Project Summary
Accelerometry is standard for objectively measuring physical activity, yet there is surprisingly limited data for
best practices when using accelerometry during early childhood, before the age of 2 years. Hip-based
accelerometry may be uncomfortable for infants and toddlers particularly during periods of sleep, thus reducing
compliance and limiting integrated 24-hour measurements. Wearing the device at the ankle may overcome
such limitations, yet data on the performance of ankle-based accelerometry to classify physical activity
intensity during early childhood is sparse. One study supports the validity of ankle-based accelerometry among
toddlers as young as 14 months, yet the approach has yet to be replicated by an independent research group.
Furthermore, data to calibrate physical activity intensity via accelerometry among mobile yet pre-ambulatory
infants are lacking. Our long-term goal is to develop obesity-prevention interventions targeting physical activity
and sleep during early childhood for families in our rural communities. The goal of this project is to assess the
validity of ankle-based accelerometry in measuring physical activity among 6-24-month-olds, a critical stage to
support developing physical activity behaviors. Our rationale is to provide a valid method to measure children’s
24-hour movement and sleep with one device over a multiple-day assessment with minimal burden on parents
and children. Our specific aims are to 1) Calibrate and validate algorithms to classify physical activity intensity
for pre-ambulatory and ambulatory infants and toddlers (6-24 months old) using ankle- and hip-based
accelerometry and compare the performance between the two wear sites, and 2) Assess the feasibility of the
wear protocol and classification of physical activity intensity for ankle- versus hip-based accelerometry among
6-24-month-olds during a multiple-day assessment in their natural settings. Both aims will use the ActiGraph
GT3X+ accelerometer. In the first aim, children will be encouraged to engage in a series of semi-structured
activities of varying intensities while wearing two accelerometers, one at the ankle and one at the hip. We will
calibrate both devices against direct observation and assess the relative performance of each. In aim 2,
another sample of 6-24-month-olds will be asked to wear an accelerometer at the ankle and hip continuously
over four days in their natural settings, and we will compare parent satisfaction, compliance with the wear
protocol, and estimates of daily physical activity intensity across the two wear sites. This proposed research is
innovative, in our opinion, because it focuses on the possibility of ankle-based accelerometry to measure
physical activity intensity during the early childhood stage and aims to classify physical activity intensity using
accelerometry data for pre-ambulatory infants. This proposed research is significant because it will provide
critical data needed to inform best practices for accelerometry for this age group and may facilitate integrated
measurements of physical activity and sleep over 24-hours via ankle-based accelerometry.
