I’m little confused by the HR and Power diagrams for a workout.
Today I made an outdoor 1:44 hour long endurance workout (I thought).
And my HR-diagram also shows this:
But my power-diagram is more varied:
For example it shows I was in tempo abt 27 min and sweet spot abt 16 min.
I understand this depends on the terrain, wind and how hard I work. But if my average HR and power is in the Z2 zone, is this an endurance workout or not?
Some things to consider:
HR zones might be wrong
Power zones might be wrong
Your LTHR might be wrong
I use to perform 4/5 x 5m @ “VO2 power zone” in order to calibrate my HR zone. Always as an average due to the hr variance from one day to another.
Other factor to consider is the time on which you calculate you em effort. If it is at the beginning or at the end of a 3 hours ride due to decoupling factor.
Sailer is still to determine how and why this decoupling happens.
Most important is you adopt one (hr ou power) and compare your improvements with yourself
Nearly all workouts are endurance workouts.
That’s probably the most simple sentence so that you don’t worry too much. The next question is what what the purpose of the workout. If it was to accumulate time in Z1/2, and feel fresh for the next workout, then you have probably pushed a bit hard and used a bit more of your glycolytic system than is ideal, which you could give you a bit more fatigue for no real additional adaptation. But then another question is, when is your next workout?
It’s also a pretty short session for a true LSR for aerobic adaptation, but then that depends on your existing fitness.
Remember also, that power is an input, heartrate is a response. So it is possible to keep your heart rate low but have lots of time at higher power, if those efforts are short and do not significantly raise your heart rate.
Lots of questions to build context basically! If I was your coach and had prescribed a long slow aerobic ride, I would suggest that you try to cap your power (so don’t surge on hills, for examples) and then stretch the duration out.
Thanks for the answer.
The purpose of this workout was easy endurance, but it was ridden in a slightly hilly terrain where I pushed harder on the uphills.
My weekly schedule is 3 rides a week. With 2 shorter ones (1-1.5 hr) with tempo and SS. The third ride is endurance, where I try increase the ride time every week. And I also take a recover week every 3-4 week. My long term goal this season, is fitness and also a longer event in September (200 km).
Great! On the endurance ones, try to keep the whole thing Z2 power or close to Z2 power - don’t surge on the hills. This should allow you to go longer, and make you a little fresher for your focused workouts.
Nothing above threshold?
If your goal was to do just a straight easy endurance workout then this is something you’ll have to practice not doing and be a little self-disciplined with. If even power is your goal then you will probably find that you are going annoyingly slow on the uphills and will be shifting way more than you are used to.
The other thing is to keep the power down on the descents and to make sure you are pedaling the entire time. As much as you want to limit your time above tempo you also want to limit the time spend below endurance. You spend almost 25% of the ride below 55% FTP. Try to aim to make that 10% or lower. Here’s and example from a recent century ride (I had some sections at low tempo so that’s why that zone has a bunch of time"
But over 5ish hours I spend less than 20 min coasting or easy pedaling.
During my endurance rides I do sometimes a couple all-out sprint 30 sec long. But nothing else in Z5 zone.
Thanks for all information.
Things start to become more complicated now when I have a power sensor. Before this it was easier training with only HR zones.
Ah yes be careful what you wish for and all that 
My number one piece of advice, is before every session ask yourself ‘Why am I doing this? What is the purpose of this session’?
If you understand the purpose, it will help a lot not to mix up energy systems randomly. For example:
‘This session I am aiming to improve my LTP (aerobic capacity) and fatigue resistence. So I am going to go further than normal (say 4 hours), spend as much time in Z2 as possible, and not let my power go in to zone 3 where possible.’
Or:
‘This session I am aiming to improve my VO2 max, so I will do 3 minute repeats at 120% of FTP, with very easy spinning in between’
Or:
I am going out for a ride with friends, and it is very hilly and they always surge on hills. I will make the most of the ride by minimizing effort on the flats, and ensure on the hills I am going above threshold to improve VO2 max and repeatability. I will use the sections in between to recover’
Brilliant advice. Giving meaning to every training session avoids a lot of “junk miles” and discipline will keep you from getting exhausted/overtrained.
Marku, are you 75 years old ?
If not there is something wrong with your HR-zones. They look way to low. MaxHR =145?
No problem with my HR-zones.
I’m 67 but my max HR have always been low. Which shows the HR-age formula is worthless.
Now when I’m in this age, I don’t want to do any max-HR test, but when I was 50 I did it and then my max was 150. (And the age-formula said it should have been 170!).
I confess the 145 I have set, is only an estimated number, but I’m sure my max-HR has not got higher then 17 years ago.
That is 100% correct. Never trust that formula.
But you could be better off calculating your HR Training zones following Karvonen. Based on HRR (Heart Rate Reserve = MaxHR - RestHR). The zones will be more condensed this way and that might improve the zone discrepancy with power drastically.
Edit: forgot to add a calculator:
https://www.calculatorsoup.com/calculators/health/target-heart-rate-zone-calculator.php
Thanks for info.
I calculated by using MHR and RHR. Which raised my current Z2 zone with about 10 bpm.
The zones I use now are from Andy Coggan’s 5 zones, with RestHR=45, LTR=123, MaxHR=145. The LTR is from a 20 minute test outdoors, but several months ago. Maybe I’m going to redo the test, but I felt it was very exhausting, and not fun to do.
Well, there are not a lot of tests that are “fun” 
LTHR might change quite a bit when starting with endurance training but once you’ve been training consistently for about 2 years it won’t cange much anymore. For the Karvonen model, you don’t need LTHR. But a correct HRmax and HRrest are needed. Don’t use the formula or defaults.
You have a power meter, so it’s better to use power as the primary metric for harder efforts. Use HR during longer steady state riding. If you have a good idea where your LT1 is, its easier to just use HR in my opinion.
Thanks for the info.
I did a 20 min outdoor FTP-test today. My LTHR was same as a half year ago, but my FTP has increased with 15w. Nice to see this improvement, but I don’t chase a higher FTP-number. Good if my training raise it, but not so important.
Been following this thread as I’m new to power too and am experiencing a similar situation… My endurance rides based on HR were all Z1/Z2 until I added power and ICU suddently determined I was playing with Z3 and Z4 power on hills and getting up to speed after stops while my HR stayed firmly Z1/Z2.
Historically, Strava and ICU fitness graphs mostly aligned, but now there is a huge divergence where Strava (based on HR) shows continued loss in fitness during endurance rides (with a very low HR) and fatigue where ICU (based on power) shows stead increase in fitness.
I live in a city so am constantly starting and stopping during my long rides. One question - are you really in Zone 3/4 when you are out of the saddle starting from a stop? Seems impossible not to go into Z3 getting up to speed and it doesn’t feel like work at all with seemingly different muscles in play. Certainly doesn’t tax my HR.
That’s the big difference between HR and Power. Power numbers are output and they react immediately. HR always lags and short intensity bursts are not detected. Any acceleration shorter then 30sec can be pretty intense and will still go almost unnoticed in HR chart.
Yes, you really are in the higher zones when starting/accelerating. Long endurance rides can’t be done “as supposed” in the city. That is more like a fartlek workout and taxes you system more then intended.
Anecdotally, your answer checks out… my supposed long base rides on Monday/Tuesday left me embarrassingly flat for a hard group ride yesterday when I kept on getting dropped where normally I am more of a hammer. My legs kept giving out before I could get into Z4 HR.