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Svenne Vangoethemd

Hi Joe, first time that i post something on your blog but reading quite a long time now. I'm following your training principles from the bible and i just have the 'feel' to let you know that i love your way of training principles and it gives me a deep insight in training. As it's a very personal and difficult process, i just love to read your blogs and books. Thank you for reaching my goals in this wonderful life of sports and in particular cycling. Keep the good work on!


Joe, referring to Aerobic Threshold. In this post you state it to be approx. 30bpm below Lactate Threshold however in a previous article you wrote it was suggested as 20bpm less that LT. I subsequently had a rider train most of his Winter base miles at this intensity, which he went very well off! Can you explain why the difference.

Many thanks, Frances

Joe Friel

FrancesNewstead - 20bpm was an error on my part. 30 is correct. My apologies.

Stefan Gründel

Joe, in http://home.trainingpeaks.com/blog/article/joe-friel-s-quick-guide-to-setting-zones you suggest to do a 30 min time trial and take the average HR of the last 20 mins as approximation of your LTHR.

Here you're saying to take 95% of average HR, and this seems to be what TrainingPeaks platform also does when importing such a workout (I did a workout with an average HR of 177 for the last 20 minutes, TP sent me a threshold notification of 168 which is 95% of 177).

Can you please explain?

Joe Friel

Stefan Gründel--If you do a 20 min test subtract 5%. Otherwise, for 30 min as you suggest.

L. Steve Varnum

Hi, Joe, I am a 78-year-old rider. (We have communicated recently.)
I know this is an old post, but I am confused about the estimate for AeT using Aerobic Capacity. (I had the same confusion when I read it in "Fast After 50.") I thought it might be due to my age and my "numbers" being so much lower: Max HR is 147 and LTHR is 125 (fairly sure).
70% of MHR = 103
80% of LTHR = 100
LTHR - 30 = 95
All these numbers are fairly close. I have been using 103 as my AeT.
I understand the meaning of all the terms. I also am sure I understand AC and VO2 Max are for all intents the same (AC measuring O2 and VO2 measuring blood levels).
But since I don't know what my AC is, I thought I would back into it by dividing 100 by 60% but that yields 167 bpm – well over my max.
What am I missing?

Joe Friel

L. Steve Varnum--Thanks for your comment, Steve. You can't use a formula to determine what your heart rate is at any given physiological reference point. It simply don't work for individuals. The only time it will be close to accurate is when predicting what the middle of the bell-shaped curve will look like for a large population of people. And since we don't know where a given person is on the curve it's entirely useless for individuals. Your max heart rate is about where your AC heart rate will be found. But this is fairly useless info also as even if you do try to do, say, intervals at AC using heart rate as a gauge of intensity, it won't work as heart rate responds rather slowly and AC intervals are quite short. The interval will be over before heart rate gets up to a high level. Better to use perceived exertion on a 1-10 point scale.


I am still confused by the AeT section. You estimate that AeT is:
60% of aerobic capacity
70% of max heart rate
80% of lactate threshold.

If my AeT is 100 in this formula then:
AC is 167, MHR is 142, LT is 125
which is impossible. Joe, can you clarify please?

Joe Friel

Wphamilton - Just subtract 30 from your functional threshold heart rate to get a general idea of where it is. All of this is just estimates, not even close to precise measurement. If you really want to know for sure get a lab test done.

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