Comparing and assessing physical activity guidelines for children and adolescents: a systematic literature review and analysis

Background The impact of declining physical activity and increased sedentary behaviour in children and adolescents globally prompted the development of national and international physical activity guidelines. This research aims to systematically identify and compare national and international physical activity guidelines for children and adolescents and appraise the quality of the guidelines to promote best practice in guideline development. Methods This systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) and reported using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Only national, or international physical activity and/or sedentary behaviour guidelines were included in the review. Included guidelines targeted children and adolescents aged between 5 and 18 years. A grey literature search was undertaken incorporating electronic databases, custom Google search engines, targeted websites and international expert consultation. Guideline quality was assessed using the Appraisal of Guidelines for Research and Evaluation II Instrument (AGREE II). Results The search resulted in 50 national or international guidelines being identified. Twenty-five countries had a national guideline and there were three international guidelines (European Union, Nordic countries (used by Iceland, Norway and Sweden), World Health Organization (WHO)). Nineteen countries and the European Union adopted the WHO guidelines. Guidelines varied in relation to date of release (2008 to 2019), targeted age group, and guideline wording regarding: type, amount, duration, intensity, frequency and total amount of physical activity. Twenty-two countries included sedentary behaviour within the guidelines and three included sleep. Total scores for all domains of the AGREE II assessment for each guideline indicated considerable variability in guideline quality ranging from 25.8 to 95.3%, with similar variability in the six individual domains. Rigorous guideline development is essential to ensure appropriate guidance for population level initiatives. Conclusions This review revealed considerable variability between national/international physical activity guideline quality, development and recommendations, highlighting the need for rigorous and transparent guideline development methodologies to ensure appropriate guidance for population-based approaches. Where countries do not have the resources to ensure this level of quality, the adoption or adolopment (framework to review and update guidelines) of the WHO guidelines or guidelines of similar quality is recommended. Trial registration Review registration: PROSPERO 2017 CRD42017072558.


Background
A growing body of evidence demonstrates the relationship between physical activity and positive health outcomes in children and adolescents [1], whilst excessive time spent in sedentary behaviours, and particularly screen time, is negatively associated with health outcomes [2,3]. Over the past three decades global concerns regarding declining levels of physical activity and the subsequent impact on health outcomes prompted several national and international governing bodies to develop guidelines providing recommendations for policy makers, practitioners and individuals [4,5]. Early iterations of physical activity guidelines for children were based on adult recommendations [5]. In 1994 the United States (US), was the first country to produce physical activity guidelines specifically customized for adolescents [6], which were later followed by guidelines for 'school aged youth' in 2004 [7]. Over this period of time, the United Kingdom, Canada and Australia released guidelines for children and youth [8]. In the past decade there has been a trend encouraging a more transparent and rigorous approach [9] to guideline development with growing bodies of evidence and more recent guideline development frameworks Appraisal of Guidelines for Research and Evaluation II Instrument (AGREE II) [10]. Canada released the world's first stand-alone sedentary behaviour guidelines for children and youth in 2011 [11]. More recently national and international bodies have included recommendations for sedentary behaviour in their physical activity guidelines due to the growing body of evidence linking excessive sedentary behaviour to poor health outcomes [2,3]. Much of this evidence centred on screen-based sedentary pastimes [2,3]. In 2016, Canada became the first country to replace their national physical activity and sedentary behaviour guidelines for children and adolescents with 24-h movement guidelines, which consider behaviours across a '24-hour movement spectrum' and also included recommendations for sleep [12]. New Zealand adopted the Canadian guidelines in 2017 and Australia used the Grading of Recommendations Assessment Development and Evaluation (GRADE) recommended GRADE-ADOLOPMENT approach to develop 24-h movement guidelines from the Canadian guidelines in 2019 [13]. This approach is a structured, transparent, cost effective process to review and update guidelines based on an evidence-to-decision framework using previous guideline systematic reviews which are updated to reflect the date of guideline development.
As the evidence-base supporting guideline development continues to grow, more countries have implemented guidelines to inform parents, health professionals and policy-makers of recommended levels of physical activity for children and adolescents [14]. In the past 5 years, numerous countries have reviewed or updated their physical activity guidelines for children and adolescents, with a trend towards more robust evidence-based guidelines. Cross-country comparisons of guidelines revealed variability in age categories, activity duration, intensity, frequency, type of activity/sedentary behaviour and overall guideline quality [14]. With escalating rates of non-communicable disease globally, prevention is imperative; evidence-based, high quality physical activity guidelines are essential to guide practitioners, professionals, policy makers and the public, and avoid confusion and misinterpretation of the underlying evidence-base. The purpose of this systematic review was to identify national and international organizations with existing official physical activity and/or sedentary behaviour guidelines for school-aged children and adolescents (5-18 years), appraise the quality of the guidelines, draw comparisons between the guidelines, and recommend standards to promote best practice and opportunities for cross-country comparisons.

