Fitbit Air Just Got BETTER!

Name: Fitbit Air Just Got BETTER!
Uploaded: 2026-06-06T15:15:46.000Z
Duration: 21 min 19 s
Channel: The Quantified Scientist

The Quantified ScientistJune 6, 202621m

Topics13

Introduction to Biceps vs Wrist Testing for Fitbit Air0:00 Heart Rate and HRV Tracking During Illness Night1:00 Biceps vs Wrist Comparison - Heart Rate2:31 Heart Rate Variability Data Issues4:00 Sleep Stage Tracking Comparison5:30 Sleep Stage Agreement Percentages7:02 Workout Testing Plan8:01 Indoor Cycling Results11:10 Running Results12:32 Weightlifting Results13:33 Percentile Rankings vs Competition15:02 Sleep Stage Validation Against EEG Reference16:00 Comparison to Whoop and App Considerations18:32

In a Nutshell

The Fitbit Air performs similarly on the wrist and biceps for nighttime heart rate, HRV, and sleep stage tracking, with both placements showing strong agreement to references. During exercise, however, the biceps placement delivers substantially better heart rate accuracy—especially in weightlifting—achieving 87-95th percentile rankings versus 55-74th for the wrist. This makes the device a competitive Whoop alternative when paired with a biceps band, which third-party options will soon support.

AI-Generated Notes

These notes were generated by AI and may contain inaccuracies.

Most wearables get a much cleaner signal on the biceps than they do on the wrist. The goal is to do a first analysis to see if there's any indication that the Fitbit Air performs better on the biceps. The test compares the Fitbit Air on the wrist to the Fitbit Air on the biceps, measuring heart rate and heart rate variability during the night. This is an initial test, with a more in-depth analysis planned in a few weeks.

A custom biceps band was created for the Fitbit Air. There is concern that wearing it on the biceps might decrease performance for some features like sleep stage tracking, since the algorithm might be perfectly tuned to tracking on the wrist and not function well on the biceps.

During a night when sickness occurred, resting heart rate increased significantly and heart rate variability dropped drastically after 1.5 to 2 hours, coinciding with when symptoms began. The Fitbit Air on the wrist was compared to an ECG chest strap reference device. The reference is shown in red and the Fitbit Air in blue-green, showing almost perfect agreement with only a small, minor deviation.

This provides a first indication that the Fitbit Air can track drastic changes in heart rate and heart rate variability. The reference showed heart rate varying between approximately 47 BPM and 41 BPM, a 6 BPM difference, and the Fitbit Air showed somewhat similar patterns even in this narrow range.

For the same night measured with the device on the biceps, similar quality agreement was observed compared to the reference. One is not clearly better than the other; both are roughly in the same quality range. A second night showed the same result: good agreement on the wrist with some small deviations in a narrow heart rate range, and the same quality on the biceps.

Heart rate and heart rate variability calculations were tested using different averaging windows (average of a minute, five minutes, or 30 seconds) to find the best match with what the Fitbit Air exports, since it is not clear how Fitbit calculates these values. Examples include averaging over 900 seconds versus 600 seconds.

For heart rate variability on the wrist, Elite HRV showed slightly higher values than the Fitbit Air, but overall general patterns matched over the night. When worn on the biceps, Fitbit did not provide all the data—only the first 2 hours of the night could be exported. It is unclear why HRV data was missing, possibly due to signal quality being deemed insufficient.

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Fitbit Air Just Got BETTER!

Introduction to Biceps vs Wrist Testing for Fitbit Air00:00

Heart Rate and HRV Tracking During Illness Night01:00

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