Barriers and Facilitators of Physical Activity Participation in Adolescent Girls: A Systematic Review of Systematic Reviews

Background: Persistent low physical activity (PA) levels among adolescent girls constitute a public health concern that calls for immediate and evidence-based policy action. This systematic review (SR) aimed to summarize evidence from SRs examining the barriers and facilitators of PA participation in adolescent girls. The objectives were to provide a synthesis of the available evidence and identify key areas for fostering gender-responsive action and policy implications. Methods: A comprehensive search of relevant SR and meta-analyses were performed in PubMed and Cochrane Library, until February 2021. Studies were included if they were SRs or meta-analyses, included adolescent girls aged between 10 and 19 years, and described barriers or facilitators of PA. Two independent authors performed the screening of potentially eligible studies and both assessed the methodological quality of included studies using the AMSTAR 2 tool. The barriers and facilitators were synthesized at environmental, interpersonal, and individual levels. Results: A total of eight SRs were included in the qualitative synthesis. The most frequent barriers identified were the lack of support from peers, family, and teachers, and the lack of time. The most reported facilitators were weight loss, and support from peers, family, and teachers. Key areas for action and policy implementation include an inclusive approach to curriculum development to address gender norms; adequate training of professionals so they have a range of skills to ensure inclusion of adolescent girls; environmental changes in and out of schools to stimulate participation, to allow adolescent girls to be active in a safe and attractive environment; multistakeholder support at local, regional, and national level in incorporating a gender-responsive approach toward PA participation. Conclusion: The results highlight a variety of factors that influences the PA participation of adolescent girls. For the attainment of effective policies that increase PA levels in adolescent girls, it is essential to engage several stakeholders at different levels in incorporating a gender-responsive approach toward PA participation. Systematic Review Registration: PROSPERO, identifier: CRD42020204023.


INTRODUCTION
Regular physical activity (PA) has well-known positive effects on the prevention and control of non-communicable diseases, such as cardiovascular diseases, cancer, diabetes, and depression (1)(2)(3)(4), as well as reduced overall mortality and risk of premature death (5). In children and adolescents, adequate PA also provides benefits to cognitive development, motor skills, self-esteem, social integration (6), musculoskeletal health (7) academic achievement (8), and overall well-being (9).
The World Health Organization (WHO) recommends that children and adolescents aged 5-17 years engage in at least an average of 60 min per day of moderate to vigorous-intensity, mostly aerobic, PA across the week (10). According to a recent study on school-attending adolescents, 81.0% of adolescents aged 11-17 years are insufficiently active (not meeting current daily PA recommendations) (11). The 2020 study by Guthold et al. revealed that a higher prevalence of physical inactivity was found amongst girls in almost all countries globally (84.7%, compared with a prevalence of 77.6% for boys), with no significant changes for girls in these trends over the past decade (11).
Persistent low PA levels among adolescent girls constitute a public health concern that calls for immediate and evidencebased policy action. Increasing PA participation among adolescent girls is an important component not just because of the positive effects on health, but also because PA can play a role in economic development, education, peace-building, and trauma relief in different geographical, cultural, and political contexts (12,13). Promoting PA contributes directly to attain many of the 2030 Sustainable Development Goals (SDG), by promoting policy actions that foster peace, tolerance, respect, and the empowerment of women (14).
Several reviews have investigated the factors that influence PA behavior in adolescent girls and highlighted complex influential factors. For example, a review of the effectiveness of school-based PA interventions on adolescent girls discovered only a small effect of these interventions, namely multicomponent interventions, on increasing PA levels due to complex social and cultural norms that play in the structures of school PA programs rendering limited flexibility in accommodating for gender differences (15). Furthermore, a review of qualitative studies on the selfperception of PA of adolescent girls identified perceived gender bias in sports, along with a limited level of competence in abilities, preference in other priorities, and differing social expectations as impediments for PA participation among adolescent girls (16). Despite the sizable evidence providing insights on the influences of PA behavior for this group, challenges continue to exist in implementing gender-responsive PA interventions (17) leaving girls enduring inequalities in access to and experiences with PA (18).
Limited research has been able to explain how policymakers and implementers can effectively cater toward adolescent girls' needs when it comes to increasing PA levels (11,16,19). Common theories used to explain the factors that affect the PA of adolescent girls have used the socioecological model (18,20,21). Bronfenbrenner's ecological model of human development describes factors that influence behavior to be linked to individual, interpersonal, and environmental levels (22). Nonetheless, previous studies lack on how to translate these factors into practice in terms of a gender-responsive approach to PA promotion in adolescent girls.
A more gender-responsive approach to PA promotion has been recommended in important policies and strategies. The United Nations and WHO have called on the Member States to act to increase gender equity in PA and sport participation. For example, Article 10 of the Convention on the Elimination of All Forms of Discrimination against Women calls on countries to ensure women have equal opportunities for participation in sport and PA (23), also contributing to achieving the SDG number five, gender equality (24). The WHO, through the Global Action Plan on Physical Activity 2018-2030 (12), also reinforces and supports gender equality and the empowerment of girls to uphold this fundamental human right, and a necessary foundation for a peaceful, prosperous, and sustainable world (24). Accordingly, actions are necessary to tackle inequalities in PA, as reflected by the Physical Activity Strategy for the WHO European Region 2016-2025 (25), by improving the availability, affordability, and acceptability of PA in some age groups. In particular, early adolescence may be an opportune transitional period to promote the development of healthy behavior and equitable gender norms early in life that can be transformative both immediately and over the life course (26,27).
The gender disparity of PA in adolescents calls for increased efforts at the global, national, and regional levels to reduce inequalities in opportunities for PAs of adolescent girls. Providing a synthesis of the most recent evidence may assist in the development of gender-responsive recommendations, strategies, initiatives, and policies for implementers. Therefore, this systematic review (SR) of systematic reviews (SRs) aims to (i) summarize evidence from SRs examining the barriers and facilitators of PA participation in adolescent girls and (ii) identify key areas for action and policy implementation.

