Power discrepancies whilst climbing vs flat road riding vs indoor riding

Hi all,

I have some very specific questions that can possibly be answered very broadly.

I am 192cm tall, 80kg - so my CdA is pretty horrible
FTP 300ish (ramp test) = Z2 power of 166-227W
I enjoy climbing more than flat riding.
I have been following a more polarised approach for the last 1-2 months (removing 1 sweet spot workout per week). Using this approach I recently set a new power PR on a 42 min climb - 290W (this particular climb levels out toward the top so power dropped during this portion).

My problem:
I seem to be able to hold much higher power whilst climbing vs riding on the flat for a given HR. EG - I can easily hold 200-220W at 140BPM at 80-90RPM on an incline, however trying to hold this same wattage/cadence on flat terrain and my HR is 150+ (therefore exceeding my Z2 HR calculated via %HRR)
Additionally, I am able to hold 215W on the indoor trainer well within my Z2 HR values, however when out on flat roads, this same wattage results in a tempo HR.

This has been confirmed on both my trainer bike and road bike. The power meter on the road bike is within a few watts of my Kickr - so all data “should” be accurate

Is it normal to have such variances between climbing and flat road riding?
Is there a physiological reason for any of the above?
Is there a training aspect that can be implemented to improve this?

Thanks in advance!

Is your cadence on the flats equal to the climbs?
Torque * cadence = power

There is apparently a kinetic energy element to the climb vs flat differential point, independent of cadence. Covered in a cyclingtips article many years back. Position and relationship to gravity due to slope can also create a different pedal stroke / muscle recruitment, and the added effort (or discomfort, breathing restriction) when getting aero on the flat can increase HR. Maybe also the added concentration and faster steering adjustments needed when riding that fast on the flat?

Believe indoors vs outdoors may also be a different point and it could also be that you need to use more muscles (eg core, plus small steering adjustments with the upper body) to stay upright outdoors vs a completely static trainer? Not sure if better core coordination could help here?

In addition to the more commonly talked about indoor heat effects which drive HR in the other direction, they are interesting considerations when translating power zones from indoor testing (whatever form) to real world riding

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I was just listening to an old Fast Talk podcast with Colby and Frank Overton. They were talking about equipment and power meters. One point that came up is that with certain power meters, you could get large ring / small ring inconsistency if you didn’t use the right chainrings. The specific example was an SRM that was designed for Dura Ace chainrings and that other chainrings could give spurious results.

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You don’t have a “problem”. What you’re experiencing is typical. Most folks can maintain greater power on climbs than the flats. See Colby Pearce’s recent post for a good explanation:

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Interesting read especially as I’m doing some cadence and torque work at the moment.

Another addition to this I believe I have mentioned somewhere … or dreamt that I have, is to look at doing power testing on flats and hills of the same duration.

You can then look at the descrepancy. As mentioned already most can generate more power on hills than flats, and although this is true, if you can improve generating the power on the flats through pedal stroke, you can get closer and closer. This difference can help you do guide your training in all intensities, and move some to the flats and some on the hills.