Another "Zone 5" Thread - Why is this possible?

Since you have HRM pro, please perform lactate threshold run, its approximately 20 minute long and set your HR zones by Lactate threshold and all should be ok.

Zones by LT is what I use and recommend, its most accurate what you can set. After some runs it even suggest me to re-set my zones by newly acquired Max hr or  LT.

JosefK said:

Since you have HRM pro, please perform lactate threshold run, its approximately 20 minute long and set your HR zones by Lactate threshold and all should be ok.

Thanks, and that is on my list to do.  I am eager to see what that does!

But for discussion sake, I was asking a different question.  You're basically saying the watch doesn't know you're a live human being until you do a lactate threshold test...

Note that I've told the watch my age, height, and weight.  Everything else is auto-detected based on my activities.

I'm asking, why would any algorithm ever arrive at such an impossible classification my zone 5?  I can see there being some gray areas for zones 3/4 based on HR, but Zone 5?  You don't even need to know someone's max HR to conclude that such an extended period of time in Zone 5 for a given activity is, by definition, impossible.

Your zones don't take the rest HR into account. Using zones based only on Max HR is OK for general fitness but the worst possible choice for running.

The best choice is using Lactate Threshold based zones. The second best choice is using HR reserve based zones, which takes into account the rest HR. Garmin can do all 3 methods. 

RG said:

I'm asking, why would any algorithm ever arrive at such an impossible classification my zone 5? 

Possibly you did not push yourself hard enough, that the device could have already detected your true max HR. In the same time, the watch cannot simply assume that your max HR is much higher than it detected until now, and shift the zones accordingly, because it could give you false information, and could be potentially harmful for your health and safety.

You can argue, that seeing you've spent 50 minutes in the HRZ 5 without harming yourself, it could assume it is safe to move the zone. No, it could not. If you google the topic, you can see that the opinions differ wildly. OK, you cannot sustain the max HR for much longer than some low tens of seconds, but exercising at 90% (HRZ 5) for an hour is well possible, and apparently not uncommon.

For this reason, it is much better using the LT-based HR Zones, exactly as the previous users recommended. And if you ask why it is not used by default - again because of the safety. Most Garmin users do not necessarily do regular activities intensive enough to get reliable LT or VO₂max values, so the maxHR-based HR Zones are safer and more accurate for them.

Then you can ask why the watch does not automatically switch from max HR to LT based HR Zones once it sees reliable LT data. Well, it certainly could, but then a lot of people would be surprised why their HR Zones suddenly changed. OK, again, it all can be handled with a sufficiently intelligent design, and explanatory messages, but personally I think letting the choice to the user is not a bad idea at all. 

trux - Thanks, and those seem like valid explanations.

trux said:

OK, you cannot sustain the max HR for much longer than some low tens of seconds, but exercising at 90% (HRZ 5) for an hour is well possible, and apparently not uncommon.

You're right, I can sustain an hour at the low end of the current Zone 5, but then by definition it isn't Zone 5.  More like Zone 4.8 (just a guess)?

I could only find this metric in Connect web, but for the above activity, it shows:

Zones:
Avg HR: 5.2 z
Max HR: 5.8 z

% of Max:
Avg HR: 92 % of Max
Max HR: 98 % of Max

If I can work up the nerve, I would like to have a vo2 max test performed at a local athletic lab. The cost seems reasonable.

Hopefully this week I'll get a chance to do the LT test.

I'm 45, with max hr 180, resting hr 45, and threshold 164, almost like you. I can run 1h with average heart rate 166, most of the time in Z5, like you are. But If you want to increase your performance you should not run at these paces every time, unless you want to injure yourself. Oderwise, I think your HR zones are wrong, Z1 should be between 90 to 135, Z2: 135-149, Z3: 150-162, Z4: 163-172 and Z5: 173-183. There are other ways to calculate them but for me this is the best for Garmin watches. Here explains better: 

https://corredordemontana.mundodeportivo.com/actualidad/item/la-intensidad-en-el-trail-running

Google translate and voilà

You should do workouts in all zones, but mostly in Z1-Z2, some in Z3-Z4 and very few in Z5, to progress

yago77 said:

But If you want to increase your performance you should not run at these paces every time, unless you want to injure yourself.

Yes. In fact, the watch recently notified me that I was Unproductive and had a "Low Aerobic Shortage".  I have taken that advice (after doing some research to confirm) and started more weekly activities in Zone 2.  Now I am "Maintaining".

I have definitely ignored the low aerobic area basically for ever.  Except for weightlifting, most all my activities are at the more intense end of the scale: Crossfit, running, tabatas, etc.

In my case, the effect seems be that of hitting a plateau and lack of progress, rather than injury (injury would have happened long ago, and continuously :)

RG said:

You're right, I can sustain an hour at the low end of the current Zone 5, but then by definition it isn't Zone 5.  More like Zone 4.8 (just a guess)?

Yes, as I wrote, an algorithm could be able to detect that the HRZ 5 should be higher, but it would be neither correct nor safe changing it automatically without confirming your Max HR. Either make a true Max HR test, or conduce the Guided LT Test, or even better do the lab test you mentioned. They will give you not only the VO₂max, but also LT and Max HR values.

Actually, for under an hour, zone 5 slightly above your LTHR is where you should be for a max effort. Also, it can only do so much. If you want accurate zones you have to do the tests.