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Old 01-22-21, 09:49 AM
  #11  
RChung
Perceptual Dullard
 
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Originally Posted by Branko D
If your starting point is 3.2W/kg and you are 19, my feeling is you could get to 4W/kg in a relatively short period of actual training which is pretty good.
Maybe. We don't know enough about the OP's situation to know for sure, but getting to 4 w/kg "in a relatively short period of actual training" isn't alway possible.

We have the Golden Cheetah Open Data project, which allows us to examine power data for thousands of athletes. This gives us a better idea of the range of power among riders who are serious enough to use a power meter. Unfortunately, we don't always know their weight but from what little we do know it appears relatively few would have an FTP as high as 4 w/kg. So, since we know so little about the OP's background, perhaps he can easily attain 4 w/kg but simply being at 3.2 w/kg today, 19, and a beginner is no guarantee of that.

Here's a quick approximation. Greg Lemond famously claimed his VO2Max was 92 ml/kg/min while Armstrong's was "only" 85. But more importantly, we know that many "normal, regular" athletes will tend to top out near a VO2Max of ~ 60 ml/kg/min. We also know that, ballpark, FTP is in the neighborhood of 80% of VO2Max (that is, VO2Max is 1.25x higher than FTP). Finally, we think that cycling economy tells us that it takes, on average, around 1 L/min of oxygen to produce 75 watts. You can substitute different values for these if you want but if we use these estimates, we can get a rough estimate of FTP for an "average normal regular" rider of (60 ml/min/kg) * (0.8 FTP/VO2Max) * (75 watts/L/min) = .06 L/min/kg * 75 W/L/min * 0.8 = 3.6 W/kg. Coincidentally, at my best, I topped out at 3.7. (Maybe you can see why I'm familiar with this approximation).

Perhaps a rider can do slightly better than these, and can top out at 65 ml/min/kg, and can attain a slightly higher ratio of VO2Max to FTP of 1.2 (i.e., ratio of FTP to VO2Max of 0.8333). Then, approximately, we'd expect that rider to max out at .065 * 0.833 * 75 = 4.06 w/kg. But I'm not sure that would be quick, or easy, cuz I never got there.

[Edited to add:] BTW, oxygen comprises about 21% of normal atmospheric air, so if it takes 1L/min of O2 to produce 75 watts, you need to breathe in around 5 L of air to produce 75 watts. The average sized adult male has a lung tidal volume of around 0.5 L, so just to exchange enough air to produce 75 watts, you need to inhale-exhale about 10 times/minute. To get enough air to produce 225 watts, you'd need to inhale-exhale about 30 times/minute. These are all ballpark figures, so if your tidal volume were larger (and your lungs were better at exchanging CO2 for O2) your respiration rate could be lower.

Last edited by RChung; 01-22-21 at 10:07 AM.
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