Design
This systematic review was registered with the International Prospective Register of Systematic Reviews (PROSPERO; Registration no CRD42017072558) [15]. It is reported using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement for reporting systematic reviews and meta-analyses [16].

Information sources and search strategies
The search strategies for this review were developed during the meeting of co-investigators (AMP, TO, DC, SV, MT). Two research librarians then provided expert advice to further develop and refine the strategy. As most documentation for the review is not commonly found through scholarly literature sources, it was determined that the most appropriate methodology would be to use a grey literature search plan [17]. This strategy was adapted from a previous review that used grey literature search methods to examine guidelines for breakfast programs in Canada [17]. For a guideline to be included in this review it had to incorporate a statement from a national or international institution outlining the physical activity and/or sedentary behaviour recommendations for children and adolescents between the ages of 5 and 18 years, as defined in the review eligibility criteria in Table 1 [17]. There were no language restrictions. Records included peerreviewed journals and grey literature sources of guideline documents or webpages published between January 2010 (the date that the World Health Organisation released the first international guidelines) [18] and the date of the searches. Key search terms included: "physical activity", "exercise"; "guideline*", "recommendation*"; "child*", "youth", "adolescen*", "school aged", "young pe*", "child*".
The grey literature search involved four search strategies: (1) grey literature databases, (2) custom Google search engines, (3) targeted websites, and (4) consultation with content experts [17]. The grey literature database search included PubMed, ProQuest and CINAHL databases. These databases were selected upon consultation with the University research librarians and were deemed appropriate due to their ability to include grey literature. The search of these databases commenced on the 18th July 2017 (BS) and concluded on the 20th of July 2017 (BS) (see Additional files 1, 2 and 3 for more detail). Records identified in this search were extracted from the online interfaces and imported into EndNote referencing software [19] The search was re-run and updates made on the 7th March 2019 (AMP and SLCV).
The Google search included Google and Google Scholar. This search was limited to and included sources from 2010 when the last iteration of the World Health Organisation (WHO) were released until March 2019. Google searches yield an overwhelming number of results, due to the fact that Google search engines use relevancy ranking bringing the most relevant sources to the top of the search results. In keeping with previous research [17], the first 15 pages (150) results were included in the review. In addition, pages 16 and 17 of the Google search results were manually checked to ensure the relevancy of this method. These results were tagged and imported into Zotero software [20] and then transferred into the EndNote referencing software [19].
The third search included targeted websites of government and health organizations. The first targeted web search occurred on the 18th of July 2017 and was updated in March 2019. This search included the following sources: the WHO website, EuroScan International Information Network, International Network of Agencies for Health Technology Assessment (INAHTA), OpenGrey and WorldWideScience. In addition, the following limiters were used in the Google search engine: site:org and/or site:gov. Records identified in this search were extracted from the online interfaces into Zotero [20] software and then transferred into the EndNote software [19].
The final search strategy involved contacting content experts to seek their recommendations for document inclusion in the review. The Active Healthy Kids Global Alliance organised a Global Matrix on physical activity for children and adolescents, involving leading international experts from 49 countries who participated in the preparation of national physical activity report cards for children and adolescents [21]. Designed to raise awareness of physical activity participation levels, the report cards assign grades to physical activity indicators based on country specific data. These experts were contacted and surveyed in March 2019 to identify which report card they had led, which physical activity and/or sedentary behaviour guidelines they followed, and the associated links to guideline documents (Additional file 3). Identified guidelines and associated documentation were manually entered into the EndNote software [19].
Once identified records were all entered into the Endnote software, de-duplication took place prior to proceeding to level one screening and all duplicates were removed as were books, magazines and newspapers ( Fig. 1). Level one screening included independent screening of relevant titles and abstracts, webpages and guideline documents by the two reviewers (BS and AMP; SLCV and AMP update). Any document included by one reviewer and not the other was retained for further review at level two. Level two involved examination of potentially eligible full text documents or webpages that were retrieved and independently assessed for eligibility by the two review team members (BS and AMP; SLCV and AMP update). The reference list of relevant review papers was manually checked for papers potentially missed by the search. The homepage of relevant webpages was searched for potentially relevant documents. Disagreements regarding eligibility of guideline documents were resolved through discussion with a third reviewer (ADO or DC). A standardised, pre-piloted form was used to extract data from the included documents to allow assessment of quality and evidence synthesis. The form included: country, name of guideline, issuing authority, date of release, age group, recommended physical activity duration, intensity, frequency, type and sedentary behaviour recommendation ( Table 2). Data extraction was completed by one reviewer (AMP) and verified by another reviewer (DC).
If a document stated that a country used more than one guideline to create their country's guideline (e.g., WHO and Centre for Disease Control (CDC)), the guideline was included in Table 2. In some instances, experts indicated that their country had a national physical activity guideline; however if there was no documented evidence to support this claim it was not included. In other instances, experts stated that the country's guideline was based on either the WHO, CDC or Canada's physical activity guideline, however, if this could not be verified with documented evidence, these countries guidelines were not included.

