I just started using intervals.icu, which is a great project. Thanks for your fantastic work!
I am wondering, if the calculus of the FTP and FTHR is correct after doing a 20-minute HR test. I noticed that you simply take the average power and HR for the 20-minutes. This is as linked in the blog article from 2009 from Joe Friel. However, there is an updated calculus, for which a 5% margin is subtracted, probably to correct the 20-min load to match the 60-min better. This is described in Joe’s latest edition of his bible (4th) and also here:
Could you maybe add an option to take the 5% into account?
Tx. Intervals.icu currently uses 98% of 20m HR for LTHR. This was derived after some discussion on the forums. Maybe you could just knock a few bpm off? You shouldn’t get too may false “LTHR up” notifications.
Good to know that it is 98% of the LTHR. Does this also apply to the FTP value?
For my single FTP test, I did a manual analysis of the 20-min section and it seemed that for both power and HR 100% of the average power and HR were used. But I could also be wrong as the 98% could be within the tolerance of the definition of the FTP interval segment.
For sake of completeness and clarity, it would be nice to describe the calculus in the info box as both values represent crucial metrics, from which the training zones are derived.
It’s worth remembering the FTP test comes after a very intense FTP warm up. The whole process takes an hour excluding cool-down (Training & Racing with a Power Meter Ed 3 refers). It’s important to eliminate the anaerobic energy system from the aerobic effort.
Separately, there is also a protocol for LTHR following warm up, with a thirty minute effort from which the final 20min ave is taken as the LTHR.
I see that a FTP test is in fact prepended by a proper warm up and anaerobic power elimination phase.
I rather was pointing to the fact that intervals.icu does not seem to subtract a margin from the average HR to get the LTHR. The FTP is fine, sorry for the confusing comment concerning that.
Average power 253W*0.95=240W → eFTP also estimates 240W, which is fine!
Average HR is 160bpm. If I leave out the ramping up phase it is 159bpm, so just running a 20-min FTP is fine (which Joe Friel recommends in his 4th Ed and in the link above).
If I now hit the Update Zones button, my LTHR in Settings->Run->Threshold HR is set to 160.
No. The “standard” accepted value is 92, but may be anywhere between 90-95% depending on the athlete. Trevor Connor is very clear about this point. I don’t remember which episodes he specifically goes into this, but just start with the first listed on this (You searched for ftp - Fast Talk Laboratories) page and listen to them all.
If an athlete truly wants to know their LT1/VT1 and LT2/VT2 then do a search for Dr. Stephen Seiler and read & listen to everything available.
I think you are interpreting that in the wrong way. When you click on Update Zones, that will apply the zones from the settings page to this specific workout and not the other way around. The purpose of that function, is to apply new zone settings to the workout that was already processed with the older settings. So the treshold HR in settings is not set by this workout, but it is the other way around.
Unless you had a new Treshold HR detected by the original analysis in the same way that intervals detects a new FTP. Then you can accept that new value and update the settings with it.
I hope this explanation makes sense, because it is rather difficult to clearly eplain…
thanks for the link to the podcast episode, indeed very interesting! It is a great podcast to get insights from some well-known experts, perfect for some indoor cycling sessions!
