title: Global positioning system watches for estimating energy expenditure.
abstract: Global positioning system (GPS) watches have been introduced commercially, converting frequent measurements of time, location, speed (pace), and elevation into energy expenditure (EE) estimates. The purpose of this study was to compare EE estimates of 4 different GPS watches (Forerunner, Suunto, Polar, Adeo), at various walking speeds, with EE estimate from a triaxial accelerometer (RT3), which was used as a reference measure in this study. Sixteen healthy young adults completed the study. Participants wore 4 different GPS watches and an RT3 accelerometer and walked at 6-minute intervals on an outdoor track at 3 speeds (3, 5, and 7 km/hr). The statistical significance of differences in EE between the 3 watches was assessed using linear contrasts of the coefficients from the overall model. Reliability across trials for a given device was assessed using intraclass correlation coefficients as estimated in the mixed model. The GPS watches demonstrated lower reliability (intraclass correlation coefficient) across trials when compared with the RT3, particularly at the higher speed, 7 km/hr. Three GPS watches (Forerunner, Polar, and Suunto) significantly and consistently underestimated EE compared with the reference EE given by the RT3 accelerometer (average mean difference: Garmin, -50.5%; Polar, -41.7%; and Suunto, -41.7%; all p < 0.001). Results suggested that caution should be exercised when using commercial GPS watches to estimate EE in athletes during field-based testing and training.
authors: 1Department of Nutritional Sciences, the University of Arizona, Tucson, Arizona; 2Office of Arid Lands Studies, School of Natural Resources and the Environment, The University of Arizona, Tucson, Arizona; 3Mel and Enid Zuckerman College of Public Health, The University of Arizona, Tucson, Arizona; and 4Biostatistics and Director of Biometry, The University of Arizona, Public Health, Tucson, Arizona.
authors: Nobuko
authors: N
authors: Hongu
authors: Barron J
authors: BJ
authors: Orr
authors: Denise J
authors: DJ
authors: Roe
authors: Rebecca G
authors: RG
authors: Reed
authors: Scott B
authors: SB
authors: Going
mesh_terms: D061725:Accelerometry; D000328:Adult; D004734:Energy Metabolism; D005260:Female; D040362:Geographic Information Systems / Q000295:instrumentation*; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D016138:Walking / Q000502:physiology*; D055815:Young Adult