When is IF .86 not IF .86? Diagnostic question

Hello brain trust,

I just finished a VO2 max workout of an hour w an IF of .86. It was quite manageable. SS workouts at that IF are likewise hard but manageable. But a threshold workout at that IF KILLS me. I’m trying to diagnose what that means. Good cardio but bad leg strength? Etc. Thanks for any wisdom you might be able to provide. Assume it is not related to diet or rest, as the pattern is old.

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IF on it’s own is only part of the story. Duration of the total workout is key.

  • 0.86 IF at 30 mins vs 90 mins are two very different things.

Couple that with the type of efforts (and where they relate to your fitness strengths / weaknesses) and the recoveries. You can have identical IF with 60/60 On/Off vs longer steady state intervals. Each of those may be better or worse for different riders on different days.

Essentially, it’s difficult to capture the relative difficulty of any workout with a single number, IF included.

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Ah, I see. Thanks, that makes intuitive sense. But it remains the case that I am much better at SS than threshold, even when duration, recovery, nutrition are held constant. Is it possible to assess what that represents vis-a-vis training deficits? Or is performance simply too idiosyncratic to know without personalized testing and evaluation?

But what kind of threshold workouts? Because looking at the library IF > .86 can be the workout like Darwin or Galena, so then your stamina and muscle endurance is a problem or supra-threshold workouts like Elephants - then probably muscle endurance and lactate tolerance or over-unders - lactate tolerance and clearing rate and muscle endurance.

The best solution (that was in my case) is to do more of these type of workouts that causes you a problem :slight_smile: When I was doing Darwin for the first time it was one of the hardest workouts I have ever done, the same with Galena+1.

Second case is with long and steady workouts near threshold the proper fuelling and cooling are the most important part in my opinion.


Thanks, this is really thoughtful. I guess it really is true what they say: train your weaknesses and race your strengths.

Outlook for iOS

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It also is a reminder to be aware of the limitations of any metric.

Here’s an easy example: go out and do a workout that absolutely shatters you for 30 minutes. Something truly awful. IF will be 1.05 or maybe even higher. Really bury yourself.

Now keep spinning at a breathe through your nose pace for an hour.

You just made your IF less than 0.7, but you’re still wrecked.

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Yes indeed, another good reminder. The moral of the story, which I probably should’ve figured out myself, is that training is complicated and cannot be reduced to simple measurements in isolation from the whole package, whether they be total time in the saddle, HR, TSS, IF, etc., to say nothing of the way these all interact with each other, and with rest and nutrition. As I write that sentence, I see how self-evident it is, yet I still found (and still find) it curious how I can be adapted to one type of workout so much better than another. Thanks.

One very important thing is it also simply comes down to physiology and what ‘kind’ of rider are you. Genes and body build has a big part to play here as well.

Case in point, below are examples of this weeks workouts, both an hour long and both at the same intensity. One was a VO2 workout (Monday) one was a threshold workout (Wednesday).

As a big dude, with really good short power I can do a VO2 workout with ease. But give me a threshold workout and I will want to jump out a window within the first 30 minutes (compare my max hear rates, I nearly died during the second workout) :joy::joy:


Well said. Your snapshots really make the point. Thanks.