Inter-Instrument Reliability and Agreement of Fitbit Charge Measurements of Heart Rate and Activity at Rest, during the Modified Canadian Aerobic Fitness Test, and in Recovery
Bibliographic record
Abstract
Purpose: We determined the inter-instrument reliability and agreement parameters of the Fitbit Charge Heart Rate (Charge HR) device during three phases: rest, modified Canadian Aerobic Fitness Test (mCAFT), and recovery. Method: We recruited 60 participants for this cross-sectional measurement study using convenience and snowball sampling approaches. The performance of the Charge HR was assessed throughout the rest, mCAFT, and recovery phases. To establish inter-instrument reliability, the Charge HR variables – heart rate, steps taken, and energy expenditures – were compared with those for two other devices: the Zephyr BioHarness (ZB) for heart rate and the Fitbit One for steps taken and energy expenditure. Measurements were recorded every 30 seconds. Results: At rest, the inter-instrument intra-class correlation coefficient (ICC) (standard error of measurement [SEM]) for the Charge HR versus the ZB was ≥ 0.97 (range, min–max, 1.02–1.32). During the mCAFT and in recovery, the ICCs (SEMs) for the Charge HR and the ZB were ≥ 0.89 (range, min–max, 1.30–3.98) and ≥ 0.68 (range, min–max, 3.58–8.35), respectively. During the mCAFT only, the number of steps taken and the energy expenditure recorded by the Charge HR and the Fitbit One displayed ICCs (SEMs) of 0.97 (83.00) and 0.77 (14.70), respectively. The average agreement differences in heart rate in this pair-wise device comparison indicated mean differences of –0.20, 4.00, and 1.00 beats per minute at rest, during the mCAFT, and in recovery, respectively. Conclusions: The Charge HR heart rate variable demonstrated excellent inter-instrument reliability compared with the ZB and provided good levels of agreement. The steps taken and energy expenditure variables displayed excellent reliability measures between Charge HR and Fitbit One. Our findings may be used to capture field-based wireless measures of heart rate in various phases and provide information about possibly using the Charge HR and ZB devices interchangeably.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.007 | 0.016 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".