title: Validation of MET estimates and step measurement using the ActivPAL physical activity logger.
abstract: The purpose of this study was to determine the validity of the metabolic equivalent (MET) equation and step rate function of the ActivPAL™ physical activity logger in a group of females. Using a standard treadmill protocol, 62 females aged 15-25 years walked on a treadmill at speeds between 3.2 and 7.0 km · h(-1) while wearing an ActivPAL. Oxygen consumption was measured using expired gas analysis at each speed and METs for each speed were estimated based on each participant's own resting metabolic rate. A sub-set of 18 participants also wore an Actigraph. Results showed that the in-built equation in the ActivPAL significantly underestimated (P < 0.001) METs under treadmill conditions at higher intensities. The ActivPAL equation is based on step rate yet the relationship between counts and measured METs (r = 0.76; P < 0.001) is stronger than that between steps and measured METs (r = 0.59; P < 0.001). Both the ActivPAL and Actigraph step functions showed no significant difference (P > 0.05) to video recorded step rate except at the slowest walking speed where the Actigraph significantly underestimated steps (P < 0.05). The development of a new equation based on the counts-METs relationship that includes a variety of speeds and activities would be useful. The ActivPAL step function performs better than the Actigraph at the slowest walking speed under treadmill conditions.
authors.affiliation: Department of Physical Education and Sport Sciences, University of Limerick, Limerick, Ireland.
authors.forename: Deirdre M
authors.initials: DM
authors.lastname: Harrington
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Welk
authors.forename: Alan E
authors.initials: AE
authors.lastname: Donnelly
mesh_terms: D056044:Actigraphy / Q000379:methods*; D000293:Adolescent; D000328:Adult; D001481:Basal Metabolism; D002153:Calorimetry, Indirect; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D055686:Metabolic Equivalent / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D015203:Reproducibility of Results; D016138:Walking / Q000502:physiology*; D055815:Young Adult