The Performance of Ankle- and Waist-Based Accelerometry in Quantifying Physical Activity Intensity Among 6- to 24-Month-Year-Olds: A Semistructured Laboratory Study.

The analysis included 38 children, and only 15 were nonambulatory, so findings for children who cannot walk independently are less stable. The study had only 77 epochs in levels 4 to 5 for nonambulatory children. The visit was a 30-minute laboratory session with encouraged play, not a full day at home or in the community. Epochs were excluded when the child was picked up by an adult or was playing with the devices, but in practice those movements are common and the accelerometer cannot separate them from the child's own movement. The waist device was worn near the hip with an elastic belt, not directly above the right hip as in some prior studies, so results may not apply to a different hip placement. The ankle classification was acceptable but not high, and there was considerable child-to-child variability within activity levels. The study did not test wrist-worn devices.

The authors declare no conflicts of interest. The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases, and the funder had no role in study design, analysis, writing, or publication.

Do not conclude that ankle accelerometry can accurately identify moderate-to-vigorous activity in an individual infant. The five-level classifier performed poorly, with agreement under 50% and kappa 0.25 or less, and only a sedentary-or-not classification reached acceptable agreement.