This study investigated whether characteristics of accelerometry-measured physical activity behaviour across the school week and over the weekend vary according to the amount of independent mobility a child is granted, and, whether the type of neighbourhood in which a child resides in (urban vs. inner-suburban, low vs. high SES) is associated with any observed relationships. We found that over half (61%) of children were offered some sort of independent mobility (i.e., were sometimes, often or always allowed out without adult accompaniment); the likelihood of being granted some independent mobility, however, differed according to the child’s gender and age. Nearly 70% of boys were offered this independent licence, compared to just over half (54%) of girls. Age appeared to be a moderating factor, but only in boys, with older (and in fact taller) boys being granted more independent mobility than younger, shorter boys. These differences in age and height were however relatively small (likely a result of the narrow age range of the sample (10 to 12 years)) and of not enough practical significance to justify controlling for in further analyses. Nevertheless, our findings support previous studies suggesting that age is associated with CIM  and also that gender is a strong correlate, with boys experiencing more independent mobility than girls [39–49].
Children who were granted at least some independent mobility had more positive physical activity profiles across the school week, over the weekend, and during the after-school period. Importantly, all characteristics of physical activity behaviour (total physical activity, and time spent in light and MVPA) were significantly greater, and time spent sedentary significantly lower, in comparison to children whose IM was restricted. Our findings are in line with previous evidence showing positive associations between independent mobility and children’s physical activity [15–18]. Our findings contribute to the CIM and health literature by examining possible associations with other aspects of physical activity behaviour in children (i.e., sedentary behaviour , light intensity activity, total physical activity), particularly during discrete periods of the week (weekdays, after-school period, weekend). The fact that this is the first study to identify associations between CIM and sedentary behaviour and light physical activity in particular is noteworthy, given a) increasing evidence that sedentary behaviour, in comparison to physical activity, has very different, independent, negative effects on human metabolism, physical function and health outcomes [60–68] and, b) increasing priority towards shifting time spent sedentary to time spent in light physical activity (i.e. minimizing sedentary behaviour and maximizing light physical activity) . For example, more recent evidence suggests that health benefits accrue when sedentary time is replaced by light physical activity ; including measures of light physical activity in explorations with health outcomes is now strongly recommended .
While a greater degree of CIM is related to a more optimal physical activity profile in general, gender-specific relationships are apparent. For example, the level of CIM granted to girls impacts all characteristics of PA, with the exception of light PA accumulated across the school week. Like girls, CIM does not appear to have an impact on boys’ accumulation of light PA on weekdays, nor does it seem to impact light PA accumulated over the weekend. Time spent sedentary is also no different between boys granted high or low CIM. Interestingly all characteristics of PA during the after-school period are affected by the level of independent mobility afforded to boys and girls, suggesting that the influence of IM on PA behaviour is particularly salient during this time period. The overall results suggest that CIM-PA relationships are different for boys and girls, with certain aspects of “periodic activity” (i.e., after-school period) impacted more than others. Ultimately, this emphasizes the importance of considering gender and the type of day/period in future examinations of CIM-PA relationships.
When the impact of independent mobility on characteristics of physical activity behaviour is examined across neighbourhood classification, significant interactions emerge. However, similarly, these interactions vary according to gender, and the type of day (weekday, weekend) or period (after-school) being examined. Independent mobility seems to matter more for boys who live in urban neighbourhoods and for girls who live in suburban neighbourhoods. For example, boys offered greater independent mobility in urban neighbourhoods, of both low and high SES, have more positive physical activity profiles (i.e., accumulate more PA and spend less time sedentary) across the week and during the after-school period than boys whose licence is restricted in these neighbourhoods. Alternatively, girls in suburban, low SES neighbourhoods whose independent mobility is not restricted have more positive weekday and after-school physical activity profiles than girls who face restrictions in these neighbourhoods. On the weekend, however, CIM appears to have the strongest relationship with the physical activity patterns of girls in suburban, high SES neighbourhoods (i.e., the difference in weekend PA between girls granted low or high CIM is greatest in this neighbourhood).
The influence of CIM in these neighbourhoods also impacts different aspects of physical activity behaviour. In NL neighbourhoods, CIM seems to have the greatest impact on girls’ accumulation of MVPA across the school week and during the after-school period, whereas in NH neighbourhoods, total physical activity is impacted most on at the weekend. Restricting girls’ independent mobility in OL neighbourhoods seems to be related to more time spent sedentary, and less time in light activity, during the after-school period. For boys, restricting independent mobility in OL neighbourhoods is related to a lower accumulation of MVPA, across the school week and over the weekend, whereas light intensity (and total PA on the weekend) is impacted most in OH neighbourhoods. The after-school period, however, seems to be most affected in these urban neighbourhoods: no CIM is associated with more time spent sedentary and less time in light and MVPA. The after-school period is an opportune time to accumulate physical activity, however, for most Canadian children it remains underutilized. Our results show that children are spending anywhere from 68-75% of the after-school period sedentary (up to an hour and a half of those two hours sedentary), and only 3-6% of that time in MVPA (4 to 7 minutes). A better understanding of barriers towards CIM, particularly during this critical period, is a necessary step towards shifting these proportions.
Strengths and limitations
Strengths of this study include the large sample (n = 856), the sampling methodology (stratification of children according to urban vs. inner-suburban, low vs. high SES neighbourhoods, using home address data) and the use of an objective measure of physical activity to examine numerous characteristics of physical activity behaviour during weekdays, the after-school period, and over the weekend. The investigation of the entire physical activity intensity spectrum (i.e., not only time spent in MVPA during these periods, but also time spent sedentary and in light activity) supports increasing evidence around the importance of assessing time spent sedentary and in light and MVPA, given independent relationships with various health outcomes exist. The collection of high-frequency physical activity data was also appropriate for describing children’s physical activity behaviour . The limitations of this study include the narrow age range of children sampled and the examination of children living in neighbourhoods throughout the city of Toronto, preventing the generalizability of findings to other age groups and locations. Also, there is the possibility of inflated type I error due to multiple statistical comparisons. Finally, micro-level community design and land-use characteristics (e.g. connectivity, access/proximity to recreational facilities, residential density) were not examined in relation to both CIM and PA behaviour; these are a focus of future investigation.