Validity of the iPhone M7 motion co-processor as a pedometer for able-bodied ambulation

Matthew J. Major*, Micah Alford

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


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 StepWatchTM was assessed. Steps were measured concurrently with the iPhone® (custom application to extract step count), StepWatchTM and manual count. Agreement between iPhone® and manual/StepWatchTM count was estimated through Pearson correlation and Bland-Altman analyses. Data from 20 participants suggested that iPhone® step count correlations with manual and StepWatchTM 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 StepWatchTM for only faster walking speeds.

Original languageEnglish (US)
Pages (from-to)2160-2164
Number of pages5
JournalJournal of Sports Sciences
Issue number23
StatePublished - Dec 1 2016


  • Physical activity
  • accelerometer
  • smartphone
  • walking

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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