Zone 2 - power vs. heart rate

Hi! My FTP nowadays is 216. The SYSTM app tells me to stay at 140 Watts for a Zone-2 training, my heart rate at Zone-2 should be within 113 and 139. Only … during that endurance training my heart rate won’t get over 100 BPM.

Unless I adjust the training’s intensity by 10%, then my heart rate rises (near the end of that training session) to barely 113.

I’m pretty sure my 4DP profile is accurate, because it’s recent and I gave everything I got.

So … who’s right? The machine or my gut feeling? And … what’s more reliable for a Zone-2 training? My question is:

  1. Should I use “Power” as my main reference? Or my “Heart Rate”? (which, by the way, is pretty consistent during Endurance-sessions over a greater period of time)

Another thought:
The Full Frontal 4DP test tells me my Zone-5 is all above 160 BPM. The Zone-2 takes 70% of that, which is 112. While normally a Zone-2 is calculated based on someone’s absolute maximum heart rate; mine is 175 (while running). On a bike I won’t reach this, because on a bike the max. heart rate is always lower.

So another question is:
2) Is Zone-5’s lower limit (160, in my case) the right “maximum” value, as a baseline for calculating all the zones? Shouldn’t the absolute maximum heart be used? (175, in my case)

With thanks beforehand!

@geik Yes. It is hard to train by heart rate. It can be all over the place depending on hydration, type of activity, sleep, stress, etc. it also generally lags whereas power is fairly quick to adjust.

@geik I would suggest using your max HR for full frontal for now and you can adjust as needed.


At what heart rate do you get to the first or second ventilatory threshold?

Generally, I pay attention to heart rate in three circumstances:

  1. To make sure a recovery ride stays in HR Zone 1.
  2. After a workout to see how long it takes for my HR to decline to normal - this is a measure of fatigue.
  3. During a workout if my HR stays too long in a higher zone than it should - this is an indication of fatigue. I will not generally stop the workout, but, depending on the circumstances, I might go for a less intense workout in subsequent days.

Hey @geik, your FTP and heart rate zones are very similar to mine. I go by power numbers. HR tells me other stuff, like how recovered I am. I look at it, but dont usually use it for training zones (as per @Heretic post).

It sounds like you have a good endurance base!