title: Reliability and validity of a GPS-enabled iPhone "app" to measure physical activity.
abstract: This study assessed the validity and reliability of an iPhone "app" and two sport-specific global positioning system (GPS) units to monitor distance, intensity and contextual physical activity. Forty (23 female, 17 male) 18-55-year-olds completed two trials of six laps around a 400-m athletics track wearing GPSports Pro and WiSpi units (5 and 1 Hz) and an iPhone(TM) with a Motion X GPS(TM) "app" that used the inbuilt iPhone location services application programming interface to obtain its sampling rate (which is likely to be ≤1 Hz). Overall, the statistical agreement, assessed using t-tests and Bland-Altman plots, indicated an underestimation of the known track distance (2.400 km) and average speed by the Motion X GPS "app" and GPSports Pro while the GPSports WiSpi(TM) device overestimated these outcomes. There was a ≤3% variation between trials for distance and average speed when measured by any of the GPS devices. Thus, the smartphone "app" trialled could be considered as an accessible alternative to provide high-quality contextualised data to enable ubiquitous monitoring and modification of programmes to ensure appropriate intensity and type of physical activity is prescribed and more importantly adhered to.
authors.affiliation: a RMIT University , Discipline of Exercise Sciences, School of Medical Sciences , Australia.
authors.forename: Amanda Clare
authors.initials: AC
authors.lastname: Benson
authors.forename: Lyndell
authors.initials: L
authors.lastname: Bruce
authors.forename: Brett Ashley
authors.initials: BA
authors.lastname: Gordon
mesh_terms: D000293:Adolescent; D000328:Adult; D040421:Cell Phone; D015444:Exercise; D005260:Female; D040362:Geographic Information Systems; D006801:Humans; D008297:Male; D008875:Middle Aged; D063731:Mobile Applications; D009043:Motor Activity; D015203:Reproducibility of Results; D055815:Young Adult
keywords: aerobic exercise; global positioning system; physical activity; reliability and validity; smartphone