Tuesday, January 13, 2009

Heartrate and VO2max Predicts Cycling FTP

In my research of the relationship of VO2max and max potential FTP, I stumbled on this calculator: http://www.braydenwm.com/calburn.htm.

I've seen lots of littel cutesy calculators like this; but for fun I input my data: male, 150 lbs, age 40, ave HR (at FTP) 162 bpm, VO2max = 70 ml/kg/min. I was quite amazed to find that it predicted my power output at FTP (based on average heartrate) to be 290.46 watts. My last two FTP test results are 290 watts and 292 watts.

Either this is a really cool coincidence, or there is some good science in the paper on which the calculator is based, found at http://www.braydenwm.com/cal_vs_hr_ref_paper.pdf. I haven't read it yet, but I will.

This is the formula used in the calculator:
kCal/min = (-59.3954 + (-36.3781 + 0.271 x age + 0.394 x weight(kg) + 0.404 x VO2max(ml/kg/min) + 0.634 x HR(bpm)))/4.184

I don't know what each factor means yet, but I probably will after I go through the research paper.

Calories burned vs oxygen intake is relatively well understood. Oxygen intake is commonly measured (it's VO2max). And I know that the calculator assumes a 24% efficiency from chemical to mechanical work for cycling, which is a commonly-used and accepted factor (it usually ranges from 20% to 25%).

Now if I can find good data relating FTP and % VO2 max for elite cyclists, I should be able to set up a direct relationship between VO2max and FTP in well-trained cyclists. This would be the relationship that LeMond is proposing to use in evaluating power output of riders in the pro peloton to test for doping.


Colin Griffiths said...

That's very interesting, even if it only turns out to be so only for entertainment purposes only. I would be interested in any follow ups as well. Had you thought about posting it on the Wattage Forum?

Robert Jordan said...

So far the VO2max/FTP relationships I'm developing are just what you said: "for entertainment purposes only." There are so many difficult-to-define variables involved, that I'd get ripped to pieces on Wattage at this piont. Maybe I'll consider posting there if I can develop a firmer foundation for the numbers. I'll never develop an equation that will predict any one person's FTP from their VO2max. What I'm hoping to do is use the high extremes of each variable involved to determine a physiological 'ceiling' for FTP as it relates to VO2max. That's a much more realistic goal, I think.

Anonymous said...

Thanks for this treasure. I can guarantee you that a VO2 Max of 78-82 will never yield you an FTP of 450+ watts. Ahem, Ahem. Thanks Lemond for being completely forthcoming with us.