The accuracy of the TriTrac-R3D accelerometer to estimate energy expenditure. Med. Sci. Sports Exerc., Vol. 31, No. 5, pp. 747-754, 1999.
Purpose: This study examined the reliability and validity of the TriTrac-R3D triaxial accelerometer to estimate energy expenditure during various modes of exercise.
Methods: Twenty subjects (age = 21.5 ± 3.4 yr; body mass index = 23.3 ± 3.6 kg·m−2) performed five exercises (treadmill walking, treadmill running, stepping, stationary cycling, and slideboard), with each lasting 20-30 min and workload increased at 10-min intervals. To test the inter-TriTrac reliability, two TriTrac-R3D accelerometers were worn during each exercise period, and to examine validity, a simultaneous measurement of energy expenditure was made using indirect calorimetry (SensorMedics 2900 Metabolic Cart).
Results: Results showed a significant correlation between the two TriTrac-R3D accelerometers during all exercises. The difference in estimated energy expenditure between the two accelerometers during the walking, stepping, and slideboard exercises was less than 1 kcal·min−1 but statistically significant (P < 0.05). There was also a significant correlation between energy expenditure estimated by each of the TriTrac-R3D accelerometers and indirect calorimetry during walking, running, stepping, and slideboard exercise (P < 0.05). The interaction of Method × Workload was significant (P < 0.05) for each exercise, indicating that the TriTrac-R3D underestimates energy expenditure and that the magnitude of this underestimation increases as workload increases.
Conclusions: Therefore, energy expenditure estimated via triaxial accelerometry does not increase with increasing workloads. These results suggest that there are limitations to using triaxial accelerometry to quantify energy expenditure.