Anaerobic zone

lanky_doodle said:

What does Garmin consider anaerobic zone?

It depends on what we talk about.

If you consider training zones, as you probably know already, the "anaerobic" zone  can be a heart rate zone, a power zone or a pace zone. It can be expressed as a % of HR Max, Lactate HR, Reserve HR, Threshold Power or Threshold Pace. You can find online many references on how to set these zones. The point is that this is user defined.

If you consider the training effect and training focus metrics, Garmin is NOT using your training zones and/or how much time you spend in them to determine what is anaerobic. Instead, Garmin estimates how fast and high you build up Excess Post-exercise Oxygen Consumption (EPOC) during your workout, using your HR, HRV, resting HR, your pace or power and your work/rest intervals. The watch evaluates the relationship between your metabolic cost (HR, respiration/HR) and the work you actually produce (pace or power) to evaluate EPOC. The kinetics of EPOC build is taken into account to differentiate aerobic and anaerobic type EPOC. Finally, your typical training patterns are taken into account to derive the training effect from the EPOC.

If you see a mismatch between the intensity of your interval training and the training effect, there could be several reasons:

- your HR Max is off (too high or too low). As a result the watch doesn't calculate the metabolic cost correctly. This is by far the most common issue. Another related consequence of this issue is that your VO2 Max calculation is off.

- your workouts intervals are not hard enough. Anaerobic intervals are hard to sustain for more than 1mn. Any interval you can sustain for 2+mn is probably maximal aerobic at best. Then, you need to repeat at least 6 to 10 of these intervals to get there.

Note that you can set up the aerobic and anaerobic training effect fields on your watch to see how they "build up" during your workout.

I have spent quite a few field HR max test and super hard anaerobic workouts to establish my HR Max more accurately than the typical 220-age formula. Through trial and error, I also have tweaked it up and down by a couple of bpm until a "real" threshold 30mn interval would register as a threshold TE, a "real" anaerobic workout based on % of FTP would be also recognized as anaerobic TE, etc. I am now at a point where the Garmin assessments correspond 100% with the intent of the workouts, the various zone settings, threshold and VO2 Max estimates using various software and platforms.

lanky_doodle said:

I seem to only see anaerobic benefit if it hit Z5 for long periods.

You shouldn't be able hitting Z5 for long periods. Intervals of 3 to 4 mn should be very hard to complete, unless you are an elite athlete. That tells me your HR Max is set too low. If your doctor lets do, do an HR Max field test. They are excruciatingly hard but if you want to optimize your training, it is a good investment (once a year is enough).

lanky_doodle said:

unproductive plus continuing decline in vo2 max.

Well, if your HR Max is off, then everything is off training effect and VO2 estimates. If it is OK, then your training pattern is not good enough to maintain fitness.

lanky_doodle said:

I have traditionally used a strap (yellow HRM-Pro) but recently that seems to have also started to show a decline for some reason so back to just wrist HR,

Don't blame the hardware. Keep using the HRM-Pro. You will get much much better HRV data to evaluate your EPOC.

This response was super helpful.   Thank you!