Guideline quality
The quality of each national and international guideline was assessed using AGREE II. The original instrument was developed in 2010 and was updated in 2017 [10]. It includes six categories and 23 items with 7-point Likert scales. The AGREE II instrument is a valid and reliable instrument for assessing guideline quality [22,23]. Assessors used the AGREE II Instrument manual and online training tool [10]. Two people independently assessed each guideline. Ten assessors (AMP, SC, KHC, MNE, BdPC, SA, MJS, CT, YE, ZZ) were involved in appraising the guidelines using the AGREE II instrument due to the variation in languages. As per AGREE II instrument guidelines, quality scores are calculated for each of the six domains by 'summing all the scores for each of the individual items in a domain and scaling the total as a percentage of the maximum possible score for that domain' [10]. Guidelines from 27 countries were evaluated by at least two appraisers. In instances where the two assessors' evaluation of AGREE II items varied by a margin of more than two points, assessors revisited the item to find a consensus to reduce the gap in the margin of their assessment. In four instances a third assessor was consulted to assist in this process, due to the unavailability of the original reviewer.

Countries with guidelines
The search resulted in the identification of 50 verified national or international guidelines on physical activity and/or sedentary behaviour for children and adolescents (Table 2 and Fig. 2). A quick summary of the guidelines can be found in Table 3. Twenty-five countries had national guidelines. There were three international guidelines including the European Union [24] (which follows the WHO guideline), the Nordic [25] (Iceland, Norway and Sweden used these guidelines) and the WHO guidelines [18]. The WHO guidelines were adopted by 19 other countries and by the European Union. No countries made specific reference to the European Union guidelines. Countries that based guidelines on the WHO physical activity guidelines [18] or the Nordic Nutrition guidelines [25] are mentioned at the bottom of Table 2. For three national South Africa [26]; Estonia [27]; Kenya [28] and one international guideline (Nordic) [25], the physical activity guidelines were incorporated into nutrition/ dietary guidelines. Venezuela and South Korea were believed to have a national physical activity guideline, however a guideline could not be found. Croatia, Cyprus and the Czech Republic had customized WHO country factsheets; however, the factsheets stated that they did not have a national guideline and that it was under development. Some national guidelines were identified as following either the WHO [18], Canadian [29] or the United States [30] physical activity guidelines, yet no documented evidence could be found; these countries included: Brazil (WHO), Columbia (WHO), Mozambique (Canadian), Nigeria (Canadian), Thailand (WHO), United Arab Emirates (WHO and United States), and Zimbabwe (WHO).

