Kenneth R Fox

Charting the physical activity patterns of contemporary children and adolescents

The impact of physical inactivity on health is well accepted throughout the medical and health service community. However, the case has largely been established through epidemiological studies with adults. Substantial attention has been paid to the activity levels of children and adolescents, largely because of changing lifestyles that have threatened the opportunity to be active and also introduced attractive sedentary alternatives such as playing computer games. The research evidence that children have become less active to the point where it is seriously damaging their current and future health has been difficult to establish. This situation is due to difficulties in establishing sensitive health risk markers, and also with the assessment of the different elements of physical activity which in children and adolescents is a complex profile of social behaviours. Self report of activity is unreliable with young children, and objective measures are required that are cheap and effective with large samples and that are capable of measuring levels, volume and patterns of physical activity. Accelerometry in combination with diaries offers the best current solution for most activity-health relationships, and for informing intervention need and design.

Assessment of abdominal fat development in young adolescents using magnetic resonance imaging.

OBJECTIVE: To determine the patterns of change and the best anthropometric indicators of intra-abdominal fat deposition in young adolescents from ages 11–13u2005y.SUBJECTS: Subjects were 25 boys (mean age 13.7±0.32u2005y) and 17 girls (mean age of 13.7±0.23u2005y) who had taken part in a similar study 2u2005y earlier at ages 11.5±0.33u2005y and 11.5±0.27u2005y, respectively.METHODS: Intra-abdominal (IA) and subcutaneous adipose (SA) tissue areas and IA/SA ratio were determined through four tranverse magnetic resonance imaging scans on two occasions. Differences were investigated using t-tests and ANOVA. Skinfolds, girths and circumferences, body mass index and hydrostatic weighing were also recorded. Pearson correlation coefficients and regression equations were calculated to determine the best anthropometric indicators of intra-abdominal fat deposition.RESULTS: Intra-abdominal fat and subcutaneous fat areas had significantly increased in boys and girls by the second measure. Boys had deposited greater amounts of fat in intra-abdominal depots so that their intra-abdominal/subcutaneous ratio had increased significantly from 0.31 to 0.39. This had reduced in girls from 0.39 to 0.35. However, patterns of change were variable within sexes. Truncal skinfold sites (r=0.54–0.70) emerged as the best field indicators of intra-abdominal fat deposition.CONCLUSIONS: Patterns of intra-abdominal and subcutaneous fat distribution are identifiable in pubescent children using magnetic resonance imaging. An acceptable indication is provided by truncal skinfolds.