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Related Experiment Video

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Assessment of Physical Activity Intensity with Accelerometers and Oxygen Consumption

Assessment of Physical Activity Intensity with Accelerometers and Oxygen Consumption

Published on: June 20, 2025

Detection of physical activity types using triaxial accelerometers.

Jørgen Skotte¹, Mette Korshøj, Jesper Kristiansen

¹National Research Centre for the Working Environment, Copenhagen, Denmark.

Journal of Physical Activity & Health

|December 20, 2012

Summary

This study validates a triaxial accelerometer method (Acti4) for accurately identifying various physical activities like walking and running. The system demonstrates high accuracy in distinguishing between sitting, standing, walking, running, cycling, and stair climbing.

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Area of Science:

Biomedical Engineering
Wearable Technology
Human Movement Analysis

Background:

Accurate measurement of physical activity is crucial for health research.
Triaxial accelerometers offer a promising non-invasive method for activity monitoring.
Validation of activity classification algorithms is essential for reliable data.

Purpose of the Study:

To validate a triaxial accelerometer setup for identifying everyday physical activity types.
To assess the accuracy of the Acti4 method in discriminating between sitting, standing, walking, running, cycling, and stair climbing.
To evaluate the performance of thigh-mounted accelerometers for detecting sitting posture during free-living conditions.

Main Methods:

Seventeen subjects wore triaxial accelerometers (ActiGraph GT3X+) at the thigh and hip.
A standardized test protocol included walking, running, cycling, stair climbing, sitting, and standing.
The Acti4 method used standard deviation of acceleration and inclination for activity discrimination.
Thigh accelerometer sitting detection was validated against pressure sensors.

Main Results:

High sensitivity (99%-100%) and specificity (>99%) were achieved for most activities in standardized trials.
Walking stairs detection showed 95% sensitivity.
During 140 hours of free-living data, sitting posture detection achieved 98% sensitivity and 93% specificity.

Conclusions:

The Acti4 method demonstrates high accuracy in classifying multiple physical activities.
The system is effective in both controlled settings and real-world scenarios for activity monitoring.
Triaxial accelerometers provide a reliable tool for objective physical activity assessment.