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  • Author: Aston K. McCullough x
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Aston K. McCullough and Carol Ewing Garber

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.

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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.

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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.