Chapter 1 Introduction
The generation of robust data on children's physical activity levels provides policy makers with accurate data to inform government policies and priorities; for example, the accurate capture of inequality in physical activity, if it exists, in gender and across the socio-economic spectrum. Previous children's physical (in)activity investigations using data from Growing up in Scotland ( GUS) have asked the main carer to recall activity levels on the children's behalf. At age 6, there was no clear social inequality in the patterning of children's physical activity.
However, it is possible that this was due to the type of methodology used to collect the data ( i.e. using the memory recall of the main carer). This report is an exploration of objectively measured and self-reported physical activity and sedentary levels in Scottish 10-11 year old children. Its primary purpose is to report baseline physical activity levels from children involved in GUS. We present these activity levels using two differing approaches: self- reported, and objectively measured ( i.e. using activity monitors) physical activity. Importantly, a key objective of this report was to explore the socio-economic and gender patterning of activity as measured by each methodological approach as a means to inform future methods and policy. The analyses presented within the report form part of a wider academic study exploring the environmental determinants of physical activity in young people that also incorporates GPS data on where young people are most active  .
1.1 Research questions
1. What are the objectively measured physical activity and sedentary levels of Scottish 10-11 year old children?
2. What proportion of Scottish 10-11 year old children meet the current nationally recognised physical activity guidelines of accumulating at least 60 minutes of moderate to vigorous ( MVPA) per day when objectively measured?
3. Do differences in physical activity/sedentary levels and proportion of children meeting the guidelines exist by gender and area level deprivation?
4. Do gender or socio-economic physical activity patterns differ by whether self-reported or objective methods are used to assess physical activity?
Physical inactivity is the fourth leading cause of death worldwide (Kohl et al., 2012). Being inactive is a significant predictor of mortality and morbidity, including cardiovascular disease, type 2 diabetes, obesity, some cancers, poor skeletal health, mental health, and poor quality of life (Hallal et al., 2012). Immediate and future benefits of a physically active lifestyle in children are plentiful and include the strengthening of bones, and the reduction in the incidence of metabolic risk factors such as hypertension and obesity - two strong predictors of the aforementioned conditions and illnesses (Hallal, Victora, Azevedo, & Wells, 2006). There is also an increasing recognition that sedentary behaviour has a significant influence on cardiometabolic risk in children, independent of total physical activity (Vaisto et al., 2014). The concern over sedentariness is amplified as sedentary time in childhood has been shown to track into adulthood (Biddle, Pearson, Ross, & Braithwaite, 2010; Magnussen et al., 2010).
1.2.1 Policy Context
Physical activity has been supported at national policy level for a number of years ( HEBS, 1997) but with a growing body of evidence pointing to the health risks associated with physical inactivity and the benefits of being active for people of all ages, there has been an increased focus by the Scottish Government, building particularly on the success of the Commonwealth Games in 2014. The Scottish Government is committed to increasing rates of physical activity and through the Active Scotland Outcomes Framework  and Physical Activity Implementation Plan  . Scotland is leading the way in its strategic response to the challenge of increasing physical activity and reducing sedentary behaviour.
The Active Scotland Outcomes Framework sets out Scotland's ambitions for a more active Scotland. Success will rely on the collective efforts of communities, individuals and a wide range of partners in areas such as health and social care, education, environment, transport, communities and sport and active recreation. The outcomes will be achieved through the delivery of the Physical Activity Implementation Plan, which adapts key elements of the 2010 gold standard advocacy tool, the Toronto Charter for Physical Activity (Bull et al., 2010), to Scotland. Oversight of the Active Scotland Outcomes Framework sits with the National Strategic Group for Sport and Physical Activity ( NSG), chaired by the Minister for Public Health and Sport. The Active Schools Network and the National Walking Strategy ('Let's Get Scotland Walking', 2014) highlight some of the cross theme work that is being conducted in Scotland.
A range of indicators track progress on the Active Scotland Outcomes Framework, using data from the Scottish Health Survey ( SHeS) and other sources. The importance of physical activity is also recognised through the National Performance Framework  , where National Indicators are used to monitor the Government's progress towards sixteen designated National Outcomes. One of the National Indicators is to 'increase physical activity'. Physical activity is also relevant to a number of other National Performance Framework indicators, such as active travel, educational attainment and mental wellbeing.
