Combining GPS with heart rate monitoring to measure physical activity in children: A feasibility study.

The recent development of global positioning system (GPS) receivers with integrated heart rate (HR) monitoring has provided a new method for estimating the energy expenditure associated with children's movement. The purpose of this feasibility study was to trial a combination of GPS surveillance and HR monitoring in 39 primary-aged children from New Zealand. Spatial location and HR data were recorded during a school lunch break using an integrated GPS/HR receiver (1Hz). Children averaged a total distance of 1.10+/-0.56km at speeds ranging from 0 to 18.6kmh(-1). Activity patterns were characterised by short bursts of moderate to high speeds followed by longer periods of slow speeds. In addition, boys averaged higher speeds than girls (1.77+/-0.62kmh(-1) and 1.36+/-0.50kmh(-1), respectively; p=0.003). The percentage of time spent at 0kmh(-1) (stationary) ranged from 0.1% to 21.3% with a mean of 6.4+/-4.6%. These data suggest that while children were relatively active during the lunch period, they spent a substantial portion of time engaged in slow or stationary physical activities. Furthermore, associations between HR, average speed, and stationary time demonstrated that children who moved at faster speeds expended more energy than those who moved at slower speeds. We conclude that the combined approach of GPS and HR monitoring is a promising new method for investigating children's play-related energy expenditure. There is also scope to integrate GPS data with geographic information systems to examine where children play and accumulate physical activity.