Cross-validation of Actigraph derived accelerometer cut-points for assessment of sedentary behaviour and physical activity in children aged 8-11 years.

AIM: To cross-validate previously calibrated Actigraph cut-points in children. METHODS: Twenty-eight children (50% boys) aged between 8 and 11 years of age (9.4 ± 1.4 years) performed a series of 5 minute bouts of activity reflective of different levels of PA from sedentary behaviour (SB) to moderate to vigorous physical activity (MVPA); V˙ O2 was assessed using breath-by-breath indirect calorimetry, and activity was assessed using Actigraph accelerometers worn on the hip and non-dominant wrist. The V˙ O2 values were then converted into age-specific METs (measured METs) and coded as SB, light PA and MVPA. Accelerometer data were analysed using previously calibrated cut-points at different epochs, that is 5, 15, 30 and 60 seconds. RESULTS: Receiver operating characteristic (ROC) curve analysis indicated that there was excellent discrimination of SB using the Evenson et al (15 seconds), Romanzini (15 seconds), Treuth et al (30 seconds), Freedson et al (60 seconds), Treuth et al (60 seconds) and Troiano et al (60 seconds) cut-points. ROC analysis indicated poor discrimination for LPA irrespective of the cut-points used. Good discrimination of MVPA was evident for all existing cut-points using a 60-second epoch. CONCLUSION: There is considerable variation in the performance of existing cut-points for assessment of SB, LPA and MPA in children.

Environmental and school influences on physical activity in South Asian children from low socio-economic backgrounds: A qualitative study.

South Asian (SA) children are less active but have enhanced metabolic risk factors. Physical activity (PA) is a modifiable risk factor for metabolic disease. Evidence suggests that environmental factors and socio-economic status influence PA behaviour. The purpose of this study was to understand PA environments, barriers and facilitators of PA in deprived environments for children from SA backgrounds. Focus groups were conducted with 5 groups of children aged 7-9 years (n = 33; male = 16, female = 17; SA = 17, White = 8 and Black = 8) from two schools in deprived wards of Coventry, England. Thematic analysis was used to identify key themes and subthemes across all transcripts. From the results, emergent themes included school and home environment, outdoor activity, equipment, weather, parental constraints and safety. Ethnic differences were apparent for sources of beliefs and knowledge and religious practice as constraints for PA. The findings suggest that school provides a good foundation for PA attitude, knowledge and behaviour, especially for SA children. To increase PA, multi-component interventions are needed, which focus on changing the home environment (i.e. junk food and media time), encouraging outdoors activity, changing perceptions of safety and weather conditions, which provide parental constraints for children. Interventions also need to be considerate to religious practices that might constrain time.