Monday, November 19, 2007

0 Altitude and cycling world hour records

Why were most hour record locations at altitude?

At high altitudes, aerobic capacity decreases since atmospheric pressure and the partial pressure of oxygen is pretty low. This is because atmospheric pressure decreases somewhat linearly with height. So does density of air, or the number of air molecules packed in a cubic feet or whatever unit of volume of air you want to consider. In aerodynamics, lift and drag depend linearly on density of the fluid (air in our case) So if density if going to decrease with altitude, so is the drag or wind resistance. Air density is a direct multiplier in the equation for drag!

Which is why (well, not entirely the reason but it counts in), most venues for famous hour records (Eddie Merkcx etc) were located at altitude, so the cyclists would have to face lesser drag than at sea level. Chris Hoy's recent attempt at the kilo record was, according to PezCycling News, was venued at some stadium in Bolivia, which is 3500 feet above sea level. Wow! If you play around with this applet on a NASA website, you'll see how such an altitude change affects barometric pressure, and air density (consequently, drag). Click here for density effects on drag (its for the wing of an aircraft but you'll get my point).

Another epiphany I had. Tail winds might not help THAT much at altitudes. :)


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