StepWatch stride counting: Accuracy,precision,and prediction of energy expenditure in children

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.