This has probably been asked and answered many times but… I check normalized power all the time after a ride to gauge my effort, and also check average HR. How come normalized HR isn’t a thing?

[image] Bbt67: even if yours changes very fast it is very slow and in a very narrow range compared to power. You are missing the big issue and that is: Avg HR for a session does not appropriately describe the effort. See my example of 2 diff workouts.

[image] Bbt67: but Normalised HR won’t either Normalization is a generic time series procedure, you can select the appropriate parameters that would make the desired output meaningful. The gist of op’s question, is why isn’t there a descriptive metric analogous to NP to capture the variable nature of HR. As I said before, I think it’s because HR as in bpm variance is different scales for different individuals.

[image] RonG: How come normalized HR isn’t a thing? My heart rate is self-normalized. And if my heart drops out, I’m not gonna give a farq about my activity data.

[image] Brennus: My heart rate is self-normalized mmm. You don’t understand normalization

It has to do with the stochastic nature of power compared to HR, as almost everyone has alluded to. I asked a similar question a few years ago (can’t find it right now. see below, @mcneese.chad found it), and someone proposed assessing the variability of HR during a single session using standard deviation. Obviously HR never goes to zero (so no need to normalize using a calculation similar to power) but it can vary in a hard group ride, long ride with variable efforts (hills, etc), races, stops, etc…and those are different than just “hold % HRMax for 3 hrs” (for example), even though the average HR for all of those can end up being the same. Also, even though normalized power is very useful, it’s still not strain. It is a measure of load (when considered over time). That’s only part of the picture. As imperfect as HR is, it’s basically all we’ve got (can’t measure cardiac output). So having a crude metric for how variable it was is better than nothing.

[image] tshortt: I asked a similar question a few years ago Is this it? Variability Index For Heart Rate

going back to basics, the guy (Dr Andrew Coggan) that created normalized power wrote a paper for a USAC coaches meeting. He gave a background, justification for levels, and when it came to analyzing power data he outlined limitations of using kJ work and time in zone (frequency distribution of power). His alternate approach was to leverage Dr Eric Banister’s TRIMPS work which for HR is duration x average HR x HR-dependent intensity weighting factor. So if you want a HR approach, go down the Banister TRIMPS path. I’ve never looked into the HR intensity weighting factor. Does anyone know how TRIMPS works w.r.t. HR intensity weighting factor? FWIW TrainingPeaks has a TRIMPS based TSS score - tTSS - that appears to only use duration and average HR. The TP hrTSS uses duration, average HR, and threshold HR which appears to be a nod to using some form of intensity weighting.

[image] oldandfast: This is the same average HR that I would get with a Low Tempo ride, but the spikes profile and the physiological cost are completely different. Not the global average, the average during the interval or set (when you do 30-30s or so). [image] oldandfast: I have a very reactive HR, goes up and down fast with hard efforts It is still reacting much more slowly and represents the average effort of your cardiovascular system within the last minute or few minutes. That means a weighted average of your heart rate will be not too different from the average, especially if you are looking at shorter durations. Instead, time-in-heart-rate zone or heart rate in power zone will likely contain more useful information.

Is it even useful to look at normalized power for a whole ride? I was actually just reading Racing and Training with a Power Meter the other day and the example they gave was looking at the normalized power of a 1 hour criterium or a 40k TT.

TrainerRoad

Why no Normalized HR?

Training

mcneese.chad April 4, 2023, 7:10pm 15

Is this it?
Variability Index For Heart Rate

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Is there still a use case for Heart Rate? (HR) Training	141	9806	July 18, 2023
Power is not definitive, it is a factor, the same as HR Training	70	3950	February 28, 2021
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Future Request: Pwr:HR ratio TrainerRoad Software	14	1707	December 16, 2018
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