1. Introduction
Physical activity (PA) is associated with numerous health benefits in school-aged children [
1]. Beneficial effects relate to cardiovascular [
2] and cardiometabolic risk factors [
3], and mental health [
4]. Internationally it is recommended that children engage in moderate-to-vigorous PA (MVPA) every day for at least 60 min [
5,
6,
7]. Report cards on the overall PA of children and youth across 38 countries using self-reported data from a number of surveys have specified that levels are low [
8]. Grades of D- were given to England, Australia, Canada and USA, indicating that less than 30% of children in these countries are sufficiently active [
8]. Moreover, data from the International Children′s Accelerometry Database (ICAD) [
9] reveal that children aged 4–18 years engage in MVPA for an average of 30 min per day [
10], and that after the age of 5 years there is an average decrease of 4.2% in total PA with each additional year of age, due to lower levels of light-intensity PA (LPA) and also a progressive increase in the volume of sedentary time (ST) [
9]. Excessive time spent sedentary is positively associated with markers of adiposity and cardiometabolic risk [
11]. International PA guidelines make further recommendations in regards to limiting the amount of ST children accrue [
5,
6,
12]. Current evidence suggests that screen time has a bigger impact on health compared with overall ST [
13]. For example, television viewing has been shown to demonstrate a strong relationship with overweight/obesity and inverse relationships with fitness [
14]. High levels of time engaging in screen-based ST have also been linked to lower self-esteem in youth [
15].
This evidence linking low PA and high ST to adverse health outcomes warrants interventions which promote PA participation and ST reduction in children. Within the school setting there are PA opportunities during discretionary periods between lessons and at break times/recess, through classroom activities, during structured PA periods such as physical education (PE) lessons, and through extra-curricular opportunities before and after the formal school day [
16]. Investigations have indicated that PA during school recess can contribute towards up to 40% of a child′s recommended daily PA [
17], whilst PE has been shown to play a substantial role in providing PA for children as they are more active on days with PE than without [
18]. Thus, schools have been identified as a key environment for child PA promotion. Over 95% of youth and therefore the full socio-economic spectrum of the paediatric population can be reached and engaged regardless of individual circumstances [
19,
20,
21]. Lower socioeconomic status (SES) home environments typically provide more opportunities for ST and fewer for PA [
22]. It has been argued that more positive attitudes towards the value of PA and healthy lifestyles are evident in families with a higher SES, which may be reflected by high SES children attaching greater importance to PA participation for health benefits, relative to perceptions from a comparable group of low SES children [
23]. This trend was observed by Drenowatz et al. [
24], through the use of household income as an indicator of SES, and steps per day to assess free-living PA, with lower PA levels and more time in sedentary behaviours found among low SES children. However, use of different methods of measuring PA and SES suggest that associations reported between SES and children′s PA are equivocal [
25]. School environments provide the opportunity for SES influence to be minimised due to all children attending regardless of individual circumstances. In order to develop effective PA interventions within schools it is important to understand all factors which influence participation [
26]. PA and sedentary behaviours are complex and their occurrence varies within different domains. Youth PA and ST correlates are represented at the individual, interpersonal, organisational, and system levels [
27]. In addition to SES, correlates consistently associated with PA in children include sex, age, ethnicity, perceived competence, and perceived barriers [
28]. Whilst it is useful to understand what influences children′s habitual PA and ST, these may not be consistent within specific contexts and environments such as schools [
29] and thus their investigation is warranted.
Schools are identified as important settings for health promotion through PA. In the UK, the Government′s plan for action to reduce childhood obesity has reinforced the importance of school recommending that children should accumulate at least 30 min of MVPA within school every day [
30]. For schools to be active environments and for successful interventions to be implemented, it is important to understand what influences PA-related behaviour during school hours. The aim of this study therefore, was to investigate the child and school-level influences on children′s PA levels and ST during school hours in a sample of English children from a low-income community.
