Getting constant Heart Rate intraday data during a day via Web API

[MengL]

Hi,

Our team exported Fitbit Heart Rate intraday data via web API (Link: https://dev.fitbit.com/build/reference/web-api/intraday/get-heartrate-intraday-by-date-range/#Respon... ). However, one of our participants (data was collected in 2017; device: Fitbit Charge HR) has the same HR on 2017-04-28:

{"activities-heart": [{"customHeartRateZones": [], "dateTime": "2017-04-28", "heartRateZones": [{"max": 73, "min": 30, "name": "Out of Range"}, {"max": 102, "min": 73, "name": "Fat Burn"}, {"max": 124, "min": 102, "name": "Cardio"}, {"max": 220, "min": 124, "name": "Peak"}], "value": "72"}], "activities-heart-intraday": {"dataset": [{"time": "00:00:14", "value": 72}, {"time": "00:00:29", "value": 72}, {"time": "00:00:44", "value": 72}, {"time": "00:00:47", "value": 72}, {"time": "00:01:02", "value": 72}, {"time": "00:01:17", "value": 72}, {"time": "00:01:32", "value": 72}, {"time": "00:01:47", "value": 72}, {"time": "00:02:02", "value": 72}, {"time": "00:02:17", "value": 72}, {"time": "00:02:32", "value": 72}, {"time": "00:02:47", "value": 72}, {"time": "00:03:02", "value": 72}, {"time": "00:03:17", "value": 72}, {"time": "00:03:32", "value": 72}, {"time": "00:03:47", "value": 72}, {"time": "00:04:02", "value": 72}, {"time": "00:04:17", "value": 72}, {"time": "00:04:32", "value": 72},...

I also checked the steps intraday data: all minute level's step counts are 0. Since daily total step count is 0, I think that participant did not wear Fitbit on that day.

Does anybody know why we still get HR data and HR=72 on that day? Since this dataset is very old, do you know if we might still get similar issue currently? If so, can we say that days with the same HR (variance=0) should be discarded as it is not reliable and the participant is not wearing Fitbit.

Thanks so much for your help in advance!

Meng

[JohnFitbit]

Hi @MengL,

Was the total step count for this user 0 for the entire day? or just between certain times? The example you provided me indicates that you are referring to a time beginning at 00:00, which tells me the user could have been sleeping during this period. This could explain why you're seeing HR but not steps.

[MengL]

Hi @JohnFitbit ,

Yes, the total step count for this user is 0 on 2017-04-28. I only put the first several rows as an example. All the rows in HR intraday data is 72, and all the rows in steps intraday data is 0.

[JohnFitbit · Accepted solution]

@MengL Thanks for clarifying. It's difficult to tell what occurred here, but my best guess is, because this was a common issue with the Charge HR, the heart rate sensor was possibly picking up a false positive reading for heart rate.

The Charge HR had 3 settings for heart rate (Off, On, and Auto). If the sensor was set to "ON" instead of "Auto", this means that heart rate sensor is looking for heart rate data whether or not it is being worn. "Auto" allows the device to track heart rate if it knows its being worn, and when it's removed, the heart rate sensor is disabled to save battery.

In some situations, the user may not wear the device and leave it on their table overnight, which would explain the 0 steps. Additionally, if the heart rate sensor was set to "ON" while the device was resting on the table, the sensor may have confused the reflection of the table as possible heart rate data, due to how the heart rate sensor determines heart rate. 

Another possible scenario that we've discovered recently is if the wearer of the device is using a pacemaker, which is implanted in the chest to help control irregular heartbeat. This may explain why you are seeing consistent values of 72 bmp for the user, but doesn't explain why they have 0 steps for the day.

I hope this helps.