Interunit and intraunit reliability of the RT3 triaxial accelerometer.

Area of Science:

• Biomedical Engineering
• Kinesiology
• Wearable Technology

Background:

• Quantifying physical activity is increasingly important.
• Triaxial accelerometers are commonly used for this purpose.
• Limited research exists on the reliability of these devices.

Purpose of the Study:

• To assess the interunit and intraunit reliability of RT3 triaxial accelerometers.
• To provide data for accurate physical activity quantification.

Main Methods:

• Twenty-two RT3 units were tested on a laboratory agitator.
• Testing involved movement in two directions and two speeds over three 24-hour periods.
• Shaker variance was documented simultaneously.

Main Results:

• Shaker variance was minimal across all trials (CVs < 0.52%).
• RT3 accelerometers demonstrated good intraunit reliability (CVs < 1.81%).
• Poor interunit reliability was observed, with CVs ranging from 9.5% to 34.7%.

Conclusions:

• For longitudinal studies, consistent use of a single RT3 unit per subject is crucial.
• Cross-sectional studies should avoid using multiple RT3 units due to high between-unit variability.
• Compromised data interpretation can result from using different units across participants.