METHODS
An adapted Preferred reporting item for systematic reviews and meta-analysis (PRISMA) reporting method was used to conduct this SRof SRs (28). The PRISMA checklist is available in Supplementary Material 1. The protocol for this review is registered in PROSPERO (reference number CRD42020204023).

Eligibility Criteria
The study eligibility criteria consisted of the type of studies (SRs and/or meta-analysis); type of participants [adolescent girls 10-19 years of age (according to WHO), or in this age range]; type of interventions (any form of PA practice); and type of outcome (barriers and/or facilitators. Studies were excluded according to study type (editorials, comments, case reports, guidelines, conference abstracts, other reviews); studies without measurement of the outcomes of interest, i.e., studies without barriers or facilitators; studies that aim to find correlations between PA and other factors; studies that aim to analyze the effectiveness of PA interventions; populations with specific conditions (e.g., pregnancy); and studies that do not provide separate data for sex or age category.

Information Sources
A comprehensive search for relevant SRs was conducted independently by the first and second author until February 2021 using two electronic databases: PubMed and Cochrane Library.

Search Strategy
The key search terms used in each database were as follows: ("physical activity" OR exercise OR sport * OR "physical education") AND (child * OR adolescent * OR teen * OR youth OR young) AND (female OR girl * OR women) AND ("gender gap" OR "gender differences" OR factor * OR motive * OR barrier * OR facilitator * OR perception * OR support). We limited the search to study type (SRs, meta-analysis, and reviews) and the English language. The complete search strategy for each database can be consulted in Supplementary Material 2. articles were screened by the information from the title and abstract. Second, potentially relevant articles were retrieved for full-text review and their eligibility for the study was determined. Disagreements were resolved through discussion until consensus.

Data Collection Process
Each selected SR was independently evaluated by the two authors to extract information regarding study design, participants, number and type of included studies, outcome measures, the setting of intervention, and barriers and facilitators. If there were discrepancies in data extraction, authors discussed until consensus.

Data Items
Barriers and facilitators were identified and then synthesized in three main levels (individual, interpersonal, and environment) from Bronfenbrenner's ecological model of human development (22). The individual level refers to perceptions and attitudes of the individual; the interpersonal level refers to the relations with factors that have direct contact with the individual in their immediate environment, such as parents, siblings, teachers, and school peers; and the environment level incorporates formal and informal social structures, and cultural norms, which do not themselves contain the individual, but indirectly influence them.

