06 Jan, 2014

Turn up the Heat

Turn up the Heat

Chances are that most of your training has been done in cool moderate temperatures, either at the crack of dawn while the rest of the country is only thinking about getting up, or after work. I recall reaching 60km in the 2008 Comrades ‘Up Run’ in what were uncomfortably warm conditions. Road temperatures out on the route reached around 40 degrees, with air temperatures at 32 to 35 degrees. Runners were throwing up and the assumption was that they were dehydrated, which in all likelihood was not the case, but more on that shortly.


The last time it rained seriously during Comrades was in 1965. In 2011 it was cloudy and relatively cool, and in 2012 it started off cloudy with some strong winds coming into Camperdown. Clearly, hot weather is not always a given, but the chances of hot humid conditions are far more likely than not. For the purpose of this article, let us assume that it's going to be a hot and humid day – and anything other than that will be a bonus.



There are two high-risk conditions brought on by running in the heat that we need to be careful of:

1. HYPERTHERMIA: The body produces more heat than it can dissipate. Hyperthermia reduces muscle endurance and decreases performance levels. This is due to the dilation of blood vessels in the skin and pooling of blood in the limbs. As a result, the volume of blood returning to the heart decreases, and with it the amount of oxygen delivered to the muscles via the blood, which results in fatigue.

2. DEHYDRATION: This is a complex subject and covers far more than can be said in this article. In Comrades, often the bigger problem is not dehydration but over-hydration, which leads to hyponatraemia, an imbalance in the electrolytes in the body. Basically, what happens is that the salt content of your blood is diluted with the excess intake of liquid as a result of the over-hydration. Taking on energy drinks with electrolytes will simply make matters worse, as the intake of more liquid further dilutes the salt content of the blood. And the problem with taking on a mouthful of salt is that we become thirstier!



When running in any conditions, the key is to remain adequately hydrated but not over-hydrated. One way to determine how much liquid we need is to do a sweat test. Find a hot day with conditions as close to race day. Weigh yourself in the nude and head out for a 30min run at Comrades race pace. Don’t drink anything while running. When back at home, weigh yourself once more and multiply the weight-loss by two. For every kilogram lost in body weight, you need one litre of liquid per hour. So, if you weighed 70kg before the run and afterwards you weighed 69.5kg, as a general rule of thumb you would need to take on one litre (0.5kg x 2 = 1) of water every hour in similar conditions.



With Comrades only a few weeks away, start switching your runs now to the warmest part of the day. In general, most people acclimatise to temperature change within four to seven days, and if you run in the heat of the day for two weeks before Comrades, your body will be far more adapted to the heat come race day. Acclimatisation allows the body time to adapt and to learn to function optimally at the new conditions, and with adequate acclimatisation the decrease in performance is minimised.


Good luck with the last weeks of your training!