The effectiveness of school-based physical activity interventions on girls' MVPA, sedentary behaviour and physical activity guideline adherence: A Systematic Review

doi:10.21203/rs.3.rs-3198161/v1

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The effectiveness of school-based physical activity interventions on girls' MVPA, sedentary behaviour and physical activity guideline adherence: A Systematic Review

https://doi.org/10.21203/rs.3.rs-3198161/v1

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Background: Evidence suggests physical activity (PA) levels decline as children age, with levels lower for girls than boys. Consequently, many PA interventions have targeted schools to increase physical activity among children but show varying effects. However, no recent systematic review has assessed their effects specifically on girls’ PA. To address this evidence gap, we conducted a synthesis of studies included in a recent comprehensive Cochrane review of school-based PA interventions, to determine their effect on girls’ PA levels and sedentary time, and proportion of students meeting PA guidelines.

Methods: Studies assessing the effect of school-based PA interventions in students aged 6 to 18 years were considered eligible for inclusion in the original review if they: employed a randomised controlled trial design, targeted school students, and objectively assessed student PA (such as moderate-to-vigorous physical activity (MVPA)), sedentary time, or the proportion of children meeting PA guidelines across the whole day or school day. Studies from the original review were eligible for this secondary analysis if they reported eligible outcomes separately for girls. Where possible, random-effects meta-analyses were undertaken to estimate pooled effect sizes for primary outcomes.

Results: Nineteen of 89 studies from the original review were included. Meta-analysis of 14 studies (11,384 participants) indicated interventions made little to no difference to girls’ minutes of MVPA across the whole day [mean difference: 0.81 minutes/day (95% CI: -0.30, 1.91; I2=50%; low certainty evidence]. Meta-analysis of eight studies (4,811 Participants) found that school-based PA interventions probably decrease girls’ minutes of sedentary behaviour across the whole day [mean difference: -6.73 minutes/day (95% CI: -11.61, -1.85); I2=0% moderate certainty evidence]. One study measured the proportion of students meeting guidelines which found little to no difference [0.65 (95% CI: 0.23, 1.85) very low certainty of evidence] on this outcome.

Conclusions: The positive result for sedentary time but not MVPA suggests that school-based PA interventions are beneficial for improving movement of girls, but not intensity of movement. Future research should focus on improving the design of interventions in an attempt to target their impact on increasing the intensity of girls’ PA levels. Such efforts could include those that target girl specific preferences and barriers.

Physical inactivity is one of the leading risk factors for non-communicable diseases and death worldwide (1). Physical activity (PA) is extremely important for all children aged 5 to 17 years as it has been shown to improve physical, mental and cognitive health outcomes (2). Childhood is a critical developmental period to establish physical activity habits that may track throughout life and prevent or delay the onset of chronic disease (3, 4). There is emerging evidence that this tracking of physical activity from childhood into adulthood is more strongly associated for girls than it is for boys (5).

Given the widely acknowledged benefits of PA in childhood, the World Health Organization (WHO) have developed internationally recognised physical activity guidelines for children and youth aged 5 to 17 years (6–10). The guidelines recommend that children participate in at least an average of 60 minutes of moderate-to-vigorous physical activity (MVPA) per day (2). Evidence suggests that a large majority of children and adolescents are not meeting these guidelines (11). The 2018 Active Healthy Kids Global Alliance physical activity report card, which included self-reported data from 49 countries, estimated that only 27 to 33% of children and youth aged 5 to 17 years met the WHO guidelines of 60 minutes of daily PA (12).

It is also widely acknowledged that girls are less active than boys (13). While there is variation in the estimated differences between boys and girl’s levels of PA (14–16), a large study of European children and youth aged 4 to 18 years indicated that girls perform on average 17% less total daily PA (17). Furthermore, data shows that there is a dramatic decline in PA as children approach adolescence (18–20). For example, the United States 2018 physical activity report card, which used objectively measured data, found only 42.5%, 7.5% and 5.1% of children and adolescents aged 6 to 11 years, 12 to 15 years, and 16 to 19 years, respectively, met PA recommendations (21). The decline applies to PA during the school day, after school and leisure time (22). There is also evidence to suggest that this decline may even occur earlier from age seven (20), with a greater reduction for girls (22).

Schools represent an opportune setting for interventions to improve children’s PA. With the exception of the home environment, children spend more time at school than in any other setting (23). Schools have also been identified as having a considerable influence on children’s PA levels, as they provide opportunities for sport and physical education (PE) participation and have policies regarding PA levels (24–28). Consequently, many school-based PA interventions have been implemented targeting children’s PA levels with varying effects. Several systematic reviews of randomised controlled trials have examined the impact of school-based physical activity interventions on objective measures of MVPA, using meta-analyses. Results of these reviews show that effects are often modest and variable (29–33).

The most recent high-quality systematic review of school-based PA interventions was updated by Neil-Sztramko and colleagues in 2021 (32), and included 89 randomised controlled trials and 96,740 participants. The review examined the effectiveness of school-based interventions on objectively measured physical activity levels of children and adolescents and found minimal impact on child and adolescent MVPA across the whole day with an increase of 0.73 minutes and no effect on sedentary time. Subgroup analysis of these interventions found no significant difference in intervention effects between children and adolescents. No analyses were conducted however, to investigate any differential effects by gender or effects of the interventions specifically for girls. Whereas a 2018 systematic review and meta-analysis of 17 randomized controlled trials, which synthesised objective measures of physical activity in both primary and secondary students showed no evidence of an effect on children’s daily minutes of MVPA and no evidence of differential effectiveness by gender (p = 0.97) (34). Another recent systematic review and meta-analysis of 6,621 children and adolescents aged 4 to 18 years from 20 controlled trials of school physical activity interventions, similarly found a small but significant effect equivalent to 1.45 min/day of additional vigorous physical activity and 1.25 min/day moderate physical activity (35). Effects were reported to be lower for girls and younger students, but the results of subgroup analyses were not reported.

Very few systematic reviews have solely focused on the effects of school-based PA interventions for girls. The most recent of which conducted by Owen and colleagues in 2017 focused on adolescent girls (12 to18 years) reported results from a meta-analysis of 17 studies that school-based physical activity interventions had a small effect on adolescent girls' physical activity levels (36). To our knowledge, there is currently no synthesis that includes the most recent school-based physical activity interventions that have assessed effectiveness on all school age girls (6–18 years). To address this evidence gap, we conducted a synthesis of studies published up to June 2020 included in the most recent Cochrane review update of school-based physical activity interventions (32), to determine the effect on girls’ physical activity levels and sedentary time, and proportion of students meeting PA guidelines.

The review was conducted following recommended methods outlined by the Cochrane handbook (37). This is a secondary analysis of studies included in an existing Cochrane systematic review (32) of the effectiveness of school-based physical activity interventions for all children aged 6 to 18 years including studies published up to 1st June 2020. The review methods were registered prospectively via PROSPERO (CRD42022296549) and are reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for reporting (38).

Search

All studies included in the original review (32) that were identified via the implementation of a comprehensive search strategy were assessed for eligibility. The original review searched following electronic databases MEDLINE, EMBASE, PsycINFO, Cinahl, SportDiscus, BIOSIS, Sociological Abstracts and Cochrane Central Register of Controlled Trials (CENTRAL), using terms related to the condition (physical activity), context (school), population (school-aged children) and study design as were the reference lists of included studies. All included studies and their associated records identified in the original review were screened as per the updated eligibility criteria for this review (see below). Additional searches were also conducted to identify any other potentially eligible associated records for each study that may have reported results separately by gender. The authors of all studies included in the previous review were contacted via email to obtain any associated publications and unpublished data, including data reported separately for girls.

Eligibility criteria: Studies assessing the effects of school-based physical activity interventions in students aged 6 to 18 years were considered eligible for inclusion in the original review if they: employed a randomised controlled trial design, focused on the general population of school students, and included a measure of physical activity (including MVPA, sedentary time or the proportion of children meeting physical activity guidelines) measured via accelerometers or pedometers across the whole day or school day. All included studies from the original review were considered eligible for this secondary analysis (32) and were screened against the updated criteria for participants and outcome (described below).

Participant/population

The original review included studies in children aged 6 to 18 years who attended school, irrespective of their health status, gender or weight status. Studies were excluded if participants received a physical activity intervention as part of a treatment regimen for a specific illness or comorbidity. For this secondary analysis, only studies that reported intervention effects separately for female school students aged 6 to 18 years were eligible (32).

Interventions/exposures

The original review included any school-based physical activity intervention aimed at increasing physical activity and/or fitness in children and adolescents. School-based physical activity interventions included educational, counselling, health promotion or management strategies that focused on promoting physical activity and/or fitness. A range of interventions were included, such as a change to the school curriculum, teacher training regarding physical activity within the school curriculum, and educational materials for teachers, parents, and students. The primary focus for the interventions needed to target the school setting. Included studies also needed to be capable of being implemented by staff in local public health units or community settings, rather than physician or clinic based (32).

Comparator/control

Eligible comparison groups in the original review was no intervention, usual care, or another type of intervention which had to be the same in both intervention and comparator groups to establish fair comparisons.

Outcomes: To be eligible for the original review (32), studies had to report one or more of the following primary outcomes, presented as post-intervention measurement and standard deviation or confidence intervals, or as a change from baseline with standard deviations or confidence intervals: 1) MVPA, assessed via accelerometers or pedometers during school time or whole day or both or 2) Sedentary time, measured as time spent sedentary in total minutes or hours per day or per week, measured via accelerometers or pedometers. 3) Proportion of students meeting physical activity guidelines as reported or calculated by dividing the number of students engaged in 60min/day of MVPA by the total number of students allocated to either the intervention group or the control group. For this secondary analysis, only studies that report these outcomes separately for girls were eligible. Secondary outcomes included any adverse effects reported for girls.

Study selection process

Two review authors (NM and BM) independently assessed the eligibility of all full-text articles included in the original review against these eligibility criteria for this secondary data analysis. A third review author (AH) resolved any discrepancies.

Data extraction and management

The pre-piloted data extraction form used in the Cochrane review was adapted in this current review. Data extraction occurred independently by pairs of review authors (AS, BM, ERG, CG), with a fifth review author (NM) resolving any discrepancies. Information regarding study characteristics (design, participants, interventions, outcomes) from included studies were extracted from the original review, supplemented by additional information that was extracted specifically for female participants, including sample, outcome data and information to assess the risk of bias.

Data analysis and synthesis

Where possible random-effects meta-analyses were undertaken to estimate a pooled effect size for the primary outcomes (minutes of MVPA across the whole/school day, minutes of sedentary time across the whole/school day, and percent meeting PA guidelines). As all measurements were reported in consistent units (i.e., minutes of physical activity), the pooled mean difference for MVPA and sedentary behaviour was calculated using the inverse variance method. For outcomes where too few studies (2 or less) were included to enable meta-analysis, estimates were summarised separately by individual study. Between-group differences at follow-up were prioritised for synthesis as the main effect of interest, however change from baseline was included if between-group differences at follow-up were not reported. As we included only randomised trials and standardised effect sizes were not calculated, it was appropriate to pool both follow-up and change scores (39). Both cluster and individual level randomised trials were pooled in the analysis. We applied a design effect to the standard errors as recommended in the Cochrane Handbook for cluster-level trials that did not appropriately adjust for clustering in their analysis. Where the intra-class correlation coefficient (ICC) for the design effect could not be obtained from the original study (i.e., from the sample size calculation or results section), an ICC value of 0.01 was used, consistent with the methods used in the original review (32). For studies that reported multiple intervention arms, where feasible we combined the intervention effect into one composite effect estimate to allow inclusion in meta-analyses, as recommended in the Cochrane Handbook (37) following recommended formula (40, 41).

Subgroup analysis and investigation of heterogeneity: Statistical heterogeneity was explored using I-squared statistics from the random effects meta-analysis. Heterogeneity was also explored in two pre-specified sub-groups: 1) age – primary (children aged 6 to 12 years) and secondary (aged 12 to 18 years), as physical activity levels are shown to decline as children age, particularly in girls (42); and 2) intervention type (classified according to original review, a) Multi-component whole-school interventions that included a range of whole-school strategies, such as changes to the school environment or curriculum. b) Interventions focused on general school time physical activity promotion, providing opportunities to increase physical activity within school time, such as active academic lessons. c) Interventions that looked at enhancing PE whereby the frequency, duration, or intensity of regular PE classes was increased. d) Other interventions provided opportunities for increasing physical activity during before or after school activities, such as walking or dance groups). As the original review found some differences by intervention type (32), we explored whether such differences persist for female students alone. Sub-group analyses were only undertaken if there was a minimum of two studies per sub-group. Differences in effect estimates across sub-groups were explored using statistical comparisons based on the Q-test.

Missing data

Where possible missing data were estimated using other data reported in the original study (e.g., 95% CIs used to estimate missing standard deviations).

Risk of Bias: Consistent with the original review, we used the Cochrane risk of bias tool version 1.0 (RoB 1) to determine the quality of each study. Risk of bias assessments reported in the initial systematic review for the following categories were extracted and reported: sequence generation, allocation sequence concealment, blinding of participants and personnel and other biases. The following outcome-specific domains were re-assessed for this secondary data analysis based on extracted outcomes: blinding of outcome assessment, incomplete outcome data, and selective outcome reporting. Two review authors (NM & ERG) independently assessed the risks of bias in the included trials and summarised them in tabular form, for one study where NM was involved two review authors not involved (ERG and AS) conducted the RoB assessment. A third review author (AH) was consulted to resolve any discrepancies between review authors. Single studies were defined as having a low risk of bias when all but one domain was assessed at low risk of bias or two domains if one was “blinding of participants and personnel” due to the difficulty in doing this well in school-based physical activity interventions. Single studies were defined as being at high risk of bias when at least three domains were assessed as having an unclear or high risk of bias, or four domains when one was “blinding of participants and personnel.” (32)

Sensitivity analysis

Robustness of estimated results were assessed via sensitivity analyses by removing studies classified as high risk of bias.

Quality Assessment of the evidence

The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach was used to assess the overall certainty of evidence for each primary outcome measure. GRADE takes into account issues related to both internal and external validity to state how confident we are in the effect estimates presented. Two review authors (NM and AH) independently rated the certainty of evidence for each outcome, including the RoB, inconsistency, indirectness, imprecision, and publication bias. Differences were resolved by discussion and checked by a third review author (RKH). For each outcome, we rated evidence certainty as very low, low, moderate, or high based on the GRADE domains as described in the Cochrane Handbook (43). All studies started at a high level of certainty, as they were randomised controlled trials (RCT’s) and were then downgraded based on the five GRADE domains.

Selection of studies

The title and abstracts of 305 records (89 from original review and 216 associated records from previously included studies) were screened for eligibility, of which 170 were excluded. Of the remaining 135 studies screened at the full text, 53 were excluded as they did not meet the eligibility criteria. The main reasons for exclusion were that the paper focused on different outcomes other than the primary outcomes eligible for this review (n = 26), or the paper did not report outcomes separately for girls (n = 27) (see Fig. 1). A total of 19 studies examining the effect of school physical activity interventions on girls' physical activity levels were included in this review.

Characteristics of studies – Participants

A detailed description of the characteristics of the included studies is provided in Additional Table 1 of the supplementary material. All included studies were cluster randomised controlled trials conducted in the United Kingdom (n = 4), Australia (n = 4), United States of America (n = 3), Norway (n = 2), Ireland (n = 2) and one from each Belgium, Netherlands, Iceland and Canada. The number of schools participating in the studies ranged from 3 to 37. The number of girls participating in the study at baseline ranged from 77 to 1,519. Nine were conducted on children aged 6 to 12 years, and ten were focused on adolescents aged 12 to 18 years. Six studies only included girls, whereas the remaining 13 included both boys and girls. Follow-up data collection ranged from 4 to 44 months, with an average of 15 months.

Interventions used

The interventions within included studies were delivered either during the school day or immediately after school. Some studies (n = 3) included additional intervention components delivered in the home, community or online. Most studies employed multi-component whole-school interventions (n = 11) and included a range of whole-school strategies, such as changes to the school environment or curriculum. Other interventions focused on general school time physical activity promotion, providing opportunities to increase physical activity within school time (n = 3), such as active academic lessons. Other interventions looked at enhancing PE (n = 2) whereby the frequency, duration, or intensity of regular PE classes were increased. Lastly, other interventions provided opportunities for increasing physical activity during before or after school activities (n = 3), such as walking or dance groups. While all studies focused on increasing students’ physical activity behaviours, five also targeted other health behaviours such as nutrition or screen time.

Comparators used

Across the 19 trials, 15 compared an intervention to normal school activities, which included regular physical activity or PE. Four studies did not describe what was provided to the control group.

Risk of Bias

The risk of bias ratings for each study is described in Fig. 2. Blinding of schools and participants was the domain with the highest risk of bias, with 13 studies rated as high risk of bias, five as unclear, and one as low. The domains with the lowest risk of bias were baseline imbalances and incorrect analysis. Overall, 16 studies were rated as either high or unclear risk of bias based on the criteria, leaving 3 studies rated as overall low risk of bias. A detailed description of these ratings can be found in Additional Table 2 of the supplementary material.

Effect of the intervention

Impact of school-based interventions on girls’ MVPA

All 19 included studies reported an objective measure of physical activity using accelerometers (n = 17) or pedometers (n = 2). Fourteen studies measured MVPA, 13 across the whole day, and one across the school day. Meta-analysis was possible with 14 studies that reported daily minutes of MVPA across the whole day (11,384 participants) (Fig. 3) and found school-based physical activity interventions may result in little to no difference in the minutes of girls’ MVPA across the whole day [mean difference: 0.81 minutes/day (95% CI: -0.30, 1.91, p = 0.151; I2 = 50%; Low certainty evidence]. Results from the sensitivity analysis whereby studies at high risk of bias were removed had similar results [mean difference: 0.22 (95% CI: -0.95, 1.39); p = 0.7141].

Five studies could not be synthesised in the meta-analysis because they reported MVPA differently. Two studies reported on girl’s school day MVPA separately for moderate and vigorous activity; the first study by Carlin et al, (44) showed an increase in girls' moderate physical activity of 2.04 minutes/day (95% CI 0.52, 3.57; p = 0.122) and a decrease in vigorous physical activity of -1.15 minutes/day (95% CI -2.03, -0.26; p = 0.071). The other study by Salmon et al, (45) showed an increase in girls moderate physical activity from baseline to 12-month follow-up across the three intervention groups (behavioural modification (BM) 11.1 minutes/day (95% CI: 3.8, 18.4); fundamental movement skills (FMS) 10.2 minutes/day (95% CI: -4.7, 25.1) and BM/FMS 0.3 minutes/day (95% CI: -7.7, 8.3)). A study by Ten Hoor et al, (46) reported physical activity as a percentage of time. A difference of 0.4% was found for MVPA (p = 0.046), which translates to approximately six minutes per day. Two studies reported physical activity by steps/day (47, 48), with both reporting no evidence of an effect on step count for the intervention group.

The test for subgroup differences by age found a significant differential effect (p = 0.0297). The magnitude of the effect estimate was slightly larger for older girls (1.66 mins, 95% CI: -0.05, 3.38), compared to younger girls (-0.73 minutes, 95% CI: -2.04, 0.58) (Fig. 4). Sub-group analysis by intervention type was not undertaken due to insufficient studies per category.

Impact of school-based interventions on girls’ sedentary behaviour

Eight studies (n = 4,811 participants) measured girls' whole-day sedentary behaviour using accelerometers, all of which were able to be pooled in the meta-analysis. The meta-analysis found that school-based physical activity interventions probably reduce girls’ sedentary behaviour [mean difference: -6.73 minutes/day (95% CI: -11.61, -1.85); I2 = 0% moderate certainty evidence] (Fig. 5). Sensitivity analysis was not conducted for this outcome due to the small number of studies remaining once those classified as high risk of bias were removed (n = 2), which would not allow for an accurate estimate of the between study variability for the random effects meta-analysis. Tests for subgroup differences by age did not find a significant differential effect (p = 0.79). A sub-group analysis by intervention type was not undertaken due to the insufficient number of studies per category.

Impact of school-based interventions on percentage of girls meeting physical activity guidelines

Only one study reported the percentage of girls who met physical activity guidelines (Harrington, 2018). This study found school-based physical activity interventions may result in little to no difference in the proportion of girls meeting the recommended guidelines of 60 min per day [0.65 (0.23 to 1.85); very low certainty of evidence] (see Table 1).

Adverse effects

Adverse effects were not reported in any of the 19 included studies.

Table 1

Summary of Findings
	Studies	Participants	MD or OR (95% CI)*	I²	Test of subgroup	GRADE quality of evidence
MVPA per day (whole day?)	14	11,551 girls	0.81 [-0.30; 1.91]	50%	NA	Low^a
Subgroup: primary school	7	2877 girls	0.73 [-2.04; 0.58]	2%	Q = 4.73, p = 0.0297
Subgroup: secondary school	7	8674 girls	1.66 [-0.05; 3.38]	68%	Q = 4.73, p = 0.0297
Sedentary per day (whole day)	8	8315 girls	-6.73 [-11.61; -1.85]	0%	NA	Moderate^b
Subgroup: primary school	4	6081 girls	-6.25[-12.24; -0.26]	0%	Q = 0.07, p = 0.7883
Subgroup: secondary school	4	1863 girls	-7.67 [-16.09; 0.75]	0%	Q = 0.07, p = 0.7883
Proportion meeting guidelines	1	1752 girls	0.65 [0.23–1.85]	NA	NA	Low^c
a) Downgraded two levels, one for risk of bias due to high amount of studies having high or unclear risk of bias and one for inconsistency due to the I-squared indicating substantial statistical heterogeneity. b) Downgraded one level due for risk of bias due to a high amount of studies having high or unclear risk of bias c) Downgraded three levels, one for risk of bias due to high amount of studies having high or unclear risk of bias, one level for Imprecision due to the small sample size and due to the estimate covering null effects as well as possible effects of benefit; and one level for indirectness due to only including older schools students aged 12–18 years which was only a specific sub sample of our target population which was all students aged 5–18 years.

The objective of this review was to examine the effect of school-based physical activity interventions on girls' MVPA, sedentary behaviour, and the percentage that meet physical activity guidelines. A meta-analysis of 14 studies suggested that school interventions result in little to no difference in girls' MVPA levels across the whole day. However, meta-analysis of eight studies suggested such interventions probably reduce girls’ sedentary behaviour by almost seven minutes per day. Sub-group analyses of MVPA revealed a differential effect by age group, with a larger effect size for girls aged 12 to 18 years than girls aged 6 to 12 years. No differential effect by age-group was observed in girls’ sedentary behaviour.

Consistent with the previous Cochrane review findings which pooled data for both boys and girls, we found little to no intervention effect on girls’ MVPA levels across the whole day. While the subgroup analysis by age group suggested a higher effect of school-based physical activity interventions on adolescent girls MVPA compared to younger girls, the difference in effect sizes was small and likely not clinically relevant, and thus warrants further investigation with a larger number of studies to confirm. The lack of evidence of an effect in increasing MVPA in girls is consistent with other recent systematic reviews that have found little to no evidence of an effect for increasing MVPA in boys and girls together (34, 36, 49, 50). For example, a systematic review including 17 studies showed no evidence of an effect of physical activity interventions on boys and girls MVPA combined. The same review investigated effects separately by gender and reported no effect for either boys or girls (34).

Encouragingly our review found moderate certainty evidence that school-based physical activity interventions likely reduce girls’ sedentary time by almost 7 minutes, with no differential impact by age. The effect observed here is larger and the evidence a higher degree of certainty than the original review, which reported a pooled effect of low certainty evidence of 3.78 min/day (95% -7.80, 0.24). This is an encouraging finding given even marginal reductions physical inactivity can substantially reduce the attributed burden of disease of this modifiable risk factor (51–53).

Given the positive impact of school-based interventions on girl’s sedentary behaviour, future studies should explore how we can extend this positive change to improve MVPA levels as well as identify why interventions are not increasing girls PA. To ensure population wide benefits can be achieved for girls, future school based PA interventions should be based on strategies that are matched to preferences for girls, address commonly identified barriers to girls involvement in PA, and are easy to implement and scalable. Some suggested strategies that may be worthy of further investigation are discussed here. These strategies are suggested based on the current evidence as being either scalable or easy to implement and address some of the common barriers of girls participating in physical activity. Short active classroom breaks or energisers, could be a simple strategy to address all student activity levels, including girls. Only one of the included studies specifically included active breaks in their intervention (54). Multiple implementation trials have illustrated that classroom energisers are an effective strategy for increasing the minutes of scheduled physical activity opportunities that students have throughout the day (55, 56). Similarly, systematic review evidence of activity breaks on student’s physical activity levels has illustrated their positive effect in increasing student participation in moderate to vigorous PA (57).

Another simple, scalable strategy that could help improve girl’s participation in PA by addressing a common barrier, is considering the use of activity enabling uniforms, such as a sport uniform, to be worn every day at school. None of the included studies included changing to activity enabling uniforms in their intervention design. However, the use of formal uniforms that include tunics and leather shoes have been identified as a barrier to students, especially girls to taking part in school PA (58). Allowing students to wear their sports uniform everyday has been found to be an acceptable and feasible strategy to addressing student physical activity (59, 60), one that is worthy of assessing the impact on girls PA (61, 62). Finally, girls should be extensively involved in the design and development of any interventions that are targeting girls PA (34). None of the included studies included Co-design as part of the intervention, Incorporating girls in the development of future school-based PA interventions will help to increase engagement and acceptability (63). Even modest improvements in students’ physical activity, especially vigorous activity, could have important health impacts at a population level. Therefore, identifying effective school-based physical activity interventions that are suitable for large-scale implementation should be a priority (64).

While only one study reported the impact of school-based physical activity interventions on the proportion of girls meeting physical activity guidelines (65), that study was consistent with the overall results in the original review, which similarly showed little to no difference for this outcome. These findings are also consistent with previous literature that children are not meeting recommended guidelines (66). More studies that test the impact of school-based PA interventions on student compliance with guidelines are needed in order to determine if school-based physical activity interventions can increase the number of children that meet the WHO guidelines. Given the importance that the World Health Organisation place on meeting these guidelines it would be beneficial to know if the physical activity interventions being implemented do in fact contribute to meeting this outcome.

The results from this review need to be interpreted in the context of the certainty of the evidence. Evidence ratings for all three outcomes were downgraded one level for high or unclear risk of bias indicating that higher quality RCTs free of bias are required to increase our confidence in the findings. We are aware that sometimes this may be difficult, for example blinding of participants was often rated as high, however it is recognised that it is not always possible to do so in school-based studies. In terms of the breadth of evidence identified, of the 89 studies in the original review, only 19 reported data separately for girls, and of these, only six interventions were designed specifically for girls. This highlights a need for future research to assess the impact of school-based PA interventions universally delivered to both genders to determine whether they are effective for girls. Only one study reported percent of girls meeting physical activity guidelines (65). This makes it difficult to draw conclusions on the effectiveness of physical activity interventions having an effect on this outcome highlighting the imprecision of the estimate that school-based PA interventions have on girls meeting the guidelines. There was also a large amount of attrition for accelerometer data which often included large amounts of participant data being excluded from analysis due to not meeting wear time criteria. Methods are currently being explored for measuring intensity levels which include more of the data which may address this issue in future studies (67)

Strengths and limitations

A strength of this secondary analysis is that the protocol was prospectively registered with PROSPERO, ensuring all methods were considered and decided upon prior to undertaking the review, thus reducing introducing any bias based on the results obtained. It also restricted studies to those using objective measures of physical activity, the preferred method of measuring physical activity levels as it results in less reporting bias as well as reducing social desirability and memory/recall issues associated with self-report methods. Additionally, the secondary analysis nature of the review ensured that we could assess the impact of school-based interventions on girls physical activity in a timely and resource conscious manner (68). The review also included the details of the interventions for each of the studies, which helps to characterise the types of intervention strategies that may be contributing to reducing sedentary time. Finally, this review only considered studies included in an existing high quality Cochrane review of RCT’s which ensures high quality evidence. A limitation of this review was that we did not conduct an independent search that may have picked up further or more recently published studies. Additionally, our results and conclusions are based on the small proportion of school-based PA studies that have reported separate results for girls to date despite most of the studies included in the Cochrane update included girls. Lastly, although studies were undertaken in schools from diverse geographical regions (i.e., urban and rural), with populations of varying SES and race/ethnicity, they were predominantly conducted in higher income countries; therefore, the extent to which these findings are generalisable to middle or low income countries is limited. Future research is required to address or develop new interventions that meet the needs of different context, such as lower income countries.

Evidence from randomised controlled trials of school-based physical activity interventions synthesised in this review suggests that such interventions may not increase girls MVPA, but likely decrease girl’s sedentary behaviour. Future research should focus on improving the design of interventions in an attempt to target their impact on increasing the intensity of girls’ physical activity levels, assessing the impact of universally implemented school-based physical activity interventions on girl’s physical activity levels, as well as looking to co-develop school-based PA interventions with girls on the basis of their preferences and addressing barriers to their participation in physical activity while at school.

PA: Physical Activity

MVPA: Moderate Vigorous Physical Activity

VPA: Vigorous Physical Activity

MPA: Moderate Physical Activity

GRADE: The Grading of Recommendations, Assessment, Development and Evaluations

RoB: Risk of Bias

SMD: Standardised Mean Difference

CI: Confidence Interval

RCT: Randomised Controlled Trial

PE: Physical Education

Ethics approval and consent to participate: N/A

Consent for publication: N/A

Availability of data and material: The datasets during and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests: The authors declare that they have no competing interests

Funding: RKH is supported by NHMRC Early Career Fellowship (APP1160419). NN is supported by a Medical Research Future Fund (MRFF) Investigator Grant (GS2000053). RS is supported by a National Health and Medical Research Council (NHMRC) Translating Research into Practice fellowship (no. APP1150661).

Authors' contributions: NM led the planning of the review and conducted the screening, data extraction, Risk of Bias, GRADE and drafting the manuscript. ERG contributed to data extraction, and RoB. AH conducted the data analysis, screening and GRADE. AS and CG contributed to data extraction. AH, RS, RKH, NN, and LC contributed to the conception and planning prospective registration of the review, advised throughout the review process, and contributed to and commented on the manuscript. The authors read and approved the final manuscript.

Acknowledgements: N/A

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No competing interests reported.

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The effectiveness of school-based physical activity interventions on girls' MVPA, sedentary behaviour and physical activity guideline adherence: A Systematic Review

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Abstract

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BACKGROUND

METHODS

RESULTS

Selection of studies

Interventions used

Comparators used

Risk of Bias

Effect of the intervention

Impact of school-based interventions on girls’ MVPA

Impact of school-based interventions on girls’ sedentary behaviour

Impact of school-based interventions on percentage of girls meeting physical activity guidelines

Adverse effects

DISCUSSION

Strengths and limitations

CONCLUSION

Abbreviations

Declarations

References

Additional Declarations

Supplementary Files

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