4. Discussion
This study investigated predictors of low-income children’s school environment PA levels and ST. Significant child-level predictors were maturity offset, CRF, weight status, WtHR, ST, and MVPA, while the significant school-level predictors were number of children on roll and playground area. Previous research has reported variables such as sex, SES, and self-efficacy to be predictors of children’s habitual PA [
28]. However, these predictors were not associated with PA or ST during the whole school day or specific segments of the school day in this study. The fact that SES was not a significant predictor was likely due to the homogeneity in the children’s IMD scores. The exploration of children’s time-specific PA has identified age and gender to be consistently associated with school morning break PA [
29]. Significant differences were observed between boys and girls for school day ST and MVPA, for MVPA during morning break and PE, and for lunch break ST, LPA, and MVPA in the current study, but sex was not significantly related to ST or PA in the multilevel analyses. Previous research has shown the effect of sex on PA to reduce or even disappear when maturity status is controlled for [
60,
61]. This research may explain why sex did not predict ST and PA, but maturity offset significantly predicted MVPA during the school day, morning break, and PE. Disengagement from PA aligning with maturation is associated with a variety of behavioural, social and biological factors [
62]. Furthermore, the contribution of biological maturity to variation in PA should consider factors such as activity context [
62]. Our results indicate that children’s maturity status influences MVPA in the school environment, thus it is important to understand how school PA practices and policies recognise this influence to enable all children to engage in MVPA during school hours regardless of their maturity status. Furthermore, the children in this study were largely pre- and early-pubescent. The influence of maturation may be exacerbated in high school environments as PA is known to gradually decline as adolescents progress toward the mature state, i.e., adulthood [
63].
Sedentary time and MVPA were the most consistent predictors across the different periods, with MVPA significantly predicting less ST, and ST levels significantly predicting less MVPA. This is consistent with previous research studying break time periods of the school day, in which an inverse association was reported between sedentary activities and percentage of time engaged in MVPA [
64]. Whilst our analysis found that one behaviour predicted less of another, this does not imply that ST displaces PA and vice versa. Marshall and colleagues [
65] found correlations between sedentary behaviours and PA to be small and positive, suggesting ST does compete with and coexist with PA. However, small increases in MVPA levels within the school environment which help to reduce ST should be advocated due to the known health and development benefits of MVPA and negative health implications of excessive ST in children [
13]. The replacement of sedentary behaviour with PA is also of particular importance for children who are overweight or obese. Weight status was a significant predictor in the current study, with those who were overweight or obese participating in less MVPA during morning break for example. Results from intervention studies suggest that preventing excessive sedentary behaviour may be an effective approach in improving healthy weight among children [
66]. As overweight/obese children have a higher chance of becoming overweight or obese as adults and subsequently being at risk for chronic diseases [
67], advocating reduced ST and increased MVPA in the school setting among this group is important. Additionally, out of school MVPA was a significant inverse predictor of LPA during the school day, morning break and PE, and a significant positive predictor of MVPA during the school day, lunch break and PE. Given that activity during the school day was low overall, it appears that children who accrued more MVPA out of school participated in more during school, regardless of individual schools′ PA provision. Conversely, creating more opportunities for activity during the school day can prompt higher activity levels to be sustained out of school, which lends further support for promoting MVPA participation in the school setting [
68].
