IF based on HR (Trainingpeaks)

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  • #38026


    Thanks for this great forum! I am using Trainingpeaks since reading TftUA a year ago. Neither testing, nor the internet, nor the trainingpeaks Support could help me understand the following about the intensity factor (IF) calculation:

    [IF running] = [pace] / [threshold pace]

    Why is

    [IF heart rate] not [average heart rate] / [threshold heart rate]?

    Are you guys able to understand how the intensity factor of your workout is calculated if you choose TSShr?


  • Inactive
    Anonymous on #38119

    I’ve never looked into it, so I’m not sure. However, I also never pay attention to the intensity factor. I don’t think it’s very useful in a heart rate focused program. (It may be useful in a power-based program.)

    Reed on #38126

    With a power meter on a bike or a run on roads, it’s not too difficult to measure rapid changes in effort – for example, a sprint or a hill climb. The TrainingPeaks calculations for rTSS and power-based TSS rely on normalized graded pace, normalized power, etc. The heart rate response to that acceleration will be delayed at best, and might not surface much at all. If you’re doing a sprint workout and have your AnT pace dialed in, rTSS might be more accurate.

    I generally find that TrainingPeaks calculates zone 1-2 runs as 0.60 to 0.70 intensity factor and roughly 40-50 TSS per hour. Intensity factor is interesting but hasn’t been that useful for me either.

    Estimating Training Stress Score (TSS)

    Alex on #38159

    Hi Scott and Reed,

    Thank you for the replies!

    I agree with both your comments and have been through all the resources I could find regarding TSShr, so I also know the pitfalls.

    Nevertheless I want to understand how the IF is calculated when using heart rate. It should be rather straight forward, but it’s not.

    Anybody has any ideas?



    Anonymous on #38194

    Not sure, but why do you care to know the calculation of a useless metric?

    As Reed described, easy activity is usually in the 0.6-0.7 range and, because of heart rate lag and upper-value limitations, I.F. will always fail at capturing intensity.\

    …unless you like math for fun. And both Reed and I would sympathize with that!

    Alex on #38315

    Hi Scott,

    what are the upper-value limitations?

    Regarding my motivation:

    The IF determines TSS. TSS is important and the Uphill Athlete recommendations go through great length to adjust TSShr for weight, downhills, etc. Understanding the calculation will help me put it into context.

    Originally I stumbled on the topic because my running TSS would never match my hr TSS, even when doing low intensity constant effort on flat ground.

    The formulas for running TSS are public, for hr TSS the support dodges the questions.

    By now I’m closed to convinced that there is conspiracy going on to hide the fact, that the calculation is wrong šŸ˜‰

    Anybody got an idea?



    Anonymous on #38336

    what are the upper-value limitations?

    Sorry for the confusion. What I meant was that heart rate can never adjust to reflect output. If you put out 300% of aerobic threshold pace for five seconds, your heart rate will not go up to a value that is three times your aerobic threshold heart rate.

    So that makes IF immediately useless, at least as it was originally designed for use with power.

    the Uphill Athlete recommendations go through great length to adjust TSShr for weight, downhills, etc.

    We do that because IF is irrelevant… IF has no bearing on our adjustments.

    By now Iā€™m closed to convinced that there is conspiracy going on to hide the fact, that the calculation is wrong

    You’re correct. The calculation is wrong because it can never be right. Heart rate doesn’t measure intensity; it measures stress. And it’s a limited system because it has such a constrained range.

    Reed on #38674

    If you really want to back into TrainingPeaks’ calculation of a “wrong” and not super relevant metric, you can! Add a 1-hour run workout to TrainingPeaks, and then add in a value for average heart rate. When you hit “Save,” it’ll fill in a value for TSS and IF. Plug and check, just like high school math. I eagerly await your findings. šŸ˜‰

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