Estimating energy expenditure with the RT3 triaxial accelerometer

Area of Science:

• Exercise Physiology
• Human Metabolism
• Biomedical Engineering

Background:

• The RT3 triaxial accelerometer is a newer device intended to replace the TniTrac for activity monitoring.
• Validating new wearable technology against established methods is crucial for accurate physiological measurements.

Purpose of the Study:

• To validate the RT3 triaxial accelerometer against doubly labeled water (DLW) for measuring energy expenditure in free-living adults.
• To assess the accuracy of the RT3 in estimating total energy expenditure (TEE) and activity-related energy expenditure (AEE).

Main Methods:

• Thirty-six adults (18-56 years) participated in a 15-day study.
• Total energy expenditure (TEE) was measured using doubly labeled water (DLW) as the criterion method.
• The RT3 accelerometer was worn for 14 consecutive days to estimate TEE and AEE using its proprietary equation.

Main Results:

• The RT3 underestimated TEE by an average of 539 kJ (4%) compared to DLW.
• The RT3 underestimated AEE by an average of 485 kJ (15%) compared to DLW.
• RT3 measurements showed reasonable accuracy at the group level for AEE.

Conclusions:

• The RT3 triaxial accelerometer provides a relatively accurate group-level assessment of free-living activity-related energy expenditure.
• The device generally underestimates both total and activity-related energy expenditure when compared to DLW in adults.