The other aspect I hadn’t even considered when signing up to Alpe D’Huez was the effect altitude might have on my body. A bit of a worrying oversight really. Luckily my coach came up trumps again as she had links to the Loughborough University Sports Science Services Department which had an altitude testing facility. The idea is that you do a control test involving a 30 minute bike set followed by a 30 minute run to capture your body’s normal response to exercise. This is then repeated in an altitude chamber a week later to measure the difference in how your body reacts to the conditions.
The method for measuring the difference was twofold. Firstly, blood samples were taken at regular 5 minute intervals to measure blood oxygen saturation and the blood lactate response (blood samples were taken from my ear. Apparently by squeezing as hard as possible and making it look like I’d been punched repeatedly by Anthony Joshua). This was to determine the reliance on carbohydrate as a fuel, which could then be used to determine pacing and fueling requirements. Secondly, ‘performance’ was measured using power output (on the bike), perceived level of exertion and heart rate bike to understand if a ‘drop off’ in intensity occurred at altitude.
The amount that blood ‘desaturates’ of oxygen during exercise can provide some indication as to how well one can physiologically cope (i.e. maintain VO2max) when competing at altitude. Some research suggests that although there is not a definitive oxygen desaturation ‘threshold’ established, athletes who desaturate more than others will likely be more negatively affected at altitude. From various sets of data collected in published research, it seems that desaturating beyond ~90 – 92% is approximately the boundary that separates athletes between being able to maintain their VO2max well or not so well at altitude. My data showed that I did desaturate <90% during the altitude chamber session towards the end of the run, although for the bike and the first part of the run I was only marginally below.
The overall conclusion was that I responded fairly well overall to altitude exposure, and with a sensible pacing strategy and adequate nutrition I would hopefully cope well competing at altitude. However, as altitude can increase the rate of dehydration due to increased ventilation, and with my sweat rate being fairly high anyway it was worth planning for a higher impact. Variations in temperature, clothing or wind speed could also influence that rate so it was key to ensure that my drinks had adequate levels of carbohydrate and sodium to cope given the long duration of the event.
Awesome, so I don’t have some ridiculous reaction to altitude. Just the 10,000 feet of climbing to worry about. Bonus.