I visited the Altitude Center in London, a popular acclimation centre for Marathon des Sables participants. Yes, jumping in a heat chamber to run does cost some cash, and not everyone can afford the luxury of doing that ahead of running MDS but, I reluctantly decided to fork out, given the heat is my biggest unknown and concern when it comes to being able to complete the race.

Whilst it was way too early to reap any benefit of heat acclimation for the race, I wanted to get a cheeky session in for two reasons; firstly, to really understand my sweat rate and how much sodium I can expect to lose (and start to get used to loading up on salt tabs) but secondly, I kinda wanted to scare myself a bit; which, safe to say, was a resounding success.

Since running my 100K back in September, I’ve been pretty consistent in my running, but have taken it down a notch overall and, with that, put on 6kg. My thinking was to get in a heat chamber and have a reality check, creating a catalyst for kicking off my final training block ahead of the race, with a focus on dropping weight too.

When I arrived at the Altitude Center, the place was as professional and impressive as I’d hoped, and that was matched by the knowledge of the staff who instantly put me at ease. As a partner of Precision Hydration, we did the sweat test first: a simple and non-invasive test where sweat is induced on the forearm by electrodes. It takes a bit of time for the sweat to ‘fill up’ the strange, swirly, catchy device; but it created a good opportunity to natter to staff about MDS and the vast number of people they help each year to acclimatise.

Going into the sweat test, I was pretty sure I was both a heavy sweater and losing a lot of salt, given after hard effort runs (and especially in summer) my clothes have the tell-tale white rings of salt left on them. However, to my surprise, once we tested the sodium concentration of my sweat, it turned out I am a low sodium sweater; which, to be honest, I was pretty happy about, given the task in front of me (107 days from now, to be precise… not that I’m counting).

So with my sodium loss rate in hand, all we needed now was to understand my sweat loss rate, to see how much sodium I was losing per hour… and so into the heat chamber I went (albeit via weighing myself first, of course, for the before/after figures).

We started off at 38 degrees in the heat chamber, at an easy 6:40/km pace. Not so easy in that heat though, to be honest. That said, I was happy enough running that for the first 20 minutes. The heat felt close, and it surprised me how well the chamber replicated the convection feeling of heat on your back from the sun. It was something else. Nick, the person looking after me for the session, would appear every 10 minutes to take my core temp from my ear, and after 20 mins decided I should up the pace to get my temperature up quicker…. I secretly took that as a good sign in my book.

So, at 20 minutes in, and with the chamber now about the 41 degrees Celsius mark, Nick got me running at 6:00/km pace. Anywhere else and that’d fall into an easy endurance run but in this chamber, that instantly felt like a different level. I immediately felt my metabolic temperature rising, and the 10 minutes until Nick returned felt like an eternity. I’d be lying if I said I didn’t start to worry/panic a little during those 10 long minutes. What have I signed up for? Who am I to think I can run the fucking MDS… ? I’d try to keep in mind: this is my first time in this sort of heat; I would acclimatise quickly when in Morocco; I can walk as much as I want; I am not at my fittest… but still, the minutes, nay seconds, dragged on. Imagine doing this for hours on end in direct sunlight in the desert, after fuck all sleep and multiple marathons in the days before… Anyyyyywwaayyyy.

Nick reappeared, was happy my core temp had also reached 40 degrees, and knocked the pace down to a walk on an incline. A welcome relief but only enough to maintain my now high temperature and impressive amount of sweating; not alleviate it at all. But that’s how heat chamber sessions work.

Once I was wrapped, weighed, and showered, we quickly worked out I am a heavy sweater and what I lack in sodium concentration I easily make up for in excessive sweating. So that firmly puts me back around the average mark in terms of sodium loss, and when it comes to MDS, that’s better than a kick in the teeth.

Did the session give me a kick up the ass? A little, yup. I’m determined to drop weight and ensure I hit the start line at MDS in the best shape I’ve ever been in. It shouldn’t be that hard but it is necessary.

As for the heat chamber; I will see you again, my dear friend, in the week before MDS, in my full kit, dressed like an absolute wanker. I look forward to it.