A Study into the Reliability of the Data Flow from GPS Enabled Portable Fitness Devices to the Internet

The growth in availability and affordability of portable fitness devices (PFDs) has facilitated a concomitant growth in the collection and sharing of what are assumed to be reliable measures of exercise and physical activity. This data is increasingly used by fitness trainers to track performance progression, and plan training. Whilst the reliability and validity of these devices has been reported, investigation into the variance in the data at different access points is less well examined. The aim of this study was to investigate the reliability of the data flow from global positioning system enabled portable fitness devices, to the Internet, at multiple access points. Fifteen participants undertook four trials of two laps around a non-linear track (approximately 2350m per lap), at a self-determined pace, whilst wearing a PFD. Data was retrieved for comparison from three access points; a file recorded by the device, manually recorded data from the Internet, and a file retrieved from the Internet. There was no significant difference between the distance (p=0.98) and time (p=0.99) at any of the three points of access. However, recordings of elevation gain and loss were significantly different when compared across the three access points (p<0.05). It can be concluded from this study that the data flow from the PFDs used reliably reported the distance and time recorded at multiple access points, but the same was not true of the elevation gain and loss. Caution should be advised when comparing activity data from multiple access points to indicate performance progression or inform training plans.