Distance running is a tremendously popular sport/fitness activity amongst US adults. Individualizing training volume (i.e., distance) is necessary to optimize training responses and reduce injury risk. While personal global positioning satellite (GPS) devices are a validated means of accurately measuring distance, the validity of distance measurements by accelerometer-based physical activity monitors is unknown.
PURPOSE: Assess the concurrent validity and agreement of distance measurements by a commercially-available physical activity monitor to those of a personal GPS device during self-paced running.
METHODS: Twenty-four recreational runners (n = 12 females) wore a personal GPS (Garmin ForeRunner 10, GPS) and commercially-available physical activity monitor (MOVband accelerometer, MB) on the dominant wrist during three separate outdoor training runs. Participants followed their normal training schedules, such that the pace and duration of each run was voluntarily determined by the participant. The association between MB and GPS distance measurements was determined using Pearson’s correlation analysis. The 95% limits of agreement between MB and GPS were calculated according to the method of Bland and Altman. Specifically, the upper and lower limits of agreement were calculated as the mean of the differences (d) between GPS and MB ± (1.96 x the standard deviation of the differences), expressed as: d ± 1.96s.
RESULTS: There was a significant, positive association of a large effect size between measurements of distance by GPS and the commercially-available physical activity monitor (MB) (r = 0.763, p < 0.001). However, the calculated limits of agreement (-1.946 to 2.025km) between GPS and accelerometer measurements suggest that individual MB measurements may be up to 2km above or below GPS.
CONCLUSION:We suggest that non-GPS distance measurements by commercially-available physical activity monitors may be useful for monitoring overall, cumulative volume for health and fitness purposes. However, these measurements fall short of GPS when high accuracy is needed, as in training programs designed to enhance performance. These findings cannot be generalized to all accelerometer devices.