The purpose of this study was to test the validity and reliability of a brief, wearable, sensor-based screening tool for risk of insufficient daily physical activity (PA) in toddlers. Families (N = 119) with 24- to 35-month-old children attending an Early Head Start (EHS) in a major metropolitan area were recruited. Children wore accelerometers for 7 days, including the usual ∼3.5 hours/week during which children attended the EHS. After applying wear time criteria, accelerometer data from 50 children were included in further analyses. For each child, 15-minute samples of raw triaxial accelerometer data were randomly extracted from the period of time during which children were in the EHS. Using a custom scoring tool, PHIT (Physical Inactivity Test), accelerometer signals were scored for the presence of total PA (TPA) and moderate-to-vigorous PA (MVPA). TPA and MVPA PHIT scores derived from 15-minute samples were respectively used to classify children meeting TPA and MVPA recommendations as determined during the 7-day period. Cross-validated misclassification errors were used to evaluate PHIT score performance. The Spearman-Brown Prophecy formula was used to determine the number of 15-minute samples needed to achieve sufficient reliability (r ≥ 0.70). Using one 15-minute sample, misclassification errors for TPA and MVPA PHIT scores were 19% and 13%, respectively. Spearman-Brown analyses showed that three samples yielded TPA and MVPA PHIT score reliabilities of r = 0.79 and r = 0.75, respectively. Using three samples, PHIT score misclassification errors for identifying insufficient TPA and MVPA in toddlers were 28% and 20%, respectively. PHIT was a valid and reliable tool for PA surveillance in toddlers.
Aston K. McCullough and Carol Ewing Garber
Christopher C. Moore, Aston K. McCullough, Elroy J. Aguiar, Scott W. Ducharme and Catrine Tudor-Locke
Background: The authors conducted a scoping review as a first step toward establishing harmonized (ie, consistent and compatible), empirically based best practices for validating step-counting wearable technologies. Purpose: To catalog studies validating step-counting wearable technologies during treadmill ambulation. Methods: The authors searched PubMed and SPORTDiscus in August 2019 to identify treadmill-based validation studies that employed the criterion of directly observed (including video recorded) steps and cataloged study sample characteristics, protocol details, and analytical procedures. Where reported, speed- and wear location–specific mean absolute percentage error (MAPE) values were tabulated. Weighted median MAPE values were calculated by wear location and a 0.2-m/s speed increment. Results: Seventy-seven eligible studies were identified: most had samples averaging 54% (SD = 5%) female and 27 (5) years of age, treadmill protocols consisting of 3 to 5 bouts at speeds of 0.8 (0.1) to 1.6 (0.2) m/s, and reported measures of bias. Eleven studies provided MAPE values at treadmill speeds of 1.1 to 1.8 m/s; their weighted median MAPE values were 7% to 11% for wrist-worn, 1% to 4% for waist-worn, and ≤1% for thigh-worn devices. Conclusions: Despite divergent study methodologies, the authors identified common practices and summarized MAPE values representing device step-count accuracy during treadmill walking. These initial empirical findings should be further refined to ultimately establish harmonized best practices for validating wearable technologies.
Elroy J. Aguiar, Zachary R. Gould, Scott W. Ducharme, Chris C. Moore, Aston K. McCullough and Catrine Tudor-Locke
Background: A walking cadence of ≥100 steps/min corresponds to minimally moderate intensity, absolutely defined as ≥3 metabolic equivalents (METs). This threshold has primarily been calibrated during treadmill walking. There is a need to determine the classification accuracy of this cadence threshold to predict intensity during overground walking. Methods: In this laboratory-based cross-sectional investigation, participants (N = 75, 49.3% women, age 21–40 y) performed a single 5-minute overground (hallway) walking trial at a self-selected preferred pace. Steps accumulated during each trial were hand tallied and converted to cadence (steps/min). Oxygen uptake was measured using indirect calorimetry and converted to METs. The classification accuracy (sensitivity, specificity, overall accuracy, and positive predictive value) of ≥100 steps/min to predict ≥3 METs was calculated. Results: A cadence threshold of ≥100 steps/min yielded an overall accuracy (combined sensitivity and specificity) of 73.3% for predicting minimally moderate intensity. Moreover, for individuals walking at a cadence ≥100 steps/min, the probability (positive predictive value) of achieving minimally moderate intensity was 80.3%. Conclusions: Although primarily developed using treadmill-based protocols, a cadence threshold of ≥100 steps/min for young adults appears to be a valid heuristic value (evidence-based, rounded, practical) associated with minimally moderate intensity during overground walking performed at a self-selected preferred pace.