Validity of the iPhone M7 motion co-processor as a pedometer for able-bodied ambulation. Issue 23 (1st December 2016)

• Record Type: Journal Article
• Authors: Major, Matthew J.; Alford, Micah
• Is Part Of: Journal of sports sciences. Volume 34:Issue 23(2016)
• Page Start: 2160
• Page End: 2164
• Publication Date: 2016-12-01
• Subjects: Physical activity -- smartphone -- walking -- accelerometer; Sports -- Periodicals; Sports -- Physiological aspects -- Periodicals; Sports -- Psychological aspects -- Periodicals; 612.044
• DOI: 10.1080/02640414.2016.1189086
• Languages: English
• ISSNs: 0264-0414

Abstract

ABSTRACT: Physical activity benefits for disease prevention are well-established. Smartphones offer a convenient platform for community-based step count estimation to monitor and encourage physical activity. Accuracy is dependent on hardware–software platforms, creating a recurring challenge for validation, but the Apple iPhone® M7 motion co-processor provides a standardised method that helps address this issue. Validity of the M7 to record step count for level-ground, able-bodied walking at three self-selected speeds, and agreement with the StepWatch TM was assessed. Steps were measured concurrently with the iPhone® (custom application to extract step count), StepWatch TM and manual count. Agreement between iPhone® and manual/StepWatch TM count was estimated through Pearson correlation and Bland-Altman analyses. Data from 20 participants suggested that iPhone® step count correlations with manual and StepWatch TM were strong for customary (1.3 ± 0.1 m/s) and fast (1.8 ± 0.2 m/s) speeds, but weak for the slow (1.0 ± 0.1 m/s) speed. Mean absolute error (manual–iPhone®) was 21%, 8% and 4% for the slow, customary and fast speeds, respectively. The M7 accurately records step count during customary and fast walking speeds, but is prone to considerable inaccuracies at slow speeds which has important implications for certain patient groups. The iPhone® may be a suitable alternative to the StepWatch TM for only faster walking speeds.