Reliability and Validity of Accelerometer Devices when used to Detect Differences in Activity Intensity and Estimate Energy Expenditure in Lean and Overweight Adults

Reliability and validity of accelerometer devices when used to detect differences in activity intensity and estimate energy expenditure in lean and overweight adults. Khalid S. AlJaloud, Adrienne R. Hughes, Stuart D.R. Galloway. Health and Exercise Science Research Group, School of Sport, University of Stirling, FK9 4LA. SCOTLAND, U.K.

Introduction Many devices are available for monitoring of free living physical activity. These devices can detect movement but also posture or physiological variables such as heart rate or heat flux. More information is required on the reliability and validity of these devices under laboratory conditions to judge their value as free living activity monitoring tools.

Methods 61 adults (n= 30 lean and n= 31 overweight/obese) attended for 3 lab sessions. On the first session body mass, height, BMI, body fat and resting heart rate (HR) were recorded, and familiarisation with equipment and procedures was performed. On the 2nd session they were instrumented with three accelerometer devices (ActiGraph, ActivPAL and SenseWear Pro) and then asked to walk on a treadmill at three speeds (3km/h, 4.5km/h and 6km/h) for 5 minutes each at 0% grade. After a 10 min seated recovery period these speeds were replicated on an incline (5% grade). This protocol was repeated on the 3rd session. HR, indirect calorimetry (for energy expenditure determination) and outputs from the three accelerometer devices were recorded throughout.

Results All accelerometers were reliable on the flat and on an incline across all speeds. ActiGraph, ActivPAL and SenseWear Pro gave strong intra-instrument reliability (ICC) r= 0.99, r= 0.99 and r= 0.96.

Conclusion All of the studied devices are reliable. The ActiGraph and SenseWear Pro were also sensitive enough to detect differences in activity intensity across all speeds examined. ActivPAL could detect differences in activity intensity for lean but not for overweight / obese adults. None of the devices could accurately quantify energy expenditure across all speeds and gradients studied but ActiGraph was considered valid at more speeds on level ground than the other devices. Caution must be taken when using these devices to measure differences in activity intensity or energy expenditure in free living situations, particularly in overweight/obese adults.