Your book and information at this website are THE reference for running with power besides Jim Vance’s book. I really appreciate that finally the ‘full physics’ of running are explained in a comprehensible way in one reference.

However, I wonder about your assumptions in the online calculator regarding FTP and VO2max, understanding that you derive VO2max from FTP by the factor of 0.072, here.

I end up with a calculated FTP that agrees well with my STRYD CP, but VO2max (using the aforementioned factor) does not agree with that calculated by the Jack Daniels formula, whereby the latter actually provides me with very good estimates for my duration-dependent race paces.

Should your calculator not rather use the factor 0.081 to derive VO2max from FTP (as stated in Chapter 75 of your book) instead of 0,072? At least for me, this provides a VO2max estimate which is closer to that calculated by the Jack Daniels formula (-> realistic race time estimates).

After doing some further testing with the calculator and my own calculations, I understand that you are scaling the factor to relate VO2max to FTP by 10 min to 60 min, even though race times provided by the user are likely always different.

Hence, you receive different VO2max values for race paces that actually perfectly match the calculations after Peter Riegel. Scaling the factor by race time vs. VO2max time solves this issue from my point of view. Consequently, each realistic pace for a given race distance would provide the same VO2max value.

I am looking forward to your comments and would be grateful about more details on your calculations.

Thank you for your compliments and question.
I am glad see that you have figured out the answer by yourself already….
Indeed, we calculate the VO2max from the given race pace for a given distance.
The relationship between FTP and VO2 max is the factor 0.072.
This can be easily understood by the different duration times (FTP= 1 hour and VO2 max= 10 minutes, the Riegel ratio is 0.88).
The relationship between FTP and VO2 is theoretically a factor 0.081 as explained in chapter 75.
So the VO2 at 1 hour FTP/0.081, consequently the VO2max at the FTP is FTP/(0.081*0.88) which equals FTP/0.072

Thank you for the book! I’m enjoying reading it. I’m not following a following in Chap 20 where you relate FTP and Vo2max. Vo2max is expressed in ml/kg/min and DeltaG in KJ/L of O2, it seems than when doing the conversion, we should end up with Vo2max in L/kg/Min vs. ml/kg/min? could you help me there? thx L

Hi Laurent,
Thanks for the question and we are happy that you enjoy reading our book.
The answer is that delta G is indeed expressed in kJ/LO2 which is equivalent to J/mLO2.
So you can convert the VO2 max in mlO2/kg/min to 0.25*19.55J/kg/min.
As 1 Watt is 1 J/s, you also have to divide by 60 (seconds in 1 minute) to come to Watt/kg which is the unit of the FTP.
Best regards,
Hans van Dijk

Dear Hans and Ron,

Your book and information at this website are THE reference for running with power besides Jim Vance’s book. I really appreciate that finally the ‘full physics’ of running are explained in a comprehensible way in one reference.

However, I wonder about your assumptions in the online calculator regarding FTP and VO2max, understanding that you derive VO2max from FTP by the factor of 0.072, here.

I end up with a calculated FTP that agrees well with my STRYD CP, but VO2max (using the aforementioned factor) does not agree with that calculated by the Jack Daniels formula, whereby the latter actually provides me with very good estimates for my duration-dependent race paces.

Should your calculator not rather use the factor 0.081 to derive VO2max from FTP (as stated in Chapter 75 of your book) instead of 0,072? At least for me, this provides a VO2max estimate which is closer to that calculated by the Jack Daniels formula (-> realistic race time estimates).

Thanks your comments and kind regards,

Thomas

After doing some further testing with the calculator and my own calculations, I understand that you are scaling the factor to relate VO2max to FTP by 10 min to 60 min, even though race times provided by the user are likely always different.

Hence, you receive different VO2max values for race paces that actually perfectly match the calculations after Peter Riegel. Scaling the factor by race time vs. VO2max time solves this issue from my point of view. Consequently, each realistic pace for a given race distance would provide the same VO2max value.

I am looking forward to your comments and would be grateful about more details on your calculations.

Thanks, Thomas

Dear Thomas,

Thank you for your compliments and question.

I am glad see that you have figured out the answer by yourself already….

Indeed, we calculate the VO2max from the given race pace for a given distance.

The relationship between FTP and VO2 max is the factor 0.072.

This can be easily understood by the different duration times (FTP= 1 hour and VO2 max= 10 minutes, the Riegel ratio is 0.88).

The relationship between FTP and VO2 is theoretically a factor 0.081 as explained in chapter 75.

So the VO2 at 1 hour FTP/0.081, consequently the VO2max at the FTP is FTP/(0.081*0.88) which equals FTP/0.072

I trust this will be clear now?

Best regards,

Hans van Dijk

Thanks for the prompt reply, Hans.

Thomas

Hello Hans and Ron,

Thank you for the book! I’m enjoying reading it. I’m not following a following in Chap 20 where you relate FTP and Vo2max. Vo2max is expressed in ml/kg/min and DeltaG in KJ/L of O2, it seems than when doing the conversion, we should end up with Vo2max in L/kg/Min vs. ml/kg/min? could you help me there? thx L

Hi Laurent,

Thanks for the question and we are happy that you enjoy reading our book.

The answer is that delta G is indeed expressed in kJ/LO2 which is equivalent to J/mLO2.

So you can convert the VO2 max in mlO2/kg/min to 0.25*19.55J/kg/min.

As 1 Watt is 1 J/s, you also have to divide by 60 (seconds in 1 minute) to come to Watt/kg which is the unit of the FTP.

Best regards,

Hans van Dijk

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