Cardio fitness score drop

[Aiden_Hockey]

 I have a fitbit Ionic. Ive been wearing it for aabout a month now and I had a Cardio fitness score of 76-81. Today I just checked it and noticed that it drastically dropped all the way to 44. I don't know why or how and was wondering what may have happened.

[Aiden_Hockey]

Now I just checked it again and it now say 78-82. I'm confused

[Twinz]

In one of the screens that explains the score, it uses a US Marathon record holder (Ryan Hall) as an example and cites his score. (81)

What pace do you run at, and at what heart rate? Also, what is your resting heart rate?

When the device shows a range, instead of an actual number, it is sort of "guestimating". When it gives a single number it's more "sure". (Usually tracks some runs with heart rate and GPS-based pace included)

[Aiden_Hockey]

My heart rate is usually around 140-160 bpm when I run, and my resting heart rate varies from 49-53. Also I've seen the Ryan hall vo2 score as well and that's separate from the score it gives me.
Thanks.

Sent from my iPhone

[Aiden_Hockey]

My heart rate is usually around 140-160 bpm when I run, and my resting heart rate varies from 49-53. Also I've seen the Ryan hall vo2 score as well and that's separate from the score it gives me.
Thanks.

[Twinz]

If you are running a 6-minute mile with a 140 heart rate, your score may break into the 80's. But if you are running a 10 minute mile with a 160 heart rate, your score probably shouldn't even be in the 40's. (That's why asked what pace you are running and at what heart rate)

I'm trying to figure out which of the two different scores are most likely to be correct, and go from there.

[Tony.r]

It may be connected to the latest Ap update, I updated my Andriod Ap yesterday afternoon and my score has dropped a couple of points today 😐😐

[Aiden_Hockey]

About 8 minute mile with 150 average heart rate.

Sent from my iPhone

[Twinz]

It sounds like neither of the numbers are correct. Through 2 different Fitbit devices, my score has sat aroud 50. My pace is slower (Usually between 8:45 and 9:00) and my heart rate is higher. (Around 160)

You should be higher than 50 for sure. However, while your pace and heart rate are easily in the "excellent" range, they are not "US marathon record holder" kind of numbers. (Under 5 minute mile, resting heart rate as low as 26bpm) So I would not expect you to get near 80 either. 

Does your GPS/HR data look normal when you run? (No drops without a HR and no loss of GPS signal)

[bbarrera]

Cooper’s test running all out for 12 minutes at a pace of 8 min/mile is VO2max of 43, regardless of age or HR. And 6 min/mile is VO2max of 61. 

[Twinz]

How can the Fitbit calculate how hard your heart is working without HR? Also, the nature of the calculation kind of penalizes you for longer distances. Most anyone's pace is faster if they only have to maintain the pace for a short time. My single-mile pace is a lot faster than my normal 3.5 mile pace. (Never tried a 12 minute run)

[bbarrera]

@Twinz 

I'm suggesting using Cooper test as a reality check on Fitbit's single number estimate. Your score of 50 is approximately running 7 min/mile pace for 12 minutes. Go warm up, and then run as fast as you can for 12 minutes. Plug the distance covered into this calculator:

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

Alternatively, run all out for 1.5 miles and record the time and use this calculator:

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

If you can't run all out at 7 min/mile pace for 12 minutes, then your Fitbit estimate of 50 is probably too high.

Some background. As we know, VO2max ("cardio fitness score") is the maximum amount of oxygen your body uses. It is properly tested in a lab, by measuring oxygen intake and oxygen exhaled. There is no heart rate or estimation, because the test measures the actual amount of oxygen used by your body. Here is an article about how the lab test works:

https://www.dcrainmaker.com/2012/01/look-at-testing-with-new-leaf-fitness.html

There are many ways of estimating VO2max without requiring lab equipment, some of the more well known methods:

- Cooper test developed in 1968, only requires the amount of distance run in 12 minutes (or time required to run 1.5 miles) to estimate VO2max

-  Rockport walking test, involving walking 1 mile and using time, gender, body weight, and heart rate to estimate VO2max

- Firstbeat filed for a patent in 2012, later granted, that uses ratio of output (running pace or cycling power) to input (heart rate) to estimate VO2max. Validated to be 95% accurate.

Fitbit appears to be using a variant of Firstbeat, simplified to not infringe on the patent.

[YesIRan2Day]

I'm 68 yrs old. My fitness score in one week dropped from 55 to 42 to 38.  I know 38 cannot possible be correct.

I currently run the marathon at 8 min pace (3hr 30) and 5k at 6:24 pace (<20min). A full out run for 12 min at 8 pace is a conversational jog! Why did my score drop so suddenly?