1.2.2 Physical Activity Assessment
Physical activity assessment is a challenging undertaking. This is largely because physical activity is a complex behaviour characterised by multiple dimensions and domains: frequency, duration, intensity, and type are all dimensions that can, and arguably should, be measured; leisure time, transportation, in-school, and after-school physical activity are all domains that could be considered important to measure. No one measurement tool exists that can measure all four dimensions of physical activity accurately and reliably (Trost, 2007). Self- report methods are convenient and relatively inexpensive to administer, and are often the most practical and feasible method to use in population surveillance. They have however been subject to criticism: self-reported tools measure perceptions of physical activity rather than physical activity per se and can therefore overestimate levels and prevalence of physical activity (Basterfield et al., 2008); they rely heavily on a respondent's ability to recall activity which may be age-dependent (Baranowski et al., 1984); and the quality of self-reported data is reliant upon the questions asked being matched to the cognitive capabilities of the respondent (Biddle, Gorely, Pearson, & Bull, 2011). The main group of alternative methods to measure physical activity fall under what is considered 'objective measurement' i.e. activity monitors, such as accelerometers, which are small, unobtrusive, and robust battery operated devices that can measure and record movement of the body (or limb). Common places for these to be worn are on the wrist or around the waist. Quite simply, these devices measure and record 'movement' (more precisely, acceleration) and it is this movement that can be translated into useful information such as frequency, intensity, and duration of physical activity. As such, these devices record 'actual' activity, and can provide valid and reliable estimates of physical activity levels in a number of different population groups, including children (Trost, 2007). Although viewed as a promising tool for quantifying physical activity levels in children, this type of method is accompanied by a number of challenges: i) these devices are rarely waterproof and so normally require to be removed before water based activities; and ii) the increased energy expenditure associated with stair ascent, cycling, lifting or carrying objects are often underestimated (a single waist mounted device will not measure upper body activity for instance). However, the contribution of these activities to overall physical activity is assumed to be relatively small ( i.e. hip mounted activity monitors will capture the majority of total body movement) and these devices often produce strong positive correlations with energy expenditure as measured in concurrent validity studies (Freedson, Pober, & Janz, 2005; Trost, 2007).
1.2.3 What is currently known about levels of PA among Scottish children?
Information on physical activity levels in Scotland come from a small number of sources. Primarily, the Scottish Heath Survey ( SHeS) is used to monitor children's activity levels - where parents are interviewed and asked to recall their children's activity - and provides comparable historical data that allows trends to be monitored. The SHeS is the key source of data for the Active Scotland Outcomes Framework, and in 2015, it showed that 73% of all children were sufficiently active to meet the current national physical activity guidelines (Hovald, 2016) as set out by the Chief Medical Officers of the UK - engaging in physical activity of at least moderate intensity for 60 minutes every day (Department of Health, 2011). It also showed that boys were more likely to meet the guidelines than girls (77% v 69%, 2015 data, including school based activity). Activity levels tend to decrease in the adolescent years, particularly among females; data from the 2014 SHeS showed that 82% of children aged 5-7 and 8-10 met the physical activity guideline of 60 minutes, and by age 13-15 this had dropped to 63%. The reduction was most pronounced between the ages of 11-12 (77%) and 13-15 (63%), particularly for girls (a drop from 73% to 53%; including school activity 2014 data; (Gill, 2015). Taking the period from 1998 to 2014, the SHeS has found little significant differences between area level deprivation categories and the proportion of children meeting the physical activity guidelines, although there have been increases in physical activity levels since 2008 that vary significantly by area deprivation, with the greatest increases seen among children living in the middle (third most deprived) quintile (Gill, 2015).
Other data sources exist but are limited to specific age groups, e.g. the Health Behaviour in School-aged Children Survey ( HBSC) (11, 13, and 15 year olds)  , and the Millennium Cohort Study ( MCS; ages 7 and soon to be 14 years old)  Self-reported data from the HBSC study shows an age related decline in physical activity (from 11 through to 15 years old), in addition to a gender gap at age 11 (29% of boys and 21% of girls meet the guidelines of at least 60 minutes of moderate to vigorous physical activity ( MVPA) per day). HBSC also indicated the existence of socio-economic inequalities where boys and girls from more affluent families were more likely to achieve 60 minutes of MVPA. The MCS is one of the few studies that has objectively measured physical activity (accelerometry) in a representative sample of UK children at age 7 (Griffiths et al., 2013). Boys were shown to be more active at this age, both in terms of time spent in MVPA and likelihood of meeting the 60 minute guideline, which was 63.6% vs. 37.8% amongst girls. But no clear socioeconomic differences in physical activity levels were apparent.
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