Technical Variability of the RT3 Accelerometer

Abstract

There were no differences in counts recorded on the X, Y, and Z axes at 2.1 Hz; however, the counts recorded along the Y axis were significantly higher than the counts at the X and Z axes at 5.1 and 10.2 Hz. Due to large coefficients of variation for both inter- and intra-instrument variability at 2.1 Hz, testing the inter- and intra-instrument variability of the accelerometers before use is recommended.

Selection, Use and Psychometric Properties of Physical Activity Measures to Assess Individuals with Severe Mental Illness: A Narrative Synthesis

“…The methodological criteria were developed according to previous detailed procedures (Janney, 2012;Powell, Jones, & Rowlands, 2003;Powell & Rowlands, 2004;Rowlands, Thomas, Eston, & Topping, 2004;Sharpe, 2007;. Based on this a set of criteria were established for the included studies.…”

“…Accelerometers (notably the RT3) have been used as the criterion measure, despite the caution of their use and accuracy in determining activity energy expenditure (Sharpe et al, 2006a) and errors generated by equations used to categorize and define physical activity in OBM (Prince et al, 2008). The RT3 is suggested to be an appropriate criterion measure (Eston, Rowlands, & Ingledew, 1998;Powell & Rowlands, 2004;Powell et al, 2003) and sensitive in capturing and distinguishing time spent at different intensities of physical activity Yamamoto et al, 2011).…”

Construct validity of RT3 accelerometer: A comparison of level-ground and treadmill walking at self-selected speeds

“…The RT3 accelerometer measures acceleration periodically and converts it to a digital representation, which is then processed to obtain an "activity count" and stored in the memory. The exact relationship of the activity count to the acceleration (measured in meters per second squared or g, where 1 g = 9.81 m/s 2 ) is not clear [19].…”

“…We pretested the two RT3 accelerometers employed in this study using a motorized vibration table that produced a frequency of 3.3 Hz with a calculated mean acceleration of 0.74 g, which is within the dynamic range of the RT3 accelerometer [19] and the range of accelerations expected during level-ground and treadmill walking [34]. We placed each RT3 accelerometer on the x-, y-, and z-axis on the table and tested them for 5 minutes, repeated six times on each axis.…”

“…Validation and reliability of the RT3 accelerometer for free-living research has been assessed under a number of laboratory-based conditions, including walking and running at standardized speeds on a treadmill [11,[14][15][16][17], using a shaker table [18][19], assessing various mobility tasks [3], and performing structured activities [20]. A recent study has also demonstrated the ability of the RT3 accelerometer to discriminate between a series of standardized laboratory-based activities [21]; however, the ability of RT3 accelerometer vector magnitude (VM) counts to discriminate specific activities in free living has yet to be established.…”