title: Metabolic Power Method: Underestimation of Energy Expenditure in Field-Sport Movements Using a Global Positioning System Tracking System.
abstract: The purpose of this study was to assess the validity of a global positioning system (GPS) tracking system to estimate energy expenditure (EE) during exercise and field-sport locomotor movements. Twenty-seven participants each completed a 90-min exercise session on an outdoor synthetic futsal pitch. During the exercise session, they wore a 5-Hz GPS unit interpolated to 15 Hz and a portable gas analyzer that acted as the criterion measure of EE. The exercise session was composed of alternating 5-minute exercise bouts of randomized walking, jogging, running, or a field-sport circuit (×3) followed by 10 min of recovery. One-way analysis of variance showed significant (P < .01) and very large underestimations between GPS metabolic power- derived EE and oxygen-consumption (VO2) -derived EE for all field-sport circuits (% difference ≈ -44%). No differences in EE were observed for the jog (7.8%) and run (4.8%), whereas very large overestimations were found for the walk (43.0%). The GPS metabolic power EE over the entire 90-min session was significantly lower (P < .01) than the VO2EE, resulting in a moderate underestimation overall (-19%). The results of this study suggest that a GPS tracking system using the metabolic power model of EE does not accurately estimate EE in field-sport movements or over an exercise session consisting of mixed locomotor activities interspersed with recovery periods; however, is it able to provide a reasonably accurate estimation of EE during continuous jogging and running.
authors.forename: Darcy M
authors.initials: DM
authors.lastname: Brown
authors.forename: Dan B
authors.initials: DB
authors.lastname: Dwyer
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Robertson
authors.forename: Paul B
authors.initials: PB
authors.lastname: Gastin
mesh_terms: D002153:Calorimetry, Indirect; D004734:Energy Metabolism; D004867:Equipment Design; D005260:Female; D040362:Geographic Information Systems / Q000295:instrumentation*; D006801:Humans; D007590:Jogging; D008297:Male; D009043:Motor Activity; D009119:Muscle Contraction; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D020127:Recovery of Function; D015203:Reproducibility of Results; D012420:Running; D013997:Time Factors; D013996:Time and Motion Studies; D016138:Walking; D055815:Young Adult
keywords: criterion validity; energy cost; excess postexercise oxygen consumption; intermittent exercise; time–motion analysis