Research Output

Validity of the iPhone M7 Motion Coprocessor to Estimate Physical Activity During Structured and Free-Living Activities in Healthy Adults

  Modern smartphones such as the iPhone contain an integrated accelerometer, which can be used to measure body movement and estimate the volume and intensity of physical activity. Objectives: The primary objective was to assess the validity of the iPhone to measure step count and energy expenditure during laboratory-based physical activities. A further objective was to compare free-living estimates of physical activity between the iPhone and the ActiGraph GT3X+ accelerometer. Methods: Twenty healthy adults wore the iPhone 5S and GT3X+ in a waist-mounted pouch during bouts of treadmill walking, jogging, and other physical activities in the laboratory. Step counts were manually counted, and energy expenditure was measured using indirect calorimetry. During two weeks of free-living, participants (n = 17) continuously wore a GT3X+ attached to their waist and were provided with an iPhone 5S to use as they would their own phone. Results: During treadmill walking, iPhone (703 ± 97 steps) and GT3X+ (675 ± 133 steps) provided accurate measurements of step count compared with the criterion method (700 ± 98 steps). Compared with indirect calorimetry (8 ± 3 kcal·min−1), the iPhone (5 ± 1 kcal·min−1) underestimated energy expenditure with poor agreement. During free-living, the iPhone (7,990 ± 4,673 steps·day−1) recorded a significantly lower (p

  • Type:

    Article

  • Date:

    25 June 2021

  • Publication Status:

    Published

  • Publisher

    Human Kinetics

  • DOI:

    10.1123/jmpb.2020-0067

  • Cross Ref:

    10.1123/jmpb.2020-0067

  • ISSN:

    2575-6605

  • Funders:

    Edinburgh Napier Funded

Citation

Thomson, N. K., McMichan, L., Macrae, E., Baker, J. S., Muggeridge, D. J., & Easton, C. (2021). Validity of the iPhone M7 Motion Coprocessor to Estimate Physical Activity During Structured and Free-Living Activities in Healthy Adults. Journal for the Measurement of Physical Behaviour, 4(3), 212-219. https://doi.org/10.1123/jmpb.2020-0067

Authors

Keywords

accelerometer; energy expenditure; GT3X+; step count; smartphone; validation; walking

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