After the update to 19.20 my fitness age went from 46 to 55. vo2 max the same at 43

The thing is before the change which was based solely on VO2Max seemingly every 50+ year old Garmin user was told they had a fitness age of 20 and were in the top 1% - that always seemed unrealistic and unlikely.

I suspect the new way of measuring is more accurate or at less less prone to exagerration. As a 50+ something the new metric is less flattering but probably more in the ballpark.

That might be the case but my wife, who is 57 and far less fit than me has a vo2 max of only 32 and a fitness age of 53, which is kinda ok (she does train to get her wight down) but her numbers stayed unchanged after the update. Also all here fitness age data points from the last year are still there (she has a Venu).

So, did Garmin suddenly decide to remove years of historical data to start with a clean sheet after they maybe, unconfirmed, decided to change their calculation method?

BTW, I was always in the top 25% for my age and gender, never saw age 20 and 1%, as you said.

I'm 45yo, VO2MAX 51 and before 19.20 my fitness age was 20 and I was in the top 10%.

Not very realistic...

Since yesterday my fitness age (now based on VO2MAX, BMI and HR at rest) is 36.5years. It says that with 3day/week of high intensity activity I will gain another 0.5 year.

I'm still in top 10% for may age and sex

Same here, but I find the new system seems to get a better estimate of the fitness age. I'm 38 and my Fitness Age went from 20 to 30 years, althouth I could improve -0.5 if I add more HIIT intervals. Seems reasonable to me.

Not so. Being based solely on VO2max meant a direct comparison could legitimately be made between your VO2max and the average of people of different ages. A 50+ year old would have needed a VO2max somewhere in the 50s to have a fitness age of 20.

Now, at 66 yrs, my max attainable apparently is 55.5, which I'm currently at. Pushing my VO2max from 46 into the 50s, even if possible, wouldn't change my new fitness age, even though I would clearly be aerobically fitter than most people half my age, because VO2max is apparently no longer part of the calculation, based as it is on vigorous activity over the past four weeks, BMI and RHR.

They should have kept the old one as a fitness age and labeled the new one something like physiological age.

It told my I would also gain another half year. I've now got that 3 day/wk high intensity but it didn't give me my reward. lol!

BTW, a VO2max of 51 probably puts you in line aerobically with the average 20 year old, and into the top 10 percent of your age group. Quite realistic.

Lol. Not the case.  I'm 6ft, 190. More weight training than cardio and vo2 is at 41. I've been running for a year.  

No flattering numbers popping up in my watch.

Good to introduce a better way to calculate fitness age. Bad that you cannot enter body fat% manually if you don't have a Garmin scales. I hate this kind of exclusion,.