The validity and reliability of a novel activity monitor as a measure of walking

Cormac G Ryan ^1*, P Margaret Grant ¹, William Wiewatenni Tigbe ¹ and Malcolm H Granat ¹

¹ Glasgow Caledonian University, United Kingdom

^* To whom correspondence should be addressed. E-mail: cormac.ryan{at}gcal.ac.uk.

Accepted 22 June 2006

Abstract

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^TM physical activity monitor in measuring step number and cadence.

Methods: The ability of the activPAL^TM monitor to measure step number and cadence in 20 healthy adults (age 34.5 ± 6.9; BMI 26.8 ± 4.8 [mean ± SD]) was evaluated against video observation. Concurrently, the accuracy of two commonly used brands of pedometers, the Yamax Digi-Walker SW-200 and 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 1.78m.s^-1) and outdoors at three self-selected speeds (slow, normal and fast).

Results: At all speeds, inter device reliability was excellent for the activPAL^TM (ICC 2,1 0.99) for both step number and cadence. The absolute percentage error for the activPAL^TM 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^TM monitor is a valid and reliable measure of walking in healthy adults. Its accuracy is not influenced by walking speed. The activPAL^TM may be a useful device in sports medicine.

Key Words: cadence, physical activity, step number, validity, walking

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