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The Performance of Ankle- and Waist-Based Accelerometry in Quantifying Physical Activity Intensity Among 6- to
Hannah J Dorris1, Delaina D Carlson2, Grace A Ballarino2
1Quantitative Biomedical Sciences Graduate Program, Geisel School of Medicine at Dartmouth College, Lebanon, New Hampshire, USA.
Insights
Accelerometers on ankles can accurately measure physical activity (PA) intensity in infants and toddlers. This objective measurement helps classify sedentary and non-sedentary behaviors in young children.
Area of Science:
- Pediatric physical activity measurement
- Biomedical engineering
- Child development research
Background:
- Objective measurement of physical activity (PA) intensity in infants and toddlers is challenging.
- Existing methods often lack accuracy for this age group.
- Accelerometry shows promise for objective PA assessment.
Purpose of the Study:
- To quantify the performance of accelerometry in objectively measuring physical activity (PA) intensity.
- To evaluate accelerometry placement (ankle vs. waist) for PA assessment in young children.
- To establish thresholds for classifying PA intensity using accelerometry data.
Main Methods:
- Thirty-eight infants and toddlers (6-24 months) participated in a lab visit.
- Accelerometers were worn on each ankle and the waist during various activities.
- Video recordings were used to code PA intensity (5-level scale) for 5-second epochs.
- Logistic regression models identified vector magnitude thresholds for PA classification.
Main Results:
- Ankle-worn accelerometers showed adequate validity for classifying non-sedentary behaviors (≥77.6% agreement, kappa ≥0.44).
- Left ankle placement demonstrated superior performance compared to waist placement.
- Classification accuracy was poor when distinguishing all five PA intensity levels concurrently.
Conclusions:
- Ankle-worn accelerometry is valid for classifying in-the-moment and total non-sedentary behaviors in infants and toddlers.
- Findings offer insights into objective PA measurement for this age group.
- Further research is needed to validate these findings in naturalistic settings.
Objectives:
We aim to quantify the performance of accelerometry in objectively measuring physical activity (PA) intensity among infants and toddlers.
Methods:
Thirty-eight 6- to 24-month-olds participated in a 30-min, semistructured lab visit. Twenty-three (61%) children could walk independently. Children engaged in a variety of activities while wearing accelerometers on each ankle and at the waist. Visits were video recorded, and study team members independently coded the first three 5-s epochs of each minute for PA intensity using a 5-level scale ranging from 1 = completely sedentary to 5 = moderate-to-high intensity. Interrater agreement for PA classifications was excellent (median kappa per child = 0.85). A series of logistic regression models were fit to find the vector magnitude threshold per 5-s epoch that differentiated activity intensity above each PA level with ≥ 80% sensitivity.
Results:
Analyses included 3191 epochs; a median of 88 epochs per child. The classification performance applying all thresholds concurrently for the five PA intensity levels was poor for each wear location (agreement < 50%, kappa < 0.25). Classification improved when concatenating intensity levels, with the best performance comparing sedentary (levels 1-2) to nonsedentary (levels 3-5) and using data from the left ankle device: agreement ≥ 77.6%, kappa ≥ 0.44. Applying those novel thresholds to predict the total time spent in level 3-5 activities over all coded epochs using linear regression performed as well as using the sum of vector magnitude across epochs when using data from the left ankle device. Overall, the performance of the left ankle wear location was similar to the right ankle wear location and superior to the waist location.
Conclusions:
Ankle-worn accelerometry had adequate validity to classify in-the-moment nonsedentary behaviours and total time spent nonsedentary over a time interval among this sample of infants and toddlers. While caution is warranted when generalizing these lab-based findings to naturalistic settings, findings provide insight into objective measures of PA for this age range.