Methodological Quality
Each eligible SR was evaluated regarding its methodological quality by two independent authors, using the 16-item AMSTAR 2 tool (29). Each study was classified according to critical domains that can affect the validity and conclusion of the review. The critical domains considered for this review were: protocol registered before the commencement of the review (item 2); adequacy of the literature search (item 4); justification for excluding individual studies (item 7); risk of bias from individual studies being included in the review (item 9); appropriateness of meta-analytical methods (item 11); consideration of the risk of bias when interpreting the results of the review (item 13); and assessment of the presence and likely impact of publication bias (item 15). The studies were rated as "high-quality" if there were none or there was one non-critical weakness; "moderatequality" if more than one non-critical weakness; "low-quality" if one critical flaw with or without non-critical weaknesses; and "critically low-quality" if more than one critical flaw with or without non-critical weaknesses. Any disagreements in the classification were resolved by discussion.

Study Selection
Out of the 641 references identified in the initial search in electronic databases, the study selection process resulted in the inclusion of a total of eight studies in the qualitative synthesis (Figure 1).

Study Characteristics
The study characteristics included in this review are shown in Table 1. All studies were SRs, ranging from 2006 to 2019, and published in the English language. Concerning the study design of the original studies, the majority provided qualitative designs (16,31,33,35,36). Regarding the participants, the studies included children and adolescents (30,31,34) or adolescents only (16,32,33,35,36) of the female sex (16,32,35) or both sexes (30,31,33,34,36), with ages ranging from 3 to 25 years. All the SRs included school setting, with some reviews also including community (i.e., public spaces like parks) (16,31,32,36), primary care clinic/health centers (16,31,35), and after school hours setting (i.e., organized by school clubs, in or out of the school facilities) (33). Table 2 shows the assessment of methodological quality for each study. All studies were rated with "critically low-quality."

Methodological Quality
The critical domains where studies did not meet the quality requirements more frequently were the registration of the protocol before the commencement of the review (item 2, n = 7) and the consideration of the risk of bias when interpreting the results of the review (item 13, n = 6). In non-critical domains, all the reviews did not report the complete population, intervention, control group, and outcome (PICO) components (item 1, n = 8) and they also did not report the sources of funding of individual studies (item 10, n = 8). The reviewers were in total agreement on the methodological quality assigned to each study.

Environmental
The most commonly mentioned barriers at the environmental level were the costs of activities available (16,32,33,35), and safety concerns of the neighborhood outdoor areas and

References Barriers Facilitators
(obligations to family and friends, school and homework commitments, length of travel to and from school for the ones in rural areas); lack of motivation (persistent failure during PA, lack of motivation by laziness); physical factors (physical discomforts, too out of shape, fatigue after the day and exercise, perceived beauty cost); capacity (lack of competence in setting goals, low self-efficacy or confidence in the ability to seek support given problems with transportation); lack of knowledge (false beliefs about PA, the perception that PA is of little benefit) NR, not reported; PA, physical activity; PE, physical education.
environment (33,35,36). The most commonly mentioned facilitators in the environmental level were the accessibility and availability of recreational centers (16,32,35), the opportunity to explore new activities (31,32,35), the consultation with girls about sports preferences and formats of delivery (32,34), and the role of media have on influencing change in social norms (33,34). The distribution of the barriers and facilitators among the three levels (individual, interpersonal, and environment) is presented in Table 4.

Summary of Main Findings
This SR of SRs summarizes the evidence of eight studies examining the barriers and facilitators of PA in adolescent girls. This synthesis has highlighted that the most frequent PA barriers reported in adolescent girls were found to be the lack of support from peers, family, and teachers, followed by the lack of time; the most identified facilitators reported for the PA of adolescent girls were weight loss/management, and peer, family, and teachers support (16,(31)(32)(33)35). The majority of reported factors of influence hindering and/or supporting PA gathered in this review were mainly located in the individual and interpersonal levels.

