Understanding children's independent mobility
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Childhood is a critical developmental period; patterns of physical activity established during this time are likely to track into adolescence and adulthood. Children who are regularly physically active benefit from greater bone mineral density, enhanced motor skills, maintenance of a normal weight status, and risk reduction for a myriad of non-communicable diseases. Insufficient physical activity in children has stimulated widespread investigation into behaviours that can promote or inhibit activity during this important life stage. The ability to play, roam and move unsupervised (independent mobility), is a fundamental behaviour, which provides natural opportunities for habitual physical activity. A proposed decline in children?s independent mobility (IM) has recently gained attention as a likely and important contributor for low activity levels in children. However, comprehensive understanding of this behaviour is presently limited by the absence of standardised measurement techniques. The overarching aim of this thesis was to develop innovative measures of IM to explore intergenerational differences in IM and investigate the associations between IM and physical activity in 10-13-year-old children. An initial pilot study was conducted in Auckland, New Zealand and three different measures of children?s IM were explored with three generations of directly related participants (Chapter 3). Self-reported independent parental licences to travel without an adult (IM Licence) and independent roaming allowances to certain locations (summed to form an index; IM Index) were collected for 45 participants. The third measure was an interactive map to record the self-reported maximum roaming distance from home residence (IM Maximum). Substantial intergenerational differences were observed across all IM measures. Mean IM Maximum travelled by grandparents was 7810m (SD = 7064), which declined to 5335m (SD = 4940) for parents and further reduced to 2673m (SD = 1929) for children. Similarly, IM Index declined from grandparents to parents and even further in children (2.54, SD = 0.70; 2.28, SD = 0.44; 1.49, SD = 0.28; respectively). Differences for both IM Index and IM Maximum were only statistically significant between parents and children, indicating the degree to which this behaviour has recently changed. In regard to IM Licences, only one child was permitted the same completely unrestricted licence to roam and travel freely in the neighbourhood that their parents and grandparents experienced. These findings provided novel evidence of the direct intergenerational change in children?s IM and showed the potential benefits of using an online mapping application. The IM measures explored in Chapter 3 were further refined in Chapter 4. An innovative mapping application (VERITAS-IM), which captures geospatial IM data, was customised for use in children. The main objective of this study was to compare VERITAS-IM measures with IM Index and IM Licence. Significant linear trends were revealed between IM Index and the VERITAS-derived measures: IM Boundary Area (IMB Area) and Distance (IMB Distance). For every one unit increase in IM Index, IMB Area increased by nearly 4 km2, and IMB Distance increased by 1 km. In regard to parental licences, those who had parental licences in all contexts, except to go out after dark (travel to and from school, cross and cycle main roads, use public transport), had significant higher IMB Area (ranging from 1.46-2.45 km2) and IMB Distance (ranging from 1.68-2.15 km) compared to those who were not permitted these licences (IMB Area: 0.12-0.43 km2 and IMB Distance: 0.57-1.36 km). These results provide the first quantitative evidence that children with greater parental freedoms experience a significant and meaningful increase in their perceived IM area. Historical and current IM in 500 New Zealand children and parents were characterised through IM Index, IM Licence and active travel modes (Chapter 5). Significant generational decreases were observed across all measures. Compared to children today, parents were twice as likely to be granted freedom to travel to school, cross main roads and go out after dark unsupervised. Similarly, parents were four times as likely to be allowed to cycle main roads unsupervised, reflected in an absolute decrease from 76.0%-43.2%. IM Index also declined significantly between parents and children in both males (2.05-1.53) and females (1.77-1.40). A drastic decline in children using active modes of transport was observed, with parents eleven times more likely to use active modes of transportation; only 49.0% of children used active transportation to school and 56.9% from school compared to 91.8% and 93.2% respectively for parents. Overall, each of these measures highlight the significant changes in IM and active transportation in just one generation. To understand the potential impact of declining IM on physical health outcomes, geographically defined VERITAS-IM measures developed in Chapter 4 were compared with objectively measured physical activity and sedentary time (Chapter 6), as well as body composition measures (Chapter 7). Children with high IMB Distance had significantly higher moderate-to-vigorous physical activity (MVPA) compared to those with restricted freedoms (15.4 minutes). Conversely, those with low IMB Area and Distance had significantly higher sedentary time per day than those with high IM (54.5 minutes and 36.1 minutes, respectively). No significant associations were found between children?s IM and body mass index, body fat percentage, or waist-to-height ratio. While the reduction in children?s ability to play and roam independently in the neighbourhood appears to significantly contribute to low levels of activity, it is possible that IM does not mediate the complex causal pathway of childhood obesity in isolation. The development of novel IM measurement techniques, including an innovative online mapping application, provides a unique contribution to IM research. In particular, the VERITAS application offers a standardised measurement technique to quantify children?s independent roaming distances and areas, which is currently absent. Furthermore, the understanding of intergenerational change in children?s IM and novel quantifiable evidence of the relationship between current autonomous roaming, physical activity and obesity in children also represents a substantial original contribution to the body of knowledge in IM. The work presented in this thesis has significant implications for the current measurement practice of children?s IM and it is apparent ongoing work is needed to investigate effective strategies to support children?s independent roaming in the local sphere.