Classification of physical activity intensities using a wrist-worn accelerometer in 8-12-year-old children

Area of Science:

• Exercise Physiology
• Biomedical Engineering
• Pediatric Health

Background:

• Accurate physical activity intensity assessment relies on population-specific accelerometer cut-points.
• Establishing precise cut-points is crucial for understanding children's activity levels.

Purpose of the Study:

• To determine cut-points for the ActiGraph GT3X+ accelerometer worn on the non-dominant wrist in children aged 8-12 years.
• To compare the classification accuracy of the accelerometer's three axes and vector magnitude (VM) for physical activity intensity.

Main Methods:

• Forty-five children (8-12 years) performed 7 free-living activities wearing wrist-mounted accelerometers.
• Activity intensity was determined using direct observation and heart rate reserve.
• Data from minutes 5-8.5 of each 10-minute activity were analyzed.

Main Results:

• Receiver operating characteristic (ROC) analyses showed area under the curve values for light, moderate, vigorous, and moderate-to-vigorous activity intensities ranging from 0.62 to 0.89.
• Regression analyses yielded prediction equations with R-squared values between 0.70 and 0.77.
• Classification accuracies were comparable across the accelerometer's three axes and VM values.

Conclusions:

• The ActiGraph GT3X+ wrist-worn accelerometer demonstrated comparable activity intensity classification accuracy to previous studies.
• Activity intensities can be reliably determined using axis 1, axis 2, or VM values from this device.
• These findings support the use of wrist-worn accelerometers with established cut-points for pediatric physical activity research.