Validation of open-source step-counting algorithms for wrist-worn tri-axial accelerometers in cardiovascular patients.

BACKGROUND: Accurate quantification of daily steps in a cardiovascular patient population is of high importance for primary and secondary prevention. While sensor derived step counts have been sufficiently validated for hip-worn devices and commercial wrist-worn devices, there is a lack of knowledge on validity of freely available step counting algorithms for raw acceleration data collected at the wrist. RESEARCH QUESTION: How accurate are step-counting algorithms for wrist worn tri-axial accelerometers in a cardiac rehabilitation training setting? METHODS: Two step counting algorithms (Windowed Peak Detection, Autocorrelation) for tri-axial accelerometers (Axivity AX-3), were tested. Steps were recorded by chest-mounted GoPro video cameras as gold standard. Cardiovascular patients without neurological impairments enrolled in an ambulatory rehabilitation program were recruited. Recordings were performed during one 45-90 min outdoor physical therapy session of which 5-min segments of six movement categories, namely Walking, Running, Nordic, Stairs, Arm Movement [AM] With [+] and Without [-] Walking [W] were identified and analyzed. Mean absolute difference and mean absolute percentage error [MAPE] with regard to true steps measured from video are reported to report accuracy. RESULTS: Training sessions of 22 patients were recorded and analyzed. Steps were overestimated during AM-W and underestimated during Walking, Running and Stairs. Windowed Peak Detection algorithm was more accurate during AM+W and AM-W and Autocorrelation performed better during Nordic. A MAPE of close or below 10% was achieved by both algorithms for the categories: Walking, Running, Stairs and Nordic. SIGNIFICANCE: Both algorithms provided accurate results for estimation of step counts in a controlled setting of a cardiovascular patient population. The quantification of daily number of steps recorded by wrist-worn accelerometers delivering raw data analyzed by freely available algorithms is a cost-effective option for research studies.

Objectively measured adherence to physical activity among patients with coronary artery disease: Comparison of the 2010 and 2020 World Health Organization guidelines and daily steps.

Background: Tailored recommendations for patients after percutaneous coronary interventions (PCI) need physical activity (PA) to be objectively measured and assessed for adherence to guidelines. The recent WHO guidelines removed the daily recommended bout duration, while the potential impact of this change on patients after PCI remains unclear. Aim: We evaluated prevalence estimates of adherence to PA recommendations among patients after PCI across the 2010 [≥30 min moderate- to vigorous-intensity PA (MVPA) at ≥ 10-min bout duration] and 2020 WHO guidelines (≥30 min of MVPA of any bout duration), as well as 7,500 and 10,000 steps. Methods: We conducted an observational longitudinal single-center study with patients after PCI for chronic or acute coronary syndrome (ACS); maximal age 80 years. Wrist-worn accelerometers recorded participants' PA data from the evening of hospital discharge over the next 18 days. Results: We analyzed data from 282 participants with sufficient minimum wear time (7 days of ≥12 h), including 45 (16%) women; and 249 (88%) with ACS. Median wear time was 18 (17, 18) days. Median participant age was 62 (55, 69) years. Fifty-two participants (18.4%) fulfilled 2010 WHO guidelines and 226 (80.1%) fulfilled the 2020 WHO guidelines. Further, 209 (74.1%) participants achieved ≥7,500 steps/day and 155 (55.0%) performed ≥10,000 steps/day. Conclusion: Among participants after PCI, most MVPA was accumulated in bouts <10 min, leading to a fourfold discrepancy between participants fulfilling the 2010 and 2020 WHO PA recommendations. The number of steps/day may be a valid proxy to recent WHO PA recommendations as it is not dependent on the bout-length definition. Clinical trial registration: [ClinicalTrials.gov], identifier [NCT04663373].