BACKGROUND: Interest in the quantification of physical activity is on the rise. Triaxial accelerometry has frequently been used; however, research on the reliability of these devices is limited. We examine the interunit and intraunit reliability of 22 RT3 triaxial accelerometers using a performance-documented laboratory agitator. METHODS: The RT3 units were tested while moving in 2 directions (antero-posterior, medio-lateral) and speeds (150 and 275 RPM) on a shaker with simultaneous documented performance output for three 24-hour periods. RESULTS: Minimal shaker variance was recorded for all trials (coefficients of variation [CVs] < 0.52%). Our data demonstrate good reliability within RT3s (CVs < 1.81%) but poor reliability among the 22 units (CVs range = 9.5% to 34.7%). CONCLUSIONS: In longitudinal studies, each subject should use the same RT3 unit at each assessment. The use of multiple RT3 units in cross-sectional studies is not recommended because data interpretation would be compromised by the high between-unit variability.
BACKGROUND: Interest in the quantification of physical activity is on the rise. Triaxial accelerometry has frequently been used; however, research on the reliability of these devices is limited. We examine the interunit and intraunit reliability of 22 RT3 triaxial accelerometers using a performance-documented laboratory agitator. METHODS: The RT3 units were tested while moving in 2 directions (antero-posterior, medio-lateral) and speeds (150 and 275 RPM) on a shaker with simultaneous documented performance output for three 24-hour periods. RESULTS: Minimal shaker variance was recorded for all trials (coefficients of variation [CVs] < 0.52%). Our data demonstrate good reliability within RT3s (CVs < 1.81%) but poor reliability among the 22 units (CVs range = 9.5% to 34.7%). CONCLUSIONS: In longitudinal studies, each subject should use the same RT3 unit at each assessment. The use of multiple RT3 units in cross-sectional studies is not recommended because data interpretation would be compromised by the high between-unit variability.
Authors: Gary D Miller; John M Jakicic; W Jack Rejeski; Melicia C Whit-Glover; Wei Lang; Michael P Walkup; Mimi L Hodges Journal: Obesity (Silver Spring) Date: 2013-01 Impact factor: 5.002
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