Validity of physical activity monitors in adults participating in free living activities

¹ Norwegian School of Sport Sciences, Norway
² Ullevaal University Hospital, Norway
³ Norwegian School of Sports Sciences, Norway
⁴ University of Oslo, Norway
⁵ Norwegian University of Sport and PE, Norway

^* To whom correspondence should be addressed. E-mail: sveinung.berntsen{at}nih.no.

Accepted 1 July 2008

	Abstract

Background: For a given subject, time in moderate to very vigorous intensity physical activity (MVPA) varies substantially among physical activity monitors.

Objective: The primary objective of the present study was to determine whether time in MVPA recorded with SenseWear^TM Pro2 Armband (Armband), ActiGraph, ikcal and ActiReg® is different compared to indirect calorimetry. The secondary objective was to determine whether these activity monitors estimate energy expenditure different compared to indirect calorimetry.

Material and methods: Fourteen men and six women wore the activity monitors and a portable oxygen analyzer for 120 minutes doing a variety of activities of different intensities. Resting metabolic rate (RMR) was measured with indirect calorimetry. The cut off points defining moderate, vigorous and very vigorous intensity were 3, 6 and 9 times RMR.

Results: Armband and ActiGraph overestimated time in MVPA by 2.9 and 2.5% and ikcal and ActiReg® underestimated time in MVPA by 11.6 and 98.7%, respectively. ActiReg® (p=0.004) and ActiGraph (p=0.007) underestimated energy expenditure in MVPA and all monitors underestimated total energy expenditure (by 5 to 21%). Conclusions: Recorded time in MVPA and energy expenditure varies substantially among physical activity monitors. Thus, when comparing physical activity level among studies, it is essential to know the type of physical activity monitor being used.