Running from Shadows

My Marathon des Sables . . . and beyond

The Walking/Running Sodium Factory

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A recent heatwave affecting southern Europe had also spread to north Africa, giving a toasty 40-43C from around midday right through to early evening on a recent few days holiday to Marrakech (temperatures expected over July and August, not early May!). While there was nothing more strenuous than trips from a riad (fortunately with a dipping pool) to the souks and cafe bars and alleyways surrounding the main Jemaa el-Fnaa square, it was a reminder of how uncomfortable heat can become.

Which got me thinking about my heat acclimatisation plans for The Ancient Khmer Path race in Cambodia later this year and how different they will have to be from my plans used for my desert races the Marathon des Sables in 2012 and the Sahara Race (Jordan) in 2014.

The desert heat is dry: regardless of how hard the body is working, the dry air simply sucks away litres of sweat from the skin. As desert competitors know, it’s dangerous to rely on visible sweating as a reliable indicator of impending dehydration. Thirst is a more useful tell-tale sign, but there’s a very fine line between an “acceptable” level of thirst which is always there throughout the race (trying to maintain full hydration is difficult on water rations) and a critical level of thirst where, unexpectedly, the body starts to shut down.

As I’ve known to my cost.

The Cambodian jungle, fields and tracks will see an altogether different form of heat: wet. While there will be blazing sun and hot temperatures not considered unusual in southern Europe (reports of previous races have seen 30C at 7am) the unknown for me will be its combination with very high levels of humidity: 70%-95% is to be expected . . . all day, and all night.

Punishing stuff: in the 2013 edition of the Ancient Khmer Path a competitor was airlifted to a Thailand hospital in a critical condition after a number of IV drips (she recovered) and the next day’s race stage was very sensibly neutralised by Race Director Stefan Betzelt.

So with no dry air doing the job of pulling sweat from my skin as I run/walk/crawl my way across the remoter parts of Cambodia, I expect to very quickly from the start get completely soaked and stay that way throughout the race. Race wet, sleep wet. I’m sure I’ll be pretty pungent after a week of running and sleeping on the jungle floor in a hot tent.

Hence more so than in either of my MdS or Sahara Race, this combination of heat and humidity is the most worrisome aspect of the race.

So I’ll take a three-pronged approach:

(1) starting this month, lose a lot of weight: 2-2.5 stone (12-15kg) (!) should do it . . . the more fat that surrounds my exercising muscles in the expected heat, the harder it will be;

(2) acclimatise: it’s a little useless to start this more than 10-14 days before the race as the body quickly loses the benefits of acclimatisation, so this will come later;

(3) resolve my electrolyte intake levels: reduced levels of these lost through copious amounts of sweat results in dehydration, bloating, sickness, nausea, cramps . . . and a high chance of another Did Not Finish!

On this last point I took myself off to the Porsche Human Performance Laboratory at Silverstone last year to see if there was anything they could find that might solve the gastric problems I had at the Sahara Race (Jordan).

They gave me a hydration test to calculate my genetically-acquired sweat/sodium concentration. The result? “Very High” . . . on a scale that finished at, er, “Very High”.

What they found was that per litre of sweat that my body produces I excrete an impressively whopping 1514mg of sodium. To compare this level, the medium range of test results is 800mg to 1100mg per litre of sweat . . . and the measurement scale stops at 1650mg. Because this level of sodium is genetically-acquired it can only change a little from whatever I can do.

In effect, I am a walking/running sodium factory.

That test result may explain all those races of years’ past finished with salt-stained T-shirts as well as perhaps the IV drip experienced during my MdS. But it could also explain the problems I had which led to my DNF at the Sahara Race (Jordan): a bloated stomach, nausea and a burning oesophagus could have been caused by having too much sodium intake.

So for the MdS and my unconscious collapse and IV drip I may not have taken enough sodium. For the Jordan race I may have been taking too much.

So what’s the ideal sodium intake for me?

Armed with the above statistic, that’s the next test, when I get around to it. Generally speaking, a weigh-in before and after a 1 hour run during which nothing is consumed will indicate, broadly, my sweat loss: for every 1lb lost in weight that’s roughly equivalent to 500ml of sweat.

And 500ml of sweat will mean I will have lost around 757mg of sodium which will need to be replaced.

How I’m supposed to calculate all this in the Cambodian jungle is anyone’s guess, as I don’t intend to take my weighing scales with me.

But knowing these facts gives some useful guidelines: I need to take quite high levels of sodium with my other electrolytes in my water. But too much may mean I will bloat and feel sick and suffer oesophagus burns . . .  so ease off the sodium and try and drink more plain water. Feeling sick without bloating? Consume more sodium to bring back a balance.

I think . . . A summer of experimentation will follow. And some significant weight loss: six months isn’t that long.


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