Validity of wrist worn accelerometers and comparability between hip and wrist placement sites in estimating physical activity behaviour in preschool children

Abstract

Wrist-worn accelerometers can increase compliance with wearing accelerometers, however, several large scale studies continue to use hip-worn accelerometers and it is unclear how comparable data is from the two sites. The study aims were: to investigate agreement between wrist- and hip- worn accelerometers and to determine the validity of Johansson et al cut-points for wrist worn accelerometers in preschool children. A sample of 32 preschool children (21 boys, 4.2 (0.5) years, BMI 16.6 (1.1)) were videoed wearing GT3X+ accelerometers on their wrist and hip while they engaged in 1 h of free-play in their nursery. Children's activity were coded using, the children's activity rating scale (CARS): with CARS, level 1 'sedentary' and levels 2-5 were classified as time spent in total physical activity (TPA). Accelerometry data were processed using Johansson et al cut-points for the wrist data and Evenson et al cut-points for the hip data, into time spent in different intensities of physical activity (PA). The mean counts per minute (cpm) from the hip and wrist were compared. There was a strong correlation between the hip and wrist cpm (r = 0.81, p < 0.01) and total count data (r = 0.83 p < 0.01), however there was a large systematic bias with wide limits of agreement. Good agreement (mean difference (LOA) 1.1 (-9.9, 12.1) was found between the CARS estimate of TPA (29.5 (10.4) mins) and the wrist estimate, using the Johansson et al cut points (28.4 (9.8) mins). There was also a reasonable agreement between the hip estimates with the Evenson et al cut-points and Johansson et al estimate (mean difference (LOA):6.3 (-8.8, 21.4) mins. In conclusion, the findings suggest that the Johansson et al (2013 Pediatr. Obes. 10 1-6) cut-points applied to wrist worn accelerometers provides a valid estimate of TPA in preschool children and have reasonable agreement with Evenson et al cut-points applied to hip accelerometers. 2016 Institute of Physics and Engineering in Medicine.

Paper adds to the growing body of evidence that children can acquire phonological systems before they are able to master the phonetic skills needed to convey the contrasts in that system