Physical Activity‐Related Energy Expenditure With the RT3 and TriTrac Accelerometers in Overweight Adults

Abstract

The objective was to evaluate two accelerometers, the RT3 and the TriTrac-R3D for their ability to produce estimates of physical activity-related energy expenditure (PAEE) in overweight/obese adults. PAEE estimates from both accelerometers were obtained in two experiments. In Experiment 1, 13 overweight/obese subjects (BMI 34.2+/-6.4 kg/m2) were monitored over 2 weeks in everyday life, PAEE being simultaneously measured by the doubly labeled water method (DLW). In Experiment 2, 8 overweight/obese subjects (BMI 34.3+/-5.0 kg/m2) and 10 normal-weight subjects (BMI 20.8+/-2.1 kg/m2) were monitored during a treadmill walking protocol, PAEE being simultaneously measured by indirect calorimetry. In Experiment 1, there was no significant difference between methods in mean PAEE (DLW: 704+/-223 kcal/d, RT3: 656+/-140 kcal/d, TriTrac-R3D 624+/-419 kcal/d). The relative difference between methods (accelerometer vs. DLW) was -17.1%+/-16.7% for the RT3 and -20.0+/-44.6% for the TriTrac-R3D. Correlation for PAEE between RT3 and DLW was higher than between TriTrac-R3D and DLW (r=0.67, p<0.05 and r=0.36, p=0.25, respectively). The 95% confidence interval (CI) (kcal/d) of the mean difference between methods was large, amounting to -385 to 145 for the RT3 and -887 to 590 for the TriTrac-R3D. In Experiment 2, both accelerometers were sensitive to the changes in treadmill speed, with no significant difference in mean PAEE between methods in overweight/obese subjects. Although both accelerometers did not provide accurate estimates of PAEE at individual levels, the data suggest that RT3 has the potential to assess PAEE at group levels in overweight/obese subjects.