Use of global positioning systems to study physical activity and the environment: a systematic review.
BACKGROUND
The GPS represents an innovative way to objectively assess the spatial locations of physical activity behavior. The aim of this systematic review was to determine the capability of GPS to collect high-quality data on the location of activities in research on the relationship between physical activity and the environment.


METHODS
Published and unpublished articles identified from seven electronic databases, reference lists, bibliographies, and websites up to March 2010 were systematically searched for, appraised, and analyzed in summer 2010. Included studies used GPS to measure the spatial locations of physical activity and some form of environmental analysis related to the GPS data. The capability of GPS was expressed in terms of data quality, which in turn was defined as the proportion of GPS data lost in each study.


RESULTS
24 studies met the inclusion criteria. Data loss was positively correlated with the measurement period for which participants were asked to wear the GPS device (r=0.81, p<0.001). Major reasons for data loss included signal drop-outs, loss of device battery power, and poor adherence of participants to measurement protocols. Data loss did not differ significantly between children and adults or by study sample size, year of publication, or GPS device manufacturer.


CONCLUSIONS
GPS is a promising tool for improving understanding of the spatial context of physical activity. The current findings suggest that the choice of an appropriate device and efforts to maximize participant adherence are key to improving data quality, especially over longer study periods.
Institute of Sport Science, University of Graz, Austria. patricia.krenn@gmx.net
Patricia J
PJ
Krenn
Sylvia
S
Titze
Pekka
P
Oja
Andrew
A
Jones
David
D
Ogilvie
D000328:Adult; D002648:Child; D004777:Environment; D040362:Geographic Information Systems; D006801:Humans; D009043:Motor Activity; D012107:Research Design; D012111:Residence Characteristics; D013997:Time Factors