Thursday, 30 April 2015

Calgary Half marathon

I'm running the Calgary Half marathon, May 31st.

Looking forward to it. Raced decently in Grande-Digue 15k last week. Flat(ish) course, cool weather and no wind helped too. Also having the Dal team there was nice boost. In total 8 guys under 50 min, which is something for a tiny race in northern NB. I other news our rag-tag team will be getting a little more serious as we're set to join Halifast.

Back to Calgary. Nice part about the Calgary 21.1k is their efforts to get people from all over Canada to take part. It's the national championships after all, but still impressive what they're doing. Strangest part about national-level road races in the past is the organizers inviting people, offering prize money/appearance fees etc but not posting anything interesting about them online. Often not even a headshot. I always wondered why go through the trouble of organizing people but not profiling them. No more!

Soon-to-be profile shot. Everyone gunning for a sub 74ish time gets one, and a 'fun fact', which is nifty. My fun fact is that I'm an atmospheric chemist. (guess they didn't go with my joggling angle!)
A race with altitude

Also, since the race is in Calgary, people have been worried about altitude effects. Calgary is roughly 1050m elevation, or about 3440 feet. That sounds like a lot, and it certainly would be a lot if the race started at sea level. But the race course is quite flat, as you can see below:

A very flat course indeed
Higher the altitude, the lower oxygen's partial pressure in the atmosphere. At 1 kilometer there is 88% of the oxygen available at sea level, which is not terrifically low. Much higher elevations lead to severely lower levels. Pause for a second to imagine what it's like to be a above 8000m, where oxygen is less than 1% of normal values.

So what happens to the body's oxygen saturation at 1000m? That's a function of both the available oxygen and hemoglobin's affinity to O2. Thankfully there's a website that's already calculated this for me at altitude.org.

Plugging in 1000m, we see the saturation of O2 is 97%, down from 98% at sea level. Why such a small drop? It is linked to the same reason we don't benefit from breathe pure oxygen. From Dr. Schwarcz:
Researchers studied professional soccer players who breathed either room air or pure oxygen in a double blind fashion before a period of exercise. There was no difference in performance and the subjects were unable to identify which gas they had inhaled.
Our body is over-engineered ever-so-slightly to handle slight decreases in available oxygen (on the order of a few percent), and our oxygen supply is limited by our blood-oxygen uptake (hence why EPO boosting does seem to work). Point being we can handle a little bit of altitude without much difficulty.

Altitude oxygen saturation at 1000m elevation as calculated by altitude.org. The oxygen partial pressure curve drops dramatically after 6kpa partial pressure (80% hemoglobin saturation) at 3500m
I conceded that less oxygen will certainly make some difference. There is a paper from Peronnet et al (1991) that actually calculates the theoretical effects at various distances and altitudes, (including Calgary!):


Peronnet's values indicate a marathon runner will lose about 4 minutes between sea level and 1000m, or about 3%. Keep in mind these are theoretical values, but neverthelss they seem realistic. I sort of wonder if they are exaggerated (given my experience with theoretical running models in the past)

What practical evidence is there that the elevation effects are small at this height? The best might come from the Calgary Olympic oval, which during the 1988 Winter Olympics a new Men's 10,000m and women's 5,000m record was set (among others). Later at Utah's Olympic Oval, with over 1,400m in elevation, skaters set new 10,000 and 5,000m records [fun fact: skating speeds are almost exactly twice running speeds]. Wind plays a much larger factor for skating than for running, hence a reduction in total atmospheric pressure is beneficial. But I suspect if these athletes were truly oxygen deprived such fast times would not be possible (a rink a 3km elevation is unlikely to set any distance records whatsoever).

My only conclusion is this: I'm hearing too many people worry about altitude. But it's such a small effect. Sure, 3% is measurable, but just within the margins of error. Meanwhile we know we're all racing the same race, so in the end it really doesn't matter. Until then, I'll make due with Halifax's sea level and lots and lots of tiny hills.

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