Endurance rides power vs heart rate

Hello All,

I have a question regarding zone 2 endurance rides. My endurance rides for the most part keep my heart rate in zone 2 but I do experience a drift into zone 3 as time goes on. Should I be reducing the intensity on these zone 2 rides once I see the heart rate going up to zone 3?

Thanks in advance!

No, I wouldn’t worry about it. Unless it impacts you key sessions of the week. Also, there are already plenty of active threads on Z2 where you could find more info.


Here are some quick search results:

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Welcome to the forum! :partying_face:

This is a great question. In addition to what @mcneese.chad found, here are a couple of articles about cardiac drift.

In general, I think the best way to prevent this from happening for as long as possible is to stay hydrated throughout your ride.

In terms of which metric to follow (power vs. HR), metabolically speaking, I think keeping your HR in zone is most impactful, though keeping your power on target might be beneficial for other training purposes.

I’d be curious to hear what @The_Cog has to say about this topic if he hasn’t spoken on it already.


Thank you, much appreciate the help!

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I would throw away the HR monitor, go by perceived exertion, and use the power data for 1) entertainment value during the ride, and 2) post hoc analysis.


There are no hard thresholds across the physiological spectrum.

That said, the zones give us references to train towards.

If your HR drifts up a bit into the next zone, it’s not an issue. That said if it’s much higher than the intended zone, you likely are training too hard. Your FTP could be set too high or you don’t have a reasonable base for the workouts you’re doing.

This is a great reference:

Or, it might be hotter than you are acclimated to, or your plasma volume is reduced due to, e.g., lack of sleep, inadequate CHO intake, etc.

TL,DR: HR is a fickle thing.

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Ain’t too fickle over here :man_shrugging: