For the 2012 HSE, a sample of 1,732 individual children was included in the present analysis, 50% of whom were female. Table 1 shows mean total and domain-specific MET minutes per week by individual factors for the 2012 HSE. For the 2015 HSE, 5,346 individuals were included in the analysis, of which 49% were female. Table 2 shows mean total and area-specific MET minutes per week by individual factors for the 2015 HSE. Data are presented in separate tables, while mean values and standard deviations are broadly consistent across datasets, incorporating physical activity into school in the HSE 2015 does not make the estimates directly comparable. Comparisons between 2012 and 2015 HSE data show that although occasional differences are observed between isolated subgroups, there are no systematic differences between survey iterations.
effect by gender
For the 2012 HSE, boys overall reported a higher level of physical activity than girls (t1732= 4.86, p< 0.001). There were only minor differences between boys and girls in the totals for active travel and non-specific physical activity, with no specific differences found when stratified by age group. Boys have a higher proportion of physical activity from formal sports than girls (t1674= 5.47, p< 0.001), while girls, conversely, recruited a higher proportion of physical activity from informal activities than boys (t1674= -2.83, p = 0.005), although boys still reported higher absolute levels of informal physical activity (t1730= 3.15, p= 0.005). Stratified by age groups, informal activity differed only significantly between genders within the 13-15 year old group, but formal activity showed large gender differences in all school age groups, with boys consistently having more informal activity and more physical activity overall achieved activity as a girl.
A similar pattern was observed in the 2015 HSE data, with boys reporting significantly higher levels of physical activity than girls in terms of total MET minutes per week, including (t5436= 7.29, p< 0.001) and without (t5436= 7.19, p< 0.001) school physical activity. These differences between boys and girls largely persisted when stratified by age. Again, boys recruited a higher percentage of total physical activity than girls from formal activities (t5122= 10.30, p< 0.001). The remaining domains of active travel, non-specific, informal, and school physical activity showed little difference by gender.
effect by age
Within the 2012 HSE, age predicted outcomes for total MET minutes per week and for all domain-specific physical activity, with gender being accounted for. Overall, age was positively correlated with active travel, nonspecific and formal physical activity, but negatively with full and informal physical activity. Domain-specific contributions from each domain to total MET minutes per week are shown in Fig. 1. Further analyzes were stratified by sex, finding that age is a significant predictor for all domain-specific outcomes. However, while age was a predictor of total MET minutes per week for girls (f4= 6.42, p< 0.001) it was not for boys (f4= 1.19, p= 0.312).
For the HSE 2015 data, age again predicted results of total MET minutes per week, both including and excluding physical activity at school, and predicted all domains of physical activity. Age again positively correlated with total active travel, nonspecific physical activity, formal activity, and school activity scores, and was negatively correlated with informal activities and total MET minutes per week, both including and excluding the contribution of school time. The domain-specific contribution to the total MET minutes per week is shown in Fig. 2. Age remained a predictor for all domains when stratified by sex; However, and while overall activity in girls differed significantly by age (f4= 17.48, p< 0.001), this was not the case for boys (f4= 1.47, p= 0.208).
HSE 2015 included measurement of curriculum-time physical activity, the first time this was included in an HSE iteration. The relative contributions of school activity are shown in Figure 2 stratified by age and sex. There were significant differences in school physical activity levels for both sexes, with age predicting differences in school-based MET minutes per week for both boys (f4= 106.54, p< 0.001) and girls (f4= 101.30, p< 0.001).
Effect by weight status
For the 2012 HSE data, weight status did not predict total MET minutes per week (f2.7= 0.85, p= 0.428) nor a domain-specific sum, nor were there any significant effects when stratifying by gender. At the 2015 HSE, weight status significantly predicted total MET minutes per week, both including (f2.7= 6.04, p= 0.002) and without (f2.7= 6.10, p= 0.002) school activity that girls (f= 4.20, p= 0.015), but not boys (f2.6= 2.19, p= 0.112), when stratified by sex. Increasing weight status also predicted a reduction in informal activity (f2.6= 4.82, p= 0.008). When stratified by gender, girls (f= 5.37, p= 0.005), but not boys (f2.6= 0.91, p= 0.402) maintained a significant effect for informal activity, with no specific effect by gender on formal activity.
effect of withdrawal
Within the HSE 2012, total MET minutes per week did not differ according to QIMD for boys or girls. There was also no significant impact for QIMD across domain-specific total scores, with the exception of formal physical activity, which differed significantly (f4.9= 3.98, p< 0.001), an effect that persisted in girls stratified by sex (f4.8= 4.78, p< 0.001), but not boys (f4.8= 1.24, p= 0.292).
For HSE 2015, total MET minutes per week varied by QIMD category when (f4.9= 2.38, p= 0.049) or without (f4.9= 2.55, p= 0.037) school activity, although both effects failed when stratified by gender. An increase in QIMD was negatively associated with non-specific formal and school activity levels, but positively with levels of informal activity. Stratification by gender showed that the differences persisted in all activity domains, with the exception of active travel and school activities.
Effect by Ethnicity
Within the 2012 HSE, participants from different identified ethnicities showed significant variation in total MET minutes per week (f4.9= 6.02, p< 0.001) when controlling for age and sex. At the domain level, there were no major differences in active travel or non-specific activity levels, but there were implications for formal (f4.9= 5.83, p< 0.001) and informal (f4.9= 4.54, p= 0.001) activity.
For the 2015 HSE, different identified ethnic groups showed significant variation in total MET minutes per week, both when (f4.9= 28.97, p< 0.001) and without (f4.9= 28.12, p< 0.001) school activity when age and sex are controlled for. There were significant effects for all domain-specific total scores that persisted when stratified by sex, with the exception of boys' active travel (f4.8= 0.79, p= 0.533) and school activity (f4.8= 0.59, p= 0.667).
Stratified analysis by level of physical activity
In addition to the above analyzes of the entire survey sample, it is possible to stratify the responses by level of physical activity to provide a more nuanced description of the data and to extend the work of Payne, Townsend . Stratification of the 2012 HSE cohort by physical activity level shows the relative contributions of each physical activity domain to total MET minutes per week for activity-based quintiles of the population. For the 2015 HSE data, all domain-specific contributions showed significant regression effects by physical activity quintile when age and sex were controlled for, effects that persisted when stratified by sex. There were no statistically significant differences between survey years in comparable domains, although there are significant differences in the graphical representation. Percentage contributions to HSE 2012 and HSE 2015 from comparable areas are shown in Figure 3, with additional data specifically covering HSE 2015 school activities shown in Figure 4.