Cardio Fitness Score

[adikeenan]

Hi!

My cardio fitness score, up to today, was 45.6, which is very good for women of my age. Today after I went for a 4K run it dropped to 40, which is average. I just find this strange as I exercise nearly every day, varying between 5K-10K runs and weight training in the gym. My resting heart rate generally stays around 48 or 49. I just don't feel that 40 is very accurate but I'd like to know why it happened so suddenly. Thanks!

[bbarrera · Accepted solution]

@adikeenan Start here with Fitbit article on cardio fitness score: 

http://help.fitbit.com/articles/en_US/Help_article/2096/#runs

You sound like a well trained athlete, from everything I've read in sports science I would expect your score to be stable. As VO2max is mostly genetic, I wouldn't expect significant +/- 5 point changes unless you've gone from couch potato to athlete in a 3-6 month period (or lost substantial amount of weight). Also, for well trained athletes increases in score require serious VO2max training and even then some athletes will not see any change in score. These all point to an issue with how the Blaze is estimating your VO2max.

I'm a cyclist and didn't try it on my Blaze, because it requires running. However I have seen reports on Charge 2 forum about the score going down after an easy run. And Fitbit link above states that more accurate scores require running with intensity. Fitbit's estimate wasn't the most accurate in a review that I read at wearable.com (big change in score between review article and VO2max article). Keep in mind this is a new feature, and that data it needs - 10 minute HR and pace on flat ground - is not always the most accurate on Fitbit devices. So if your Blaze is struggling to detect HR or pace accurately, that could also impact your score. 

Try a Cooper's test to estimate your VO2max for comparison:

http://www.exrx.net/Calculators/MinuteRun.html

and for other ways to estimate:

https://en.wikipedia.org/wiki/VO2_max

The last estimation technique in that wikipedia article is Firstbeat. I have used Firstbeat's patented estimation technology on my Garmin bike computer since October, and it took a month of riding for score to settle from initial estimate of 48 down to 42. My score is stable and not impacted by easy rides, to be expected as that is part of the patented estimation process (detecting and throwing out bad data, and only using good data to calculate score).

Hope that helps.

[adikeenan]

Thanks for your help, I'll be sure to check out other ways of measuring it!

[WavyDavey]

If you go on a fast run for 10 minutes, I believe you'd see an increase in the score. The lower intensity of longer runs seems to throw it off.

[bbarrera]

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@WavyDavey wrote:

If you go on a fast run for 10 minutes, I believe you'd see an increase in the score. The lower intensity of longer runs seems to throw it off.

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@WavyDavey Without looking at the data of a long run that decreased a cardio score, my first wild guess is that the longer run had enough cardiac drift (rising HR) to artificially skew the score downward. In other words, Fitbit isn't throwing out bad data, it is using all the data (good and bad) to calculate the wrong score. Just a guess.

[Audi11]

My cardio fitness score dropped 2 categories in one day, as did my sister's. I woke up in the very good (almost excellent) category and after my evening run I dropped to average. Kind of hard to believe my score is average when my resting heart rate is 55. I read the article but it doesn't explain these drastic changes users are seeing. 

[ChchChris]

This happened to me today.   It dropped from 49 to 47.  When i looked at the run details i noticed that the gps had dropped out in the middle of the run so i deleted the run and added it in manually and my score went back to 49.