Barriers and Facilitators
The socio-ecological model is one approach commonly mentioned as the most suitable method to illustrate complexities of examining the individual, physical, and social environmental factors when explaining PA behavior in general, therefore can be viewed as applicable for illustrating PA behavior of adolescent girls. Although the data were aggregated according to the three main levels, it is essential to note that there is a dynamic crossover of barriers and facilitators, as one facilitator and/or barrier may be linked to another on a different level. For example, limited social support by a coach/teacher may occur due to the limited physical ability/skill of an individual leading to an overall negative experience, as mentioned in one review (35).
Although the barriers and facilitators by level can be seen separately, it is important to acknowledge the interplay and complexity of each and how they affect the participation of adolescent girls in PA overall when targeting within interventions. Further research is needed in terms of appropriate theoretical frameworks that can provide a clearer way to illustrate such complex intertwined factors that influence the PA participation of adolescent girls. This, in turn, can provide improved guidance when designing multicomponent interventions to target multiple influential factors that address these complex factors affecting PA participation of adolescent girls.
Approaches that can transform the role and relationship of harmful gender norms should be an aim of PA promotion (37). Gender norms have been known to play a significant role not only in the diverse exposure levels to the risk factors of non-communicable diseases in men and women but also in the access to and the use of services and resources (37). Gender norms and stereotypes have a specific influence on PA participation by creating societal expectations of what it means to be feminine/masculine that may limit the access to and use of PA opportunities available. For adolescent girls, gender stereotypes are seen as a barrier toward PA participation. With PA opportunities seen as socially appropriate to boys only, a perceived gender dominance occurs, which decreases the value and access to PA opportunities for girls (16,30,33,35,36). Not only do these norms hinder access to opportunities, but they also play a significant role in body image concerns. Although, body image was perceived as a facilitator in this synthesis (30)(31)(32)(33)(34)(35) warrants should be made regarding the potential to negatively reinforce gender stereotypes that could be harmful to the physical and mental health of girls. Additionally, challenges exist in implementing gender-responsive PA interventions aimed at adolescent girls, calling for increased research and mechanisms on how to effectively respond (17).

Individual
Examples of individual barriers common across the reviews were associated with body image perceptions, such as feeling uncomfortable while participating in PA due to the concerns of appearance and discomfort that for example, were linked to the type of clothing worn and/or perceived skill level (16,(31)(32)(33)(34)(35)(36). Consistent with previous research, negative body image and dissatisfaction have been associated with the age of adolescent girls which can contribute to the negative perceptions and experiences around PA participation (18,38). Interventions that can increase the perceived competencies of girls could be considered one way of which to target negative self-ideals such as PA opportunities that focus on individual progression

Promotion of sedentary activities (36)
Consultation with girls about sports preferences and formats of delivery (32,34) Perception that PA is not culturally valued (16,36) Media in the change of social norms (33,34) Social pressure of feminine appearance and behavior (16,35) Opportunity to engage in girls-only activities (16,32) Safety concerns at neighborhood outdoor areas and environment (33,35,36) Safe environment (31) Limited access to sports/programs in the community (clubs, preferred sports) (33,35) Accessibility and availability of recreational centers/clubs/activities (16,32,35) Limited activities choices in rural settings (16) Possibility of choosing/experiment activities and its delivery (31,32,35) Expensive activities (16,32,33,35) Low cost of programs (33) High distance from recreational centers at community (33,35) Geographic proximity (35) Lack of facilities (30,33) School, neighborhood, and home facilities (33) Fewer opportunities than boys (35) Opportunity to engage in mixed-sex activities or in activities traditionally seen as being for men (34) Limited access to sports/programs in school (33) PA opportunities during school time (33) (Continued) Frontiers in Public Health | www.frontiersin.org

