Huh, it is in same ballpark indeed. Never knew 
I seem to unable to use talk test or nose vs mouth breathing to understand when crossing LT1 – when I get self-conscious, those patterns automatically change. I actually learned upper Z2 HR cap from experience, how frequently have lost motivation during season and only then put marker for myself (80% of LTHR or 60-63% of FTP). And when exceeding occasionally 24h+/week, then it is even lower, 57-60% of FTP.
In other words, go ride at threshold for a long time and see where your HR settles.
The idea is to give people the most robust, generalizable advice, not to expose them to more confusion with N’s=1.
Tell that to people that say HR is too variable even though the athlete is training on a regular schedule, indoors under controlled conditions. I had a coach with over a decade experience, large number of athletes, and in his professional view I wasn’t an outlier. Sure there are times when HR is “off” but those should be exceptions and flags that something is off (stress, fresh, overreaching, dehydrated, etc.).
Sleep, caffeine, change in fitness, heat, altitude.
The only thing I find very reliable is Resting Heart Rate
Unpopular around here, but racing with HR has been more reliable for me than power. I only use power for workouts, but HR and RPE for racing.
I need power in races to control pace due to adrenaline.
I think HR is a pretty good indicator in controlled conditions, but it can be widely variable based on changing conditions and that has to be considered.
yes, its an internal strain that under controlled conditions is showing the response to oxygen demand in muscles (at different power outputs). Seasonal variations is a big one, if its hot outside, then HR will go up because the heart has to work harder for evaporative cooling. Also if you take time off, you’ll either see more responsive HR when fresh, or if you take off enough time, first a higher HR due to quick drop in cardio fitness, and then longer breaks a drop in both cardio and metabolic fitness. Or the opposite of freshness when logging a lot of hours. Things like that have to be considered when looking at HR.
Now if you take those factors into consideration, workout under generally controlled conditions, not stressed out from work/family, getting good sleep, then it should be a lot less variable. Also you know when to look at HR and when to not look at it.
So yes on bad days HR can vary widely, but so can RPE of putting out a 20 minute sweet spot interval or a long upper endurance workout.
Point being, if you have a well established rhythm in your life then during periods where fitness is steady and you are tweaking specific power durations, then HR should not vary widely. On the other hand if you took an offseason, and are in a 3-4 month base training cycle then a decrease in HR is a signal that fitness is improving (go look at people that have posted HR/lactate curves). Or pull up Intervals chart and you can see a shift in HR curve over several seasons where both cardio and metabolic fitness have increased. If you go with the HR is widely variable narrative you are missing out on a valuable tool in my opinion.
I’m sure after you finished your paragraph, the amount of caveats, IF and considerations to keep in mind to make HR useful is larger than the usefulness itself.
My youngest forgets to look at a screw head before pulling out a Philips and stripping it. HR is a tool, learn to use it or ignore it. But please don’t poop on the people that learned to use it and see obvious patterns.
Except the conditions are not controlled. I use HR as a secondary metric (together with power and RPE), but this statement is misleading. A regular schedule does not account for sleep, stress in the athlete‘s personal or work life, etc. Others have given more relevant factors.
HR needs a lot of context for interpretation. E. g. lower heartrate at a given power level might be a sign a increased fitness or fatigue. HR levels have been less useful in my experience. I use HR to pace outdoor endurance rides, because I find that easier than power.
guess I’m a freak of nature 
I have always felt these caveats apply to power as well. Altitude, heat, stress, etc. I would be surprised if a regular user of TR sees much HR variation and if they do they are probably changing intensity.
absolutely
No. Power is power. Whether and how well you can manage a workout depends on the same aforementioned factors. Only altitude is different, because that does reduce the amount of O2 you breathe in, and does shift your power zones downward.
Even the order of workouts can cause a shift of 8-10 bpm: if I tack on an endurance workout after a hard workout, my heart rate is usually in the high 130s or low 140s as opposed to 120–135 bpm range. Should I lower my power targets to hit HR targets? I don’t.
HR has its place in training, but it is a secondary metric.
I was only responding to your claim that this was “controlled”.
That makes HR primary 
Well, for me, HR has that covered. Though RPE always tells me when I am going too hard.
I raced today, never looked at power. Useless race metric for me. I only use it for controlled training. Once the whistle blows, it is 90% RPE, 10% HR, 0% power.
I know it’s unpopular around here, but power is a worthless metric in a race for me when what I can produce will vary on the day, weather, and altitude. On occasion I will see my HR is too low and I know I need to recalibrate my RPE and push harder. But that’s rare.
But, my heart rate on the starting line today was virtually the same as it is now sitting in bed looking at videos.
That sounds like an attempt to make a gotcha argument than to engage in discussion.