Validation of MET estimates and step measurement using the ActivPAL physical activity logger

J Sports Sci. 2011 Mar;29(6):627-33. doi: 10.1080/02640414.2010.549499.


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.

Publication types

  • Validation Study

MeSH terms

  • Actigraphy / methods*
  • Adolescent
  • Adult
  • Basal Metabolism
  • Calorimetry, Indirect
  • Energy Metabolism*
  • Exercise / physiology*
  • Female
  • Humans
  • Locomotion / physiology*
  • Metabolic Equivalent / physiology*
  • Physical Exertion / physiology
  • Reproducibility of Results
  • Walking / physiology*
  • Young Adult