Different heartrate between mtb and roadbike at the same power output

Hey guys,
I have a concern:

My power output at around 220watts gives me on the mtb a heartrate of 130. Thats normal endurance pace.
But when I do the same amount of power on my roadbike, I have a heartrate of 140-160 beats.
This ramps up, the higher my power outbut becomes. I can definitly not put out the same power on my roadbike.

Another example:
5min power on mtb in a vo2max interval = 420watts
5min power on roadbike = around 70watts less

But why?

Information: I train basically all my intervals on the mtb. Could this be a reason?

I’ll be interested to read what the coaches write as physiology is so interesting.

Back of the napkin math and n=1 experience speaking, I know from the extremes of position between mountain and my TT bike the muscle recruitment is different enough to notice power/HR relationships like you experienced. What exactly is happening physiologically I can not say. I would think either: 1) pathways are not developed in muscle groups used more in a road position and therefore the heart needs to pump more frequently to supply O2; 2) more muscle is being recruited; 3) combination of 1 &2.

Also, lower cadence usually=lower HR for the same power, same position/bike. I’m reversed from you. I experience best power on the TT bike, then road, then mountain. Road being the predominant discipline.


hi there @jannik.wuester - do you happen to have two different powermeters on your bikes? As in two different brands?

Because I see this alot - its not you - its your powermeters reading different, thus causing the confusion. As in your road bike powermeter is reading lower…


Well…so much for me being a coach. :grimacing: :blush: Don’t know about the op but I do use the same pm (Quarq). Maybe it’s in my head…

Hey Frank,
yes I use two different Powermeters but both from the same brand (Quarq).

PM Roadbike: Sram RED AXS Quarq Powermeter (Spider)
PM Mtb: Sram XX1 Quarq Spider

  • both dualsided

Note: Cadence is on average the same on my rides.

Maybe the key point for my ability to put out more power with lower heart rate on my mtb is, that I basically train all my intervals on the mtb. What do you think? Should I change that, to train my muscles that are used on the roadbike?

Do you have a trainer you can hook both bikes up to and compare variance against the trainer’s output?