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The validity and reliability of a novel activity monitor as a measure of walking
  1. C G Ryan,
  2. P M Grant,
  3. W W Tigbe,
  4. M H Granat
  1. School of Health and Social Care, Glasgow Caledonian University, Glasgow, Scotland, UK
  1. Correspondence to:
 Cormac G Ryan
 School of Health and Social Care, Glasgow Caledonian University, Cowcaddens Road, Glasgow, G4 OBA, UK; cormac.ryan{at}


Background: The accurate measurement of physical activity is crucial to understanding the relationship between physical activity and disease prevention and treatment.

Objective: The primary purpose of this study was to investigate the validity and reliability of the activPAL physical activity monitor in measuring step number and cadence.

Methods: The ability of the activPAL monitor to measure step number and cadence in 20 healthy adults (age 34.5±6.9 years; BMI 26.8±4.8 (mean±SD)) was evaluated against video observation. Concurrently, the accuracy of two commonly used pedometers, the Yamax Digi-Walker SW-200 and the Omron HJ-109-E, was compared to observation for measuring step number. Participants walked on a treadmill at five different speeds (0.90, 1.12, 1.33, 1.56, and 1.78 m/s) and outdoors at three self selected speeds (slow, normal, and fast).

Results: At all speeds, inter device reliability was excellent for the activPAL (ICC (2,1)⩾0.99) for both step number and cadence. The absolute percentage error for the activPAL was <1.11% for step number and cadence regardless of walking speed. The accuracy of the pedometers was adversely affected by slow walking speeds.

Conclusion: The activPAL monitor is a valid and reliable measure of walking in healthy adults. Its accuracy is not influenced by walking speed. The activPAL may be a useful device in sports medicine.

  • cadence
  • measurement
  • physical activity
  • step number
  • walking

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  • Published Online First 6 July 2006

  • Funding: the Glasgow Caledonian University, School of Health and Social Care funded this study and no financial support was received from any commercial company

  • Competing interests: one of the authors is a co-inventor of the activPAL physical activity monitor and a director of PAL Technologies Ltd. However that author was not involved in data collection or the statistical analysis of the results. The remaining authors declare no competing interests

  • Ethics approval: the study procedure was approved by the Glasgow Caledonian University’s School of Health and Social Care Ethics Committee, and all participants provided written informed consent prior to commencement of the study

    Informed consent was obtained for publication of figure 2

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