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Updated: May 22, 2026
Assessing the Accuracy of Fitness Smartwatch Data for Cardiovascular and Physical Activity Monitoring: A Validation Study in Digital Health
Published on: February 21, 2025
StepWatch stride counting: accuracy, precision, and prediction of energy expenditure in children
Kristie F Bjornson1, Delphine Yung, Kevin Jacques
1Developmental Medicine, Seattle Children's Research Institute, University of Washington, Seattle, WA, USA. kristie.bjornson@seattlechildrens.org
Introduction:
Accuracy and precision of the StepWatch (SW) was tested in typically developing youth (TDY) with the prediction of oxygen consumption derived from stride counts.
Methods:
Ten TDY (5 boys, 5 girls) with an average age 14.1 years (SD=2.2) enrolled. Participants underwent treadmill cardiopulmonary exercise testing (CPET) wearing two SW devices at 1, 2, 3, and 4 miles per hour (mph).
Results:
Average sign-corrected disagreement for strides counted between the 2 monitors was 0.4 (0.52), 0.2 (0.42), 0.1 (0.32), and 0.1 (0.32) for 1, 2, 3, and 4 mph, respectively. The ratio of SW counts to observed manual counts averaged 100.03% with ICC=0.995. Oxygen consumption equations were derived from resting and walking VO(2), age, gender, and stride counts.
Conclusions:
Excellent accuracy and precision was documented for treadmill walking speeds up to 4 mph while VO(2) per number of strides taken appears to decrease with age and is lower in girls.
