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Bug - Low HR target in cycling daily suggested workouts

Inmate #4074922
over 1 year ago

This has been discussed on the Fenix 7 forum starting 2 years ago:

Suggested workout HR for cycling seems low - fēnix 7 Series - Wearables - Garmin Forums

I'm seeing the same thing on my FR265. My suggested workouts are pretty much the same as what JordiGT posted in that thread: Base and Long Ride workouts at 111 bpm target. My Max HR is 187, LTHR 166, RHR 58. 111 bpm would be a brisk walk, I probably couldn't cycle slowly enough to maintain that. There is also a Threshold workout which is reasonable, warmup at 135 bpm and intervals at 165 bpm.

Yesterday I did a workout (not following the DSW) where my average HR was 137 and max 153, and the Training Effect classified it as a base workout.

If I switch to running the Base workouts target 139 bpm, much more reasonable. It's just cycling that has the problem.

  • 0 over 1 year ago

    What happens when you swith to power targets instead of BPM?

    Are you using a chest strap when you bike? How do you get power? What type of power meter do you have?

    You are right 111bpm is 60% of your HR Max, which is at best recovery ride. Indeed 139bpm (75% of HR Max) is a good target for a base ride.

  • 0 over 1 year ago in reply to Etupes25

    Just using the watch for heart rate, but it seems pretty reliable. Indoor smart trainer for power (Tacx Vortex).

    I initially had it on power targets and it was giving me 125W for base, which is actually too much for me. I'd probably be at 160+ bpm. But I'm more forgiving of that because I'm new to cycling, and if I was more experienced it's quite conceivable that 125W would be a good base workout.

    However heart rate mode should be the solution to that issue - no matter my experience level it should be easy to calculate a HR target. And I don't think it's conceivable that 60% MHR would be an appropriate base workout target for anyone. That's why I believe this is purely a bug, and not just "the watch needs to learn more about you."

    Also in case you didn't see in the Fenix 7 thread, the user stuck with the workouts for 4 months and the targets did not improve.

  • 0 over 1 year ago in reply to Inmate #4074922

    There is always the possibility of a bug.

    However, the fact that the watch is giving you a power target for a base workout that is not achievable is a tell-tale sign that the model of HR/power relationship that the watch has built is wrong. FYI, an 125W for a base workout is not outlandish in general, but this number will vary a lot based on your fitness.

    The watch is using your VO2 Max model to select the target.

    A good way to help the watch refine this model is to do the built-in threshold test for cycling (chest strap required). Because it is a calibrated ramp, the test will inform the watch across a variety of efforts and that will improve the ventilation/HR/Power relationship model.

    If you care about the metrics, you need to use a chest strap. No way around it.

  • 0 over 1 year ago in reply to Etupes25

    FR265 doesn't have the FTP test. Just a manual entry (I entered mine as 155W based on a custom ramp workout I made).

  • 0 over 1 year ago in reply to Inmate #4074922

    OK. But it has auto-detection.

    "The Auto Detection feature is turned on by default. The watch can automatically detect your maximum heart rate and lactate threshold during an activity."

    Do you think you can bike 20mn steady at 163W (155W divided by .95 is 163W)? If yes, do it. I should be a maximal effort and the auto-detected LT should be about right.

  • 0 over 1 year ago in reply to Etupes25

    Yes I can try that. But it already detected my LT as 166 from previous workouts, which seems fine.

  • 0 over 1 year ago in reply to Inmate #4074922

    The thing is that auto-detection doesn't work very well if the effort is not steady (for example, if you run high internsity intervals) and/or not a progressive ramp.

    166bpm is 88% of 187bpm. This is not bad at all. The typical 90% found in trained individuals would put your HR Max at 184bpm, so not a big difference. Unfortunately, the HR Max value influences the LTHR detection, so it is a bit of a chicken-and-egg situation. All being said, no big reason to be alarmed by your HR Max accuracy.

    I am still worried that your HR data is biased because you don't use a chest strap.