That was the gist of what I thought I read, but I’m also working on 3 legal contracts, negotiating some project stop/restart dates, and generally Monday distracted. So maybe its all in my mind!!!
I didn’t read that in the OP, just that they didn’t know what to do when their HR was 20 bpm above their usual level for the steady power output. Don’t think they mentioned hydration at all.
it was the recent posts discussing, not the OP.
Just to keep things on track, and a thought that occured me.
Those are my real numbers: 295 ftp, 200w is a the upper part of my endurance rides, 185 being the ideal without accumulating fatigue and being able to do it repeatedly. 135 BPM upper limit, comfortable at about 130BPM.
FORGET THE REASON, I’m curious about the effects:
If I start a ride at 200w ~130BPM. After 1hr I’m able to keep 200w as it’s not hard, but my HR went up to 150 - again, forget the reason. In this case my HR in on tempo, while my power is in endurance. What am I doing physiologically speaking?
In 2019 these were exactly my numbers, exactly 
Never happened to me.
You sure? That big of a jump is telling you something.
Ok, so we’re doing a thought exercise. Cool.
In terms of adaptations? Nothing. Same as scenario in which HR doesn’t increase. In terms of fatigue, for some reason (but we’re not paying attention to that) seeing more strain on your body.
Nice!
It never happened to me. Usually my cardiac drift - to be accurate I think that’s the name - is quite low ~2%
But the point is, I’m not at endurance anymore, according to my HR, although my output is still the same.
I guess it wouldn’t be as repeatable as it should.
This just happended to me when I started indoor riding last week. I don’t have sufficient airflow where I train, so the heatsoak is real. During a Zwift race of 1hr, the first 20mins my hr+power numbers were pretty okay/normal. The final 20 mins were anything but, new season highest hr for 20mins at 172bpm (~188max).
I attribute this to lack of cooling, but otherwise I would be pretty concerned 
This right here is the key.
Due to the ubiquity of HR monitors over the last 40 y, many people suffer from the misconception that the frequency at which your heart contracts somehow determines the adaptations to exercise. As you astutely point out, it doesn’t - rather, it is merely a response, reflecting (to some degree) the degree of cardiovascular strain.
To give an example: you have a sleepless night, which messes with your body fluid balance, reducing your plasma volume. As a result, your HR while exercising is, say, 10 beats/min higher than usual. Do your muscles (where the most important adaptations to training take place) care? No, not really. Does your cardiovascular system even care? Probably not… it’s job is to generate pressure to drive cardiac output/maintain blood flow, and it has lots of levers it can pull to compensate for small variations in, e.g., CVP.
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Hard disagree here. You like to point out the exceptions, the biases of HR. Fine, but over looong samples, comparing say year to year a rider that is getting fitter will see lower heart rate per watts.
Go plug your data on Intervals.icu and check their default plot, which also incorporates cadence.
How many 1m avg HR and Pwr do you have in 1 year?..…Say 500h x 60m = 3000m. That’s enough for the law of large numbers to do it’s thing.
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WKO, since it’s the Cog. LOL
Kidding aside, I remember many riders posting in the ISM, Lactate, and other related threads expecting this phenomenon to happen quickly (I would have too had I not been coached otherwise). Just something to bear in mind, as it is not something I would rely on to answer “how much fitter am I in six weeks”.
For this you are better off with the infamous CTL
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This year for myself
- FTP 270-280W
- 142bpm HR at my perceived upper limit for endurance riding (can do 142bpm steady power, but fatigue builds and impacts upcoming rides)
- repeatable endurance rides of ~2 hours (4 a week) my HR after 10 or 20 minutes is around 136bpm, and rises to 140-142bpm by end (usually negative split on power)
- 158-162bpm HR while surfing around FTP
Average HR for a lot of 120-minute rides (includes warmup, cooldown, and 100 minute endurance interval):
I’ve got better charts in WKO5, for example:
That show average HR/temp for (in this particular chart) the 60-minutes of interest. For example that first endurance ride is showing average power/HR/temp for the 60 minutes starting at 50 minutes into the 126 minute ride.
Physiological speaking for myself, when my HR shoots up into the 140s or even 150s, its because of early exposure to heat at 90-100F / 32-38C. Heat stress. Heart needs to pump faster for cooling and stuff. And I’ve learned that heat stress generates a lot of fatigue, so I reduce power and “ride by HR” keeping under 140bpm while acclimating. And that reduces fatigue, and I can keep riding an average of 8 hours/week. For myself its about heat stress and fatigue management.
Probably doesn’t help you, but thats what I’ve seen in my own training.
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Very interesting analysis, as well as evolution. I don’t have past power numbers to compare, and that’s one reason I’m so used to HR. I trained several years only based on HR, so I know where is my endurance pace.
Your numbers show a interesting trend as well. You’re putting more power with the same BPM, which underlies the point of HR being an interesting tool during exercise and metric as a whole.
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My endurance pace HR is from when I trained by HR, and refined over time. Some info on my field testing here:
and threshold HR here:
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So?
A decrease in HR at the same absolute intensity of exercise is a well-documented cardiovascular adaptation to endurance exercise training.
However, that’s not the question - the question is whether altering training intensity in response to acute variations in HR results in greater improvements in fitness over the long term. There is no evidence that is true, nor any sound physiological reason to expect it to be true. The latter is doubly so since muscular metabolic fitness, not cardiovascular fitness, is the primary determinant of performance.
TL,DR: what matters is what you actually do, not why you decided to do it.
Wouldn’t this all be resolved if people starting riding “endurance” by RPE and ignoring power and HR?
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As I am sure you know, it does happen quite quickly, at least in initially untrained individuals:
Of course, the fitter you become, the more difficult it is to make further progress, which in absolute terms makes it seem like the time constant/halflife of adaptation has slowed down.
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Not just endurance, but at all intensities.
PPP: It’s called training with power and not training by power for a reason.
PPP: If it feels hard, it is hard.
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My zone 2 training is literally to fill in the low aerobic bar for my Garmin. If the workout is pushing my average HR to 80% of HR max then I’ll either reduce the intensity or if I know the workout is going to do that I’ll just pick an easier workout.
Hi OP! I didn’t see it mentioned. How did you determine your HR zones?
120-130 with a max of 185 could totally be endurance.
It’s best to do a lactate HR test or variation. TrainingPeaks has some stuff to read up on, or the books by friel.