Sunday, 2 May 2010

The three evils of Ironman

This week I gave a talk at my hospital about some aspects of Medicine and Ironman. Whilst doing this I camE up with what I have decided to call the 3 evils of ironman. Sure they are nothing new but I thought they might perhaps shed a bit of light on the issues facing some of us as we race. So what are these three evils?

Hypoglyceamia, Hyperthermia and Dehydration. Or in other words bad nutrition strategy, overheating and not replacing your fluids enough. What is interesting is how these are all linked and related to one other thing, your race strategy.

Hypoglycaemia (aka Bonking, the wall etc) occurs when you have used up most of your energy stores. Plenty has been written on nutrition and IM racing. The key factor being that without eating you cannot sustain a high enough power output to RACE your race. You may have all the fitness you like but if you race too hard to soon and dont feed you will become energy depleted. Your race then starts to fall apart because, as your blood sugar starts to drop, you become less efficient meaning that to sustain the same energy output your heart rate will rise more than it would with an effective nutrition strategy In addition your "central governor", the little voice in your left ear, will start telling your body to slow down for fear of your exercise causing your body long term damage. So the key is to find the optimum race speed/power output/HR that you can sustain and effectively digest your food. This takes practice but surprisingly few of my fellow IMers do religious nutrition training in the same way as we simulate the swimming, biking and running. Having done a few IMs most of us kind of think we know what it takes, but in practice a lot of people eat less in the race than they need or equally find they have to "review" there eating strategy on the side of the road.

The next factor to consider is how hot you get when racing. At above 25C most of us Brits who have not yet acclimatised will find the heat they generate challenging. If you do not dissipate the heat one of the first things that will happen is that you will lose your appetite.. a fatal mistake if this happens in the first few hours of your bike leg as you will not eat nor probably drink as much as you should. Since you have done all this training it will probably not be until the last third of the ride that this starts to become a factor, if you were not gonna run after it then this would not be an issue... how many of us get to the end of a long bike and then need a few long cold drinks to refresh.. perhaps we should practice getting home at the same weight we left (a good measure of successful hydration).

Clearly the more dehydrated we get the less efficient we get at losing heat since this is largely dependent on sweating. In addition dehydration pushes you heart rate up making us less efficient (so using more energy) and making us hotter still! This might explain in part the huge dropout rate from IM China of around 30%. Admittedly it was really hot (?38C+) and windy, but these extremes of temperature need specific adjustments in your race plan. Being less dense e.g having a low BMI and by just being smaller you have a huge advantage in the heat, and to some degree with hydration too since you need too drink less volume.

So I am now going to try doing a few rides where the objective is too come off the bike after 5 hours weighing within 0.5 kg of the weight when I left the house, and not feeling I so hungry I could eat a 17 egg omelette, chips beans and all the rest!

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