Validity and reliability of measuring activities, movement intensity and energy expenditure with the DynaPort...

The purpose of this study was to evaluate the validity and reliability of assessing activities, movement intensity (MI) and energy expenditure (EE) measured by accelerometry. 28 Able-bodied participants performed standardized tasks while an accelerometer was worn and oxygen uptake was measured. After uploading the accelerometer data to the manufacturer's website, a report was received that gave minute-by-minute MI and EE of the performed activities. Validity was assessed by comparing reported activities and EE with the actual performed activities and calculated EE from the oxygen uptake, and by testing whether MI differed between walking velocities and cycling resistances. Reliability was assessed by performing the protocol twice. Except for standing (classified predominantly (82%) as sitting), most activities were categorized mainly correctly (93-100%). A difference in MI was detected between walking speeds but not between cycling resistances. EE was overestimated for walking (ICC=0.54) and underestimated for cycling (ICC=0.03). Reliability of MI was high (ICC=0.91) but reliability for the relative time spent in activities or the step count was weak to moderate. In conclusion, most activities were categorized correctly, MI seemed to be valid and reliable but reliability is low for relative time spent in activities and EE cannot be estimated well.