Barriers Facilitators
Lack of transports (33) Lack of resources (30,36) Inappropriate teaching practices (36) Curriculum focused on sports perceived as masculine (33) Outdated sports equipment at school (35) Having to wear a uniform in PE classes (31,36) Lack of privacy in changing rooms (36) Biological changes during puberty (16) Life transition periods (33) Weather conditions (36) No appropriate place for PA practice (30) PA, physical activity; PE, physical education. (18). However, self-perception has been considered largely influenced by the interpersonal and greater social contexts of cultural/gender ideals reinforced by family and peer groups (39). Evidence has suggested that mothers' conversation with adolescent girls around positive body image to be one way to foster improved body satisfaction (40), which may also aid in improved experiences with PA participation. Adolescence is often marked as a highly sensitive and complex period of transition from childhood to adulthood (16). Further heightening vulnerabilities, biological changes experienced by adolescent girls during puberty can lead to discomfort while menstruating and combined with a heightened sense of selfconsciousness which may, in fact, discourage participation in this age group (16). Research has suggested early maturing girls to be particularly prone to develop negative body images as they experience contradictions to the cultural ideals placed on them (39). Limited research has explored the role menstruation may play in hindering PA participation of adolescent girls since only one review in this synthesis mentioned menstruation as a barrier (16). Thus, further research should explore mechanisms to combat potential barriers of menstruation around PA participation as this review found limited evidence suggesting such implications.

Interpersonal
Interpersonal facilitators and barriers most commonly reported in this SR were the variety of and/or lack of support providers for PA of adolescent girls (16,(31)(32)(33)(34)(35). Support by peers, family, and teachers was mentioned evenly amongst the included reviews in this synthesis, potentially suggesting that each provider of support may have an equivalent influence on the PA of girls. A qualitative study that attempted to provide mechanisms for social support in PA for adolescents observed that receiving reinforcement and praise for PA, providing opportunities to practice and improve performance, and providing the practical support necessary to participate (equipment/money/transport) were key forms of support (41).
It is important to note that each support provider may play a different role in influencing the participation of girls in different settings. For example, supportive parents were found in this synthesis to play an essential role for adolescent girls by promoting PA time outside of school through means, such as financial support for the activities, transportation to activities, or overall encouragement to participate (16,31,33,34). Similar research has acknowledged the influential support by parents toward PA of adolescent girls, especially young adolescents who may be more reliant on parents' ability to provide access to PA opportunities (i.e., equipment, cost of activity, and transportation) (42,43).
This form of support places a burden on the financial ability and time of parents to provide the necessary access to resources and transportation to PA facilities, which may foster the potential inequalities from socioeconomic classes unable to provide the financial support required for adolescent girls to participate. Such disparities can also be seen within ethnic/minority PA participation of adolescent girls (18,44,45). Other forms of social support may provide a greater influence in PA participation less contingent on the family. For instance, social support by friends discovered in previous research was to be a greater predictor of meeting the daily PA recommendations for those with low access to PA resources (43). Teacher support, especially important in terms of school PA participation, influences adolescent girls from this synthesis mirrors existing research as well. Evidence has suggested that teacher support in the form of providing encouragement, praise, feedback, and enthusiasm directly targeting adolescent girls can provide increased positive dialog and engagement, which has been reportedly inexperienced by this group (41,42).

Environmental
Most of the SRs in this synthesis focused on the school setting PA and reported barriers across all three levels: be it the teachers, social or physical environment, or the activity/curriculum. While numerous efforts have been made in the past decade to increase PA and sport participation of adolescent girls in this setting, many interventions have been found to have only small to limited effects (15). This may be due to the multidimensional barriers that span across the three levels, making it difficult to accurately address existing interventions targeting adolescent girls. Despite this, schools may be an important entry point for improved PA promotion among girls, especially if they are effective in changing the traditional structure of PE that hinders participation. This is consistent with existing literature that has made claims of gender biases in the PE curriculum calling for new ways of developing a more inclusive approach (46).
Considerations should be made to the social and built environment of the setting that offers PA in schools to be appropriate to gender preferences and needs. For instance, this synthesis found that some girls may prefer enjoyable activities that are non-skill-based, provide social opportunities, along with having a variety of activities to choose from, and the autonomy of which activity to participate in (16,(31)(32)(33)(34)(35). Alternatives to competitive sports with a focus on physical fitness and enjoyment could help adolescent girls develop positive PA habits according to their abilities and skills, which could, in turn, increase the likelihood of lifelong engagement in PA (16,33).
Environments outside of the school setting, such as the constructed setting of parks, sidewalks, street lights, distance to school, and the neighborhood that one lives in have found an influence on the PA levels in adolescent girls (42,47,48), which is in accordance with findings from this review.

