every checkpoint. I was militant about this given the heat. I was not going to fail at this event on something within my control”

Another athlete described their account of the event as a very testing experience indeed. After completing stage one with minimal issues, they ended the evening in their tent feeling very unwell with bacterial gastroenteritis! After a poor night’s sleep, stage two was spent with continual vomiting and diarrhoea on the hottest stage of the event (an unbelievable 56˚C!). Having to stop every 10km was less than ideal and they mentioned the need to reduce their pace significantly, just to stay in the event. The athlete recalled that many individuals had not prepared for the expected temperatures let alone the actual temperatures and behaviourally, athletes were resting in direct sunlight and minimising the amount of water taken on due to thinking less fluid would save weight and reduce energetic cost. Of course the opposite was happening…increasing the chances of heat-related illness. By the end of stage three, half of the athletes sharing a tent with this individual had withdrawn from the race, one had 7 drips of IV fluid, while one was urinating blood. Despite this, the athletes attempted to stay in good spirits and keep heightened morale levels in amongst the most challenging conditions.

Retrospective feedback from the athletes clearly emphasises the grueling challenge facing the competitors in these extreme temperatures, highlighted by the photo below which was taken moments before the thermometer broke in 50˚C!

With these very open and honest reflections in mind, along with the many challenges faced, we are very pleased to report that four out of the five individuals still were able to complete the MDS, placing in the top 55% of the 353 runners who completed the event.

Unfortunately, there was also one withdrawal from the five athletes due to a cardiac arrest on day 2. The athlete’s heart stopped for 1 min 57 s, but was very fortunate in the circumstances to have collapsed at the feet of one of the medics who had a defibrillator to hand! The athlete, who did know there was a greater risk with an existing heart condition, stated that they had felt okay up until that point, but unfortunately the extreme heat (56˚C) and excessive long duration of exercise contributed towards the cardiac arrest. The athlete was thankfully able to recount his experiences later to us, noting the consequences could have been much worse, especially without the heat acclimation prior to leaving.

“I honestly feel that the environmental chamber prepared me well for what the conditions should have been, but the freak conditions really were my undoing.”

We are pleased to hear the athlete is back in the UK recovering and is also out running again, albeit  at low mileages and low temperatures! This extreme case should be a reminder to us all of the perils of extreme ultra-endurance events like this, but also the importance of heat awareness in the form of screening, heat acclimation and education.

Alongside the physiological and behavioural knowledge acquired by the athletes, our new 2021/22 MSc student cohort also experienced an extensive introduction to environmental physiology, getting enthusiastically stuck into the MDS project just a few days into starting their new degree! Led by Dr Neil Maxwell, and with the support from our team leaders (Bill Norton, Rebecca Relf, Greg Wright, Chanel Coppard and Harriet Dodd), they were able to gain a great understanding of environmental extremes in practice, develop their harder technical skills alongside their softer, interpersonal skills.

To summarise, it is desperately sad to hear of the passing of a French competitor  in this year’s MDS and our thoughts go out to the family and friends of this athlete. For us here in the Environmental Extremes Lab, this news only reinforces our collective vision:

Through our research and education, people will decide how to prepare for safe and effective exercise in environmental extremes to optimise performance and reduce risk of illness.

The key take-home message from this blog post and the individual accounts from the athletes we supported on their MDS journey, is that heat acclimation alongside heat tolerance testing is essential prior to competing in extreme heat. It provides many benefits – identification of your individual reactions to exercising in the heat and a level of risk stratification, both central (e.g. reduction in physiological strain) and peripheral e.g., improved sweating response) thermal adaptations, educational awareness (not least of pacing strategies), recognition of heat illness symptoms and advice on how to cool the body. An important benefit, is that it can give athletes confidence but also a healthy respect for the heat stress prior to departure. All athletes supported through EEL mentioned that the number of competitors who engaged in heat acclimation training prior to flying out was minimal. However, the feedback and information provided from those who recently returned from the MDS clearly highlights and emphasises the importance of heat acclimation support. We encourage all competitors, especially those residing from temperate climates, to seek out such support ahead of their own extreme challenges.

Not only did our team receive some very kind feedback from the athletes indeed and acknowledgement to the professionalism of our students, but also a heart-warming story, which I think is a great way to end this blog post, so we will leave you with this:

“Big thanks to the team Billy on showing me the cues for when I was heating up, the importance of consistently drinking water and the importance of taking a step back to reassess how I was feeling. Thanks to everyone again Billy, the heat acclimation was invaluable”

“I just wanted to say massive thank you for your help in preparing us for our desert adventure. The training itself and your advice that followed made all the difference between being able to cross the finish line (in good shape) and becoming the dark statistic that is the 50% of participants who dropped out. I followed your advice to slow it down from day one and to always have a wet buff over my head and face which served me well to remain strong throughout the race and not get sick in any way.”

“I must also congratulate you on your team, Harriet, Billy and the rest of the gang were extremely professional and a phenomenal wealth of information that I couldn’t have survived without. Harriet’s words of ‘drink’ still rattle around in my head today!”

“One of my happiest takeaways from the event was the long day at CP2 which was just after a fairly long dune section in the midday sun. I was very toastie so was taking a bit longer at the CP to cool down before moving on. A lad called Dan, who I’d run with a bit the day before and who was a top lad with a young family who was desperate to complete the event to inspire others, ‘landed’ on the rug next to me. He was really struggling, overheating etc. and started to panic. Having had one competitor sadly pass away a couple of days before, people were far more conscious and, in many cases, scared of what could happen to them. Dan called over one of the staff and said he wanted to quit. He hadn’t realised it was me standing next to him – I asked him why he wanted to stop. He said he was so hot and had pins and needles in his hands. I quickly explained to him what had happened to me in the environmental chamber back at Brighton and that what he should do before making that final decision was to take however long he needed to cool himself down (the cut offs were very generous, and he was hours ahead of it). I said the pins and needles would likely go and he’d be okay to go again but it was obviously up to him. Anyway, long story short he told the officials he would wait and see. He later told me he lay there for an hour or so, felt well enough to continue and moved on. He eventually completed the long stage and then the final marathon. I saw him at the end and a few times again before leaving and there wasn’t a happier person in the camp. He was so excited to get home and show everyone and has talks planned at primary schools to tell people about the event. He kept saying it was down to me that he didn’t quit – I passed the credit straight on to you guys there. I only had that knowledge because of my time with you and to have been able to play a small part in making someone else’s dream a reality is really special and something I wanted you guys to know, as I know you’ll be made up you indirectly helped someone else complete it.”

“I would also like to mention how proud you and the university should be of the individuals who supported us. They were an absolute credit to you. They couldn’t have been more welcoming, accommodating, friendly and supportive.  All bar none I’m sure will go on to be very successful.”


To all the leaders and students who made this year’s MDS support programme work and provided such a professional and well executed service, we thank you!

Thanks to our MDS Leaders: Chanel Coppard, Harriet Dodd, Bill Norton, Rebecca Relf and Greg Wright

Thanks to our MSc Applied Sport/Exercise Physiology Students: Kate Buntine, Karolayne Castro-Alencar, Kayane Castro-Alencar, Jack Donnelly, Thomas Holloway, Alex Jago, Nathan Little, Luke Row, Lorien Salmon, Niki Sapalidou, Saurav Vijendran, Evie Winterton

Thanks to visiting PhD student: Herve Di Domenico

Thanks to all the athletes: for sharing your stories and photos and being so brave and resilient throughout this incredible journey…we are truly in awe!