Accuracy of Heart Rate Measurement by the Fitbit Charge 2 During Wheelchair Activities in People With Spinal Cord Injury: Instrument Validation Study.
Dirk Hoevenaars, Iris E Yocarini, Stylianos Paraschiakos and 4 others
PMID 35044306WHAT IT FOUND
The Fitbit Charge 2 is too inaccurate to trust for heart rate in people with spinal cord injury.
It failed the standard accuracy limit for all activities. Errors were worst in those with high cervical lesions and during strength exercise. Use chest straps instead for clinical decisions.
Key findings
01The Fitbit Charge 2 exceeded the acceptable error limit of 10% for people with spinal cord injury overall, with a mean absolute percentage error of 12.99%.
02Accuracy worsened significantly with higher lesion levels, showing a mean absolute percentage error of 20.43% for those with lesions above T1 compared to 11.16% for those below T5.
03The device underestimated heart rate during strength exercises and wheelchair activities, with agreement dropping as intensity increased.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The Polar H7 chest strap was used as the reference, which is not a gold standard (ECG would be better), though it has high correlation with ECG. The number of valid data points decreased for higher lesion levels because some participants could not perform all activities due to impairment. Blood pressure was not measured, so the link between autonomic dysfunction and device error could not be directly confirmed. The study only tested the Fitbit Charge 2; newer models or different brands may have different accuracy profiles.
Declared interests
The study was approved by the medical ethical committee of Slotervaart Ziekenhuis—Reade. No specific funding sources or conflicts of interest were declared in the provided text beyond the approval.
The easy way to misread this
Do not assume the Fitbit is accurate for people with SCI because it is a popular consumer device. The study shows it fails the standard accuracy threshold for this population, with errors doubling for those with cervical lesions compared to those with lower injuries.