Limitations
Notwithstanding, there are limitations that must be considered when interpreting the findings from this synthesis. Although this SR aimed to identify key barriers and facilitators for adolescent girls on a global level, we acknowledge that adolescent girls may face different obstacles unique to their social, cultural, and regional contexts that cannot be generalized in this review.
A major gap highlighted in this review is that most of the SRs included studies that were primarily conducted in highincome settings. As the global disparities of PA continue to rise in adolescent girls, additional interventions and research is needed throughout diverse regional settings due to the potential contextual variances in PA norms and environmental situations (15,16,49).
Despite that general implications can continue to be warranted to an extent, it is important to also note that differences in perceptions of barriers and facilitators in adolescent girls could relate to how active or inactive a girl is, as some evidence discovered not all girls prefer the same type of activities (16,33). In addition, some barriers and facilitators explicitly mentioned for adolescent girls in this review may also affect adolescent boys to some extent, given the adolescent period of social pressures and norms.
One limitation worth noting is that the SRs included in this review did not exclusively reflect adolescent girls aged 10-19, as some reviews reported on both sex and a variety of age ranges. Therefore, some barriers and facilitators may not be representative for adolescence, but also for transition periods, such as childhood and early adulthood. By including studies in both sexes, it allowed us to highlight the limitation that barriers and facilitators mentioned in this review may not only affect adolescent girls, thereby highlighting the difficulties placed in providing a clear gender-responsive direction in targeting interventions. For example, SRs included in this study that investigated both genders identified a few common barriers across genders, such as lack of time (30,33), perceived skill level (33,36), and family support (33,34,36).
Furthermore, included SRs were ranked as having low methodological quality. However, besides the AMSTAR 2 Tool being described as adequate for the assessment of the methodological quality of SR of SRs, this tool is more appropriate for healthcare interventions and not for studies of a qualitative nature. Therefore, results should be interpreted with caution.

Implications for Action
The findings of this review aimed to provide a backdrop of considerations for policymakers and implementers when taking a gender-responsive approach to the promotion of PA in adolescent girls. Based on the evidence synthesized in this review, key courses of action can be applied in practice.

Inclusive Approach to Curriculum Development to Address Gender Norms
It is necessary to have an inclusive approach to curriculum development for adolescent girls to address their specific needs. An Intersectoral approach involving education, sports, and health sectors should be considered in designing PE curricula that place a gender-responsive view of preferences of adolescent girls. This may require policies within the education and sports sector that can hold accountable the gender-responsive targeted action required in these modifications.
More dialog addressing harmful gender norms in the settings where PA takes place may help identify and address the barriers that discourage participation (33). Examples may include involving institutions, teachers, and boys in recognizing and addressing their own contribution to enabling these norms and encourage fostering a supportive environment for PA participation of girls. A curriculum that is non-competitive, flexible, individually created with a variety of opportunities, and the time to perform PA are some examples of how to adapt to the preferences of adolescent girls. Policies and initiatives that can support PA outside the traditional PE setting in schools, such as active breaks and active extracurricular activities are additional ways to encourage increase PA opportunities.

