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Question about TSS vs hrTSS

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Question about TSS vs hrTSS

Old 03-18-21, 06:31 AM
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Question about TSS vs hrTSS

My understanding is that hrTSS tends to be a less accurate measure of overall workout stress when a workout includes a high amount of variability, such as VO2max workouts, but I am curious about comparing the two during steady state workouts.

What I am trying to understand is, if I take a steady state hour after warming up where I am at the same effort for the entire time, should hrTSS and TSS effectively be the same, and if they are not, is that indicative of something? If hrTSS is lower than TSS for a steady state hour, does that mean that my effort was not as hard as my threshold values would project it to be? If my hrTSS is higher than my TSS for a steady state hour, does that mean that my threshold is too high?
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Old 03-18-21, 10:13 AM
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Yes, it can be indicative to a whole host of factors, some that may or may not be controllable.

If it's a hot and humid day, hrTSS can be significantly higher than TSS than on a cooler day. I can do 300 watts for an hour and average 155-160 bpm in the winter, versus 170-175 bpm in the summer. 70+ dewpoints = skyrocketing heart rate.

If you're doing the workout multiple days in a row, hrTSS will likely start to trend lower as fatigue accumulates. If I'm doing multiple days of 300 watts for various durations, the second and third days heart rates will be 10-15 to even 20 beats lower than the first day.

If you're glycogen depleted versus topped up, hrTSS can be lower. If you're dehydrated, it can be higher. If it's morning, it can be higher, if it's afternoon, lower, etc., etc.

Last edited by rubiksoval; 03-18-21 at 10:18 AM.
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Old 03-18-21, 10:46 AM
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hrTSS tends to be closer also the less variability, in other words riding in erg mode on an indoor trainer.

Outdoors, I found before owning a meter for my gravel/cross bike that my hrTSS was inflated by it reading some level of hr while I was going down a little 20second hill. Well, that's 20 seconds of zero power output. Your hr probably won't recover enough in 20 seconds to cause the averaging used to get hrTSS to match what power based TSS would do there.

So, consider that also.

Also, hrTSS can be junk if you run and bike and have a "stronger" sport. Your weaker sport you'll have the heart and lungs for it, but not the legs. Therefore your hrTSS might be junk low and not reflect the actually training stimulus at all. This statement only applies to me, I can't speak for others. Just what I've seen.
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Old 03-18-21, 11:09 AM
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That's an interesting question. I use both HR and power on the bike though I haven't paid too much attention to differences, mostly because my HR is right about where I thought it should be when I do power-based workouts. I record all my workouts in TrainingPeaks, so it has both HR and power results.

I went back and looked through my workouts for the last few months, looking at both steady state and intervals. The one case where hrTSS matched TSS was when I did an Hour of Power type of workout, holding power near FTP for as long as I could. There, my HR came up to LTHR, matching my FTP very nicely, which is what one wants to see. In all other cases, my hrTSS was consistently lower than my TSS by 5%-10%. One might think that's just because HR always lags behind power, but this was true of both intervals and 2 hour steady state endurance rides.

I think the standard formulas for setting zones by percentages of LTHR aren't quite correct in the case of my current physiology. IOW, my heart rate is lower than the creators of these standards expect it to be. The may be because of my age, or it may be because of my many years of aerobic training. My current average morning resting HR is 48 and my standing resting HR average is 54.

So thanks for bringing this up. I'm going to go back through my HR settings and drop my zone boundaries down by a little. I'm not sure that'll change anything because I don't know the formulas TP uses for their HR calculations. TP only shows an IF for power, not for HR when I use both, but on HR-only workouts, like runs and hikes, it does show an IF, so maybe it records a HR-based IF for both, but only shows the power one if I'm using both. So maybe changing my HR zone boundaries won't do anything to change this situation, not that it really needs changing. Still, it would be better if my HR-based training were more aligned with my power-based training.

Everything rubik says above is true for me also, but the workouts I was looking at today were all indoors and all at the same temperature. Fatigue was a small factor. If I'm fatigued, it takes a little longer for my HR to come up, but it does some up to normal all the time, so far. I think that's because I'm not letting myself get too far in the hole, i.e. TSB not much below -10. I'm seeing consistent results.
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Old 03-22-21, 09:56 PM
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My Friday/Saturday/Sunday rides last week had a TSS of 102/104/106 and a RE (Relative Effort fun Strava. Based on HR) of of 208/42/49.

Big difference in those RE numbers! The 208 was 59:58 at 99% of FTP (low variability) and a short cool down on Zwift. House was cool and I had a fan so heat was less of an issue than normal.

Ride two was 2.5h on a MUP with 25min rest at 61% of FTP (again low variability). Temp was cool and not an issue.

Ride three was a leisurely 100km for 4h45m with 30min rest at 46% FTP (normalized) with modest variability (41% avg. FTP)

For me, hard rides with efforts, especially sustained efforts, anywhere near FTP will have massively higher RE based on HR. Rides 2 & 3 has almost no time riding hard. Ride 3 had 63s in Zones 5-7 and Ride 2 had 64s so my HR never became elevated.
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