The Performance of Ankle- and Waist-Based Accelerometry in Quantifying Physical Activity Intensity Among 6- to...

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.