A significant predictor of MVPA during PE lessons was PA enjoyment. This reinforces the need for children′s PA experiences to be fun and enjoyable as PA enjoyment is a recognised mediator of behavioural change in PA interventions [
69]. This finding aligns with theories of motivation, in that the participation in activities for joy or pleasure results in a greater adherence due to participants being intrinsically motivated to engage [
70]. Enjoyment is a key principle of the recently proposed ”SAAFE” framework for the design and delivery of organised PA sessions for children and adolescents [
70]. Our findings support this principle in relation to MVPA participation during PE lessons. This is of significance due to the importance of PE within the school environment; research has shown that PE plays a considerable role in providing PA for children with increased activity levels on days in which PE is provided [
18]. Furthermore, PE can develop fitness, gross motor skills and overall health [
16]. PA provision scores obtained by schools also significantly predicted PE MVPA levels. In the context of UK schools there is a need for an objective measure, which captures how schools operate in relation to PA provision, as opposed to the US based tools previously published [
54,
55]. Within UK schools government funding is provided to improve the quality and breadth of PE and sports provision in primary schools worth £150 million per year [
71]. Whilst not exclusively for PE delivery, UK schools have the freedom to determine how best to use this funding to improve curricular and non-curricular PA provision, but are expected to be accountable for measuring the impact of their spending [
71]. Elsewhere, such as in the U.S., school based PA opportunities differ from state to state, district to district and from school to school based on decisions made by state policy makers [
72]. Local policies and the degree to which they are adhered to or enforced there, impacts children’s PA accrual in schools [
54]. Given the differences between school operations in these examples of the UK and U.S., objective tools to measure school based PA provision which are country-specific would be useful to help schools decide on how to use funding or to help policy makers understand what is being done at the level of individual schools. Furthermore, the use of an objective tool would be useful for researchers who wish to implement school-based interventions targeting areas of the school day most in need of intervention. In our analyses, school-level variables had limited associations with ST, LPA, or MVPA. Furthermore, PA provision scores from the audit tool did not explain or capture the differences between schools. Variance of activity levels explained by differences between schools were substantial, suggesting behaviours during periods of the school day varied between the participating schools. For example 54% of morning break and 75% of lunch break ST variance was explained by differences between schools. In comparison, a study examining children’s ST and MVPA during recess found total variance explained by differences between schools to be 12% for ST [
73]. It is unclear why the between-school variance is higher than was reported by Ridgers et al. (2010) [
73], particularly for ST. There are however a range of different factors related to school break times which can vary between individual schools. The current analyses included PA provision, playground space, and number of children, while other studies have shown provision of equipment, climate, and number of permanent play facilities to be associated with PA behaviour [
73,
74]. Thus, differences such as these which are particular to individual schools impact children’s ST and PA, and serve to highlight the need for analyses to account for the contribution of schools to PA outcome variance.
Number of children on roll inconsistently predicted ST and PA, depending on the period. For example, at morning break number on roll predicted more ST and LPA, whilst at lunch break it was associated with more ST and MVPA. A review of the overall PA behaviour of 10–18 year olds found the presence of peers and friends to be associated with PA [
75]. This is to be expected in contexts such as morning break and lunch break, particularly in younger age groups, as peers will always be present. A systematic review of PA during school recess found 48 studies that reported a negative association between number on roll and PA and 38 studies reporting no association [
76]. Given the inconsistencies of the current study and that of previous research, methodologies such as context-specific systematic observations and tools (e.g., SOCARP) [
77] would help to further our understanding of children′s PA-related social dynamics and behaviours.
The subjective nature of the audit tool used and its completion by school staff is a limitation of the current study. A further limitation was the use of timetabled school times to define the segments of break and lunch times and PE. Actual recording of specific school period times during monitor wear by teachers would allow greater certainty that the activity recorded took place in the period of interest. This though would place additional burden on class teachers to record these times on multiple occasions each day. A greater range of school-level predictors may have better explained differences between schools, for example the presence of equipment during break and lunch breaks, fixed equipment and playground markings. The most important limitation is the cross-sectional nature of the research design which prevents conclusions to be made regarding causality. A strength of this study was the use of objectively assessed PA. Furthermore, the use of raw accelerations avoids the uncertainty of pre-processed data such as counts and the possibility that signal filtering methods alter study results [
78,
79]. The use of raw data also gives an increased control over data processing as well as the opportunity to improve comparability and consistency between studies which use different monitors for example [
51]. In addition, the multilevel analyses allowed for the nested nature of children within schools and also school level correlates to be studied.