Children's physical activity assessed with wrist- and hip-worn accelerometers.
BACKGROUND
Recently, triaxial raw acceleration accelerometers have become available from GENEActiv and ActiGraph; both are designed for wrist and hip wear. It is important to determine whether the output from these monitors is comparable with the wealth of data already collected from the hip-worn, epoch-based, uniaxial ActiGraph.


OBJECTIVE
This study aimed to assess the concurrent validity of measures of total activity and time spent at different activity intensities from the GENEActiv relative to the ActiGraph GT3X+.


METHODS
Fifty-eight children age 10-12 yr wore two accelerometers at the hip (ActiGraph GT3X+ and GENEActiv) and one at the wrist (GENEActiv) for 7 d. Wear time was matched for all monitors before analysis.


RESULTS
Mean daily accelerometer output, time spent sedentary, and time in moderate-to-vigorous physical activity (MVPA) from the hip- or wrist-worn GENEActiv were strongly correlated with the corresponding output from the hip-worn ActiGraph (r > 0.83, P < 0.001). However, less time was estimated to be sedentary and more time was estimated to be MVPA using the hip- or wrist-worn GENEActiv (Phillips cut points) than that when using the Evenson vertical axis cut points with the hip-worn ActiGraph. Output from the vertical axis ActiGraph cut points could be predicted with 95% limits of agreement, equating to 23%-28% and 33%-35% of the mean value, by the hip- and wrist-worn GENEActiv, respectively.


CONCLUSIONS
The assessment of children's activity level, time spent sedentary, and time in MVPA estimated from the hip- or wrist-worn GENEActiv seems to be comparable with that of the uniaxial ActiGraph. On the basis of the strong linear correlations, ActiGraph output can be predicted from the hip- or wrist-worn GENEActiv for comparative purposes at the group level. However, because of relatively wide limits of agreement, individual-level comparisons are not recommended.
1Health and Use of Time Group, Sansom Institute for Health Research, Division of Health Sciences, University of South Australia, Adelaide, South Australia, AUSTRALIA; 2Exercise for Health and Human Performance Group, Sansom Institute for Health Research, Division of Health Sciences, University of South Australia, Adelaide, South Australia, AUSTRALIA; 3Centre for Lifespan and Chronic Illness Research, School of Life and Medical Sciences, Department of Human and Environmental Sciences, University of Hertfordshire, Hertfordshire, UNITED KINGDOM; and 4Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, Devon, UNITED KINGDOM.
Alex V
AV
Rowlands
Kirsten
K
Rennie
Robert
R
Kozarski
Rebecca M
RM
Stanley
Roger G
RG
Eston
Gaynor C
GC
Parfitt
Tim S
TS
Olds
D056044:Actigraphy / Q000295:instrumentation*; D002648:Child; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D015203:Reproducibility of Results; D057185:Sedentary Behavior; D013997:Time Factors