Accelerometer-Based Activity Measurement in Children

Activity was measured using the ActiGraph GT1M (ActiGraph, Florida, USA), a small (3.8×3.7×1.8 cm), lightweight (27 g) uni-axial accelerometer that measures volumes and patterns of activity. The ActiGraph has been extensively validated in children [26] , [27] , [28] , and is robust when used in large-scale studies in children [3] , [4] , [5] , [8] . A 15-second sampling epoch was selected in order to optimize the ability to capture the sporadic nature of children’s activity [1] . Children were asked to wear the accelerometer on an elasticated belt on the right hip for seven consecutive days during all waking hours, except during bathing or swimming. Accelerometers were posted to families who were asked to return it as soon as possible after the monitoring period using a supplied pre-paid envelope. Accelerometers were distributed between May 2008 and August 2009.
Ethical approval for the MCS accelerometer study was granted by the Northern and Yorkshire Research Ethics Committee (REC number: 07/MRE03/32). The MCS data for surveys 1 to 4 are currently available via the Economic and Social Data Service; the MCS accelerometer data will be also be available shortly at the beginning of 2013.