The validation of a novel activity monitor in the measurement of posture and motion during everyday activities

P Margaret Grant ^1*, Cormac G Ryan ¹, William W Tigbe ¹ and Malcolm H Granat ¹

¹ Glasgow Caledonian University, United Kingdom

^* To whom correspondence should be addressed. E-mail: m.grant{at}gcal.ac.uk.

Accepted 3 September 2006

Abstract

Background: Accurate measurement of physical activity patterns can be used to identify sedentary behaviour and may facilitate interventions aimed at reducing inactivity.

Objective: To evaluate the activPAL^TM physical activity monitor as a measure of posture and motion in everyday activities using observational analysis as the criterion standard.

Methods: Wearing three activPAL^TM monitors, ten healthy participants performed a range of randomly assigned everyday tasks incorporating walking, standing and sitting. Each trial was captured on a digital camera and the recordings were synchronized with the activPAL^TM. The time spent in different postures was visually classified and this was compared to the activPAL^TM output.

Results: Intraclass Correlation Coefficients (ICC 2,1) for interdevice reliability ranged from 0.79-0.99. Using the Bland and Altman method, the mean percentage difference between the activPAL^TM monitor and observation for total time spent sitting was 0.19% (limits of agreement -0.68% to 1.06%) and total time upright was -0.27% (limits of agreement -1.38% to 0.84%). The mean difference for total time spent standing was 1.4% (limits of agreement -6.2% to 9.1%) and walking was -2.0%, (limits of agreement -16.1% to 12.1%). A second-by-second analysis between observer and monitor found an overall agreement of 95.9%.

Conclusion: The activPAL^TM activity monitor is a valid and reliable measure of posture and motion during everyday physical activities.

Key Words: Accelerometer, Physical activity, Sedentary behaviour, Validity Study

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