"Your heart rate zones are now personalized to your cardiovascular fitness and age." How?

[judetheobscure]

The above message appears on my heart rate page. I've looked at the info link which doesn't say much except its related to a calculated maximum heart rate based on age. But nothing about how the cardiovascular fitness comes in.

So for me, age 56, my max heart rate should be 164. However I regularly reach the 190s and sometimes 200. My resting heart rate is in the mid 50s to low 60s range. And my cardiovascular fitness score is usually 44-48.

My maximum heart rate according to FitBit is 166. Which seems very unhelpful, especially given that that is less than my average when I run. 

I know I can change it. I just think it's not a useful tool at all if it's not actually using things like measured heart rate to make its calculations.

[t.parker]

I don't think Fitbit adjusts zones according to the fitness level. At least I have never noticed such a thing. As far as I am aware, it just uses max HR based only on age. If you are further from the average of the population then your zones won't be correct. A much better way is using lactate threshold for defining HR zones. Fitbit doesn't support LT but it works with TrainingPeaks. If you want to have a more accurate and detailed view of your HR zones (which on Fitbit are rather useless as too simplified) you may sync the Fitbit account with TP. TP will find your lactate threshold and will define your HR zones. You will get a breakdown like below:

TP doesn't care about your max HR but is looking for lactate threshold so your zones are changing with your fitness.

[Heybales]

Not sure what they changed, if anything much actually.

Perhaps they are testing a new formula on a subset of users - and you won!

Ditto's to current system not being that useful if actually training for something.

If just out for exercise, then it might useful to know to stay in low zone for recovery days after a high zone for hard workout day.

Or perhaps just wanting to do a 5k or 10k and know that the middle zone is best for endurance.

(ya, not using zone names since most sites use more)

I can see where Fitbit would not want to take your maxHR seen in a workout and calculate a new HRmax, because what if the maxHR was bogus from an issue and the zones now were way too high and someone attempted to workout to them incorrectly.

But it does seem some notice could be given for people to think about. Like I'm about to say.

With that fitness score which I'd semi-trust as based on good data, if you can hold in the 190's for minutes on end and not really be able to talk in complete sentences (and not be at end of workout dehydrated in 100 F temps), like just going above the aerobic zone - I'd take 190 / 90% and set HRmax manually to 211. For many that might be 85%, but it sounds like you've kept your fitness up through the years.

If you have goals for endurance know to stay in zone, if going for recovery day stay below the zone given, if doing intervals then you want higher.

If you don't have those types of goals - go for whatever feels good.

[shipo]

Unfortunately Fitbit continues to subscribe to the long discredited 220-Age formula to determine maximum heart rate, and while annoying, once folks realize the formula is wrong, steps can be taken to get around it (more on that down below).

In my case, I'm about to turn 64 in a few weeks, I've been an on and off runner most of my life, and when resting have an almost unbelievably slow heart rate (my daily RHR ranges between 41 and 45 these days), and an almost off the chart sleeping heart rate (I think Fitbit bottoms at 30 bpm and I routinely hit 35 while sleeping).  The flip side is also true, when I'm running and in moderate condition, I've seen my heart rate exceed my theoretical max of 156 by several points for over an hour at a time (as my conditioning improves my max sustained drops 20-30 bpm); then there is my initial heart rate when I start each run, regardless of conditioning, I've seen it spike as high as 190 for the first mile, sometimes two, before all of the sudden it drops down to something more reasonable like into the 120-140 range, depending upon my pace.

Back to mitigating the Fitbit estimates; I've adjusted my settings to indicate my Max is 182, and I've also created a "Custom Zone" which ranges from 30-60 bpm, and that nicely disposes of the arbitrary and highly inaccurate "estimates" Fitbit uses for my age.

[judetheobscure]

Some interesting replies. Thank you all.

@t.parker  I've attached a screenshot to show the bit where it says about cardiovascular fitness.

 I shall look up lactate thresholds and Training Peaks.

@Heybales I'm not overly bothered about zones. I don't use them to train. Just look at them in a sad statto type way after whatever exercise I've done! But I do take your point about Fitbit's potential liability if it gives a bogus MHR. 

@shipo I didn't know the heart rate zones were discredited. I'll have a ferret around with Mr Google. 

Out of interest, what is the purpose of the custom 30-60 zone you have set?

[shipo]

@judetheobscure, I set the 30-60 zone simply because I spend 95% of my time there.  Not sure if it was a Fitbit bug back in the day, but before I set that zone, my daily heart rate graph would truncate at something like 40-45 bpm.  When that was happening I could look at my chart for a day and see a flatline for maybe 22 of my 24 hours in a day.

I may try and delete that zone to see if it is still an issue. 

[LZeeW]

@judetheobscure   The concept that 220 - age = MPHR is certifiable junk science.  Here is an interesting read from the NY Times.   You don't need to be a cardiologist or exercise physiologist to understand it.  In research, you don't look at a bunch of data points and draw a line.  There are many reasons why that "research" would never get published today.

[Heybales]

Interesting, I never realized I never looked into the history of it - I figured it was along those lines, like BMI.

Meant for one narrow purpose, others picked it up and ran with it for a much wider and incorrect usage.

Here's a site that gives several formula's - and yet even here - totally wrong for me. Likely because the rate of drop as I age isn't the same since I've kept fit through the years. 14-20 bpm low even using elite option. And my bike and run are equal.

https://www.brianmac.co.uk/maxhr.htm

But I still agree with suggestion above, that if HR zone training is of use for your goals - doing a field test for LT/AT gives most useful info to train to and improve.

@judetheobscure  - what does it say under Learn More - I'm really wondering if you are part of test group and it's not working right.

Anyone else with device that supports fitness scores seeing what is in the screen shot?

I was going to provide some excellent articles on using LT zones for training and their usefulness, but they are behind pay walls now as I guess part of training programs.

[judetheobscure]

Learn more links to this page. 

[Heybales]

Oh good grief, that's it!

Perhaps that means it's just using the HRReserve zone method, which at least tempers the possibly very incorrect HRmax with the measurable restingHR.

But now that calls into question I've seen the RHR not be the traditional before wakeup low of lows, but rather some resting value taken from daytime and night time averages.

Still better than HRmax by itself at least.