Equivalence Reliability and Validity of the Tritrac and RT3 Triaxial Accelerometers in Youth

Abstract

0208 Accelerometry is a promising approach for the assessment of movement and energy expenditure. The RT3 Research Tracker is the newer generation of the Tritrac-R3D triaxial accelerometer. PURPOSE: The purpose of this study was to examine the equivalence reliability and validity of the RT3 and Tritrac in girls aged 12- to 14-years. METHODS: Sixty girls completed three 5-minute bouts on a treadmill at self-selected speeds (walk, brisk walk, jog). Submaximal VO2 at each speed and VO2 max (mean = 41.4 ± 7.3 ml.kg−1·min−1) were assessed using a ParvoMedics 2400 system. An RT3 and a Tritrac were randomly selected from a sample of monitors and worn in a hip pack during the treadmill tests. For correlational analyses over all speeds, one speed was randomly selected for each subject. RESULTS: The intraclass correlation (ICC) between the RT3 and Tritrac was .98 over all speeds (.55 for walking, .78 for brisk walking, .18 for jogging). Measured energy expenditure and activity counts from the RT3 (r = .86) and from the Tritrac (r = .84) were highly correlated. Regression equations to estimate energy expenditure (kcal·min−1) from activity counts and body mass were developed. For the RT3 equation, R2 = .86, SEE = 0.84 kcal·min−1. For the Tritrac equation, R2 = .81, SEE = 0.94 kcal·min−1. These values compare favorably to the SEEs for energy expenditure estimated directly from the monitors (RT3 SEE = 1.77 kcal·min−1; Tritrac SEE = 1.24 kcal·min−1). Activity counts corresponding to light (< 3 METs), moderate (3 to 6 METs), and vigorous (> 6 METs) intensity activity were estimated from regression equations. For the RT3: light is < 1313, moderate is 1313 to 3372, vigorous is > 3372 counts·min−1. For the Tritrac: light is < 1009, moderate is 1009 to 2618, vigorous is > 2618 counts·min-1. CONCLUSIONS: The RT3 and Tritrac accelerometers have high relative correspondence, but poor absolute correspondence (i.e., the RT3 records higher activity counts than the Tritrac). Both accelerometers provide accurate estimates of energy expenditure from treadmill exercise.