Adequate Training of Professionals to Ensure Inclusion of Adolescent Girls
Adequate training of professionals is required to equip them with the knowledge and skills to provide an inclusive PA environment for adolescent girls. Trained professionals should possess the understanding of the negative implications of lack of support provided to PA of girls, regardless of skill level and strategies on how to be more gender-responsive in their support provided specifically to girls. Qualified professionals should consider focusing on increasing physical literacy at earlier ages to build the confidence and skills required to maintain adequate PA levels throughout adolescence (50). Policies should be in place to ensure continued professional development and the availability of appropriate resources and material to provide gender-responsive PA strategies in school and sports club settings. Strategies and proper training of parents and peers to provide support for the PA participation of girls should also be considered due to its strong influence in facilitating PA (16,31,(33)(34)(35). Examples of ways in which parents and peers can encourage PA support in girls include participating in PA with adolescent girls and providing positive reinforcement for conducting PA (41). Interventions that can provide family participation and engagement in PA should also be considered.
Environmental Changes in and Out of Schools to Stimulate Participation, to Allow Adolescent Girls to Be Active in a Safe and Attractive Environment It is essential to stimulate PA participation with environmental modifications. Increasing access to safe and comfortable physical infrastructures and facilities for the use of adolescent girls should be a priority within and outside the school setting. Cost-effective PA interventions are needed so that they can be delivered with limited resources with little to no cost to families and increasing family support and participation of all children and adolescents, but with special attention toward techniques that can encourage adolescent girls specifically (33).
Policies that aim to provide equal opportunities regardless of gender and financial resources to tackle the larger structural barriers toward PA participation in adolescent girls are required. At the local level, policies and initiatives should address how public open spaces can be rendered more appealing to girls regarding safety and accessibility by addressing their specific concerns.
Community mobilization and engagement are necessary to foster a conducive environment supportive for the participation of adolescent girls in these spaces. Schemes that can encourage active travel to and from school are other ways in which schools and local authorities can work together toward increasing PA opportunities. In addition, recreational PA initiatives that can encourage peer engagement of adolescent girls should also be considered.
Multistakeholder Support at the Local, Regional, and National Level in Incorporating a Gender-Responsive Approach Toward PA Participation For the promotion of PA to be effective, it is essential for multistakeholder engagement at the individual, community, cultural, political, and environmental levels (51). Investing in policies that encourage PA for adolescent girls across these levels in and outside the school setting is deemed necessary for taking a gender-responsive action toward PA promotion. For example, active commuting to and from school has been described as a way to enhance PA practice, but this can be compromised if other measures are not implemented, such as safe sidewalks and cycle paths that provide routes to school along with neighborhood safety (8,52,53).
At the country level, leadership and coordination across sectors are fundamental to maximize the response required to address low levels of PA of adolescent girls. Ensuring national measures are taken to promote gender equality in PA can be reflected in policies that support gender-relevant forms of activity, particularly in school and recreational time, which can decrease sedentary leisure time activities (25).
The attainment of effective policies that increase PA levels in adolescent girls will contribute to meeting SDG number five, by promoting gender equality and the empowerment of girls at all levels, both essential for a peaceful, prosperous, and sustainable world (24). Gender equality and norms are strengthened and integrated during the adolescence period, when transitions to individualized identities, sexual activity, labor force participation, and marriage may occur. Interventions in the early stage in patterns of health behaviors, such as PA, will influence health trajectories over the life course (27).

Future Research
Despite the available evidence on the multiple barriers and facilitators that influence the PA of adolescent girls, research is required in terms of appropriate theoretical frameworks that can provide a clearer way to illustrate the multifaceted factors that influence the PA participation of adolescent girls. Such evidence can guide intervention designs aimed to target the multiple influential factors for PA promotion of adolescent girls and provide a clearer picture of what a gender-responsive approach toward action can look like.
Future research on PA should explore the factors for increasing PA among specific subgroups of adolescent girls (e.g., low socioeconomic status, migrant, transgender, girls living with disability, and pregnant/post-partum adolescent girls) along with the barriers and facilitators of transition periods (childhood to adolescence and adolescence to adulthood) longitudinally, to further promote PA in a life-course approach. Further research should also explore developing and testing gender-specific and gender-transformative PA programs for this population to gain effective and evidencebased PA programs, good practices and policies, at local, regional and national levels, as well as its proper monitoring and evaluation. Such evidence is needed to disseminate practical recommendations from research for policymakers at different levels.

CONCLUSION
This SR of SRs highlights the collected evidence that there is a variety of factors that influence the PA of adolescent girls. Lack of support from peers, family, and teachers, and the lack of time were among the most frequent barriers for adolescent girls while the motivation for weight loss and support from peers, family, and teachers were the most frequent facilitators toward PA participation.
This study provided key areas for policy action to promote PA in adolescent girls, based on the most frequent barriers and facilitators experienced. For the attainment of effective policies and practices that increase PA levels in adolescent girls, a multisectoral and multilevel gender-responsive response is necessary.