title: Validity of actigraphs uniaxial and triaxial accelerometers for assessment of physical activity in adults in laboratory conditions.
abstract: BACKGROUND
  Few studies to date have directly compared the Actigraphs GT1M and the GT3X, it would be of tremendous value to know if these accelerometers give similar information about intensities of PA. Knowing if output is similar would have implications for cross-examination of studies. The purpose of the study was to assess the validity of the GT1M and the GT3X Actigraph accelerometers for the assessment of physical activity against oxygen consumption in laboratory conditions.
  
  
  METHODS
  Forty-two college-aged participants aged 18-25 years wore the GT1M and the GT3X on their right hip during treadmill exercise at three different speeds, slow walking 4.8 km.h-1, fast walking 6.4 km.h-1, and running 9.7 km.h-1). Oxygen consumption was measured minute-by minute using a metabolic system. Bland-Altman plots were used to assess agreement between activity counts from the GT3X and GT1M, and correlations were assessed the ability of the accelerometers to assess physical activity.
  
  
  RESULTS
  Bias for 4.8 km.h-1 was 2814.4 cpm (limits 1211.3 to 4417.4), for 6.4 km.h-1 was 3713.6 cpm (limits 1573.2 to 5854.0), and for 9.7 km.h-1 was-3811.2 cpm (limits 842.1 to 6780.3). Correlations between counts per minute for the GT1M and the GT3X were significantly correlated with VO2 (r = 0.881, p < 0.001; r = 0.810, p < 0.001 respectively).
  
  
  CONCLUSIONS
  The present study showed that both the GT1M and the GT3X accurately measure physical activity when compared to oxygen consumption.
authors.affiliation: Department of Exercise Science, California Lutheran University, 60 W, Olsen Road, #3400, Thousand Oaks, CA 91360, USA. lakelly@callutheran.edu.
authors.forename: Louise A
authors.initials: LA
authors.lastname: Kelly
authors.forename: Duncan Ge
authors.initials: DG
authors.lastname: McMillan
authors.forename: Alexandra
authors.initials: A
authors.lastname: Anderson
authors.forename: Morgan
authors.initials: M
authors.lastname: Fippinger
authors.forename: Gunnar
authors.initials: G
authors.lastname: Fillerup
authors.forename: Jane
authors.initials: J
authors.lastname: Rider