Why did IF change after compleded workout?

So yesterday I did Lion Rock. The IF for the workout is 0,83. Well that is what it says on the workout. My compledet workout says IF 0.81. Why is this?
I have noticed this on my latest workouts. On saturday I did Pierce, was suppose to be IF 0.85, but on my completed workout it says IF 0.82.
I did add some extended warmup, is that a part of the reason? 10min extra warm up, and 5 extra cool down.

Yes - the extra warm up and cool down are at such low intensity that they will make the IF lower.

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It’d be kind of nice if that didn’t happen. In fact I think that sometimes I avoid extending cooldown out of ego because I know it will reduce the IF.

Maybe the IF should refer to the work intervals only.

Hmm… For it to make that big of a difference dont make sense to me. It does not feel like the warm up makes that much ofadifference. For me I do extra warmup for injury prevention (not sure if this part makes a difference) and to get a easier mental start :yum:
Is it just the warm up that change the IF? Dont make sense if the extended cooldown count.

You’re extending the 90 minute workout by a whole 15 minutes, all at under 50% intensity… So i’d say it will certainly be normal for it to lower the overall workout intensity by 2 or 3%.

I wouldn’t worry about it, if you know you’ve hit the intervals correctly…


IF is defined as Normalized Power divided by FTP. If you extend the duration of your ride your NP will change (lower if you extend with riding below the average NP for the ride) and thus IF will change.

It’s easy to think that the workout was as hard as it would have been without the extensions, but you have to look at it based on duration. A 90 minute ride at 0.83 IF is obviously easier than a 105 minute ride at 0.83 IF. You did a 105 minute ride at 0.81 IF which, in your case, is harder than the former, but easier than the latter.

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Here’s Lion Rock in workout creator with extra warm up and cooldown. Suggests about 0.8 IF

IF is simply Normalised Power divided by FTP. If the Normalised Power decreases (by adding some low intensity work) then IF will decrease.

Seems like you are asking for a metric which gives your Training Stress a Score?

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What I’m saying is that most people take IF to mean “how hard are these intervals today?”.

And if you do like Alice did and add warm up and cool down, she’s not making the intervals in Lion Rock any easier. But if she goes back and checks the IF of her workouts, it’ll give a false impression of the difficulty.

There’s a big difference between doing that and adding low intensity work between the intervals, which obviously does make the workout easier.

It’s almost impossible for a single metric to capture how hard a workout is when comparing different types of workout. That’s why TR are constantly saying that “not all TSS is equal”. If you’re comparing similar types of rides (i.e. similar interval lengths or target zones) then metrics like TSS and IF are more comparable.

Thanks for your answers, know I know why.
I will just have to remember to check the source file of the orignal workout when I want to compare workouts. I like to mentally prepare myself for the next workout by comparing IF with previous finished workouts.

Intensity factor is not a good metric to look at without reference to time (which is what TSS does):

Imagine riding at your FTP for 30 minutes - that’s an IF of 1.

Now ride at FTP for an hour - that’s an IF of 1 also.

The first effort has a TSS of 50 and the second 100.

Going the other way, you need to ride at an IF of 0.71 (a normalized power of 71% FTP) for 2 hours to get 100 TSS.

It’s important to look at both to gauge difficulty.


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I get that, but… (with apologies for sort-of hijacking the thread)

…I think that time is a bit of a given? We know whether we’re looking at 60 or 90 or 120 minutes depending on what we’ve searched for, or what volume training plan we’re on.

And TSS is both flawed (30 minutes at 100% is the “same” as 60 minutes at 71% but I know which I’d rather do!) and hard to interpret instinctively.

Whereas when I look at IF, I can immediately get an impression of the difficulty. E.g “0.89 IF for 90 minutes, so that’s like riding sweetspot for 90 minutes, this will be hard”.

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