Guideline content
Date of guideline release and age category The date of release of the guidelines ranged from 2008 to 2019. There was considerable variability between the age categories specified in the guidelines for children and adolescents (refer to Table 2). Age categories for children and adolescent guidelines ranged from 0 to 21 years of age. The most common category was 5-17 years 12 countries/international guidelines used this age category including: Argentina [31], Australia [32], Canada [29], Malaysia [33], Mexico [34], New Zealand [35], Paraguay [36], South Africa [26], Spain [37], Turkey [38], WHO [18] and Qatar [39] (Qatar also had sub categories of 5-12 years and 12-17 years). Further details of variation in this category can be found in Table 2.

Physical activity duration
More homogeneity existed between guidelines in reference to 'time spent' being physically active. All except one country (Germany [40]) indicated that children should participate in 60 min of physical activity daily; however there was variability in the wording of the           recommendations. Germany recommended 90 min or more ("60 minutes on every day activities e.g., at least 12,000 steps"). More detail regarding slight wording variations can be found in Table 2.

Bouts of physical activity
Seven guidelines referred to bouts of physical activity. Two guidelines mentioned bouts of 'several sessions throughout the day (e.g., 2 bouts of 30 min) (Paraguay [36], Turkey [38]); two suggested several bouts of aerobic activity/brisk exercise of at least 10 min duration (Chile [42], Finland [54]) ( Table 2); one recommended three sessions of at least 20 min of "high intensity" physical activity on non-consecutive days (France [43]); and another indicated activities could be performed in multiple shorter periods throughout the day (Mexico [34]). The Philippine guideline [51] was ambiguous recommending 'at least 20 min of sustained MVPA continuously for a minimum of 30 mins or accumulated bouts of 10 min or longer for children aged 13 to 20 years'.

Sedentary and screen time
Seventeen countries mentioned the need to reduce sedentary time. The wording of recommendations for sedentary time varied (refer to Table 2). Ten countries advised limiting sitting/sedentary time for extended/long periods (Australia [32], Canada [29], China [50], Netherlands [52], New Zealand [35], Nordic [25], Spain [37], Switzerland [46], Turkey [38], United Kingdom [47]). Two countries used specific time periods; Austria recommended 'avoiding long periods of inertia, punctuate periods lasting two or more hours with active stints of physical activity' [41] and Finland advised 'not to sit still continuously for longer than one hour' (Finland) [54].

Guideline quality
The AGREE II appraisal of each country or international physical activity guideline is provided in Table 4. The domain scores were calculated using the AGREE II Instrument calculation. The scores for each of the six domains were as follows: Scores for

Discussion
National and international physical activity and sedentary behaviour guidelines serve as important tools for health professionals, policy makers, researchers, teachers, parents and children/adolescents. As knowledge of the determinants of physical activity and sedentary behavior among children and adolescents increases, along with a rapid expansion of the evidence base pertaining to the health benefits of different types and duration of physical activities, regular revision and updating of relevant guidelines is essential. This review provides a summary of national and international physical activity and sedentary behaviour guidelines for children and youth a comprehensive summation and insight into guideline quality and variability, whilst highlighting the importance of cross-country comparisons for epidemiological purposes.
While it is acknowledged this review may have been limited by the ability to search in different languages, it is likely that there is still a majority of countries without physical activity and sedentary behaviour guidelines governing and guiding policy and practice. Alternatively, there may be countries who adopt the WHO guidelines without specifically stating it. Guidelines are designed to provide recent evidence-based information that aligns with the recommendation to encourage healthy behaviour [55]. With the increasing burden of the noncommunicable disease impacting low, middle and high income countries, reducing risk factors by improving healthy lifestyles is key in the management of this global challenge.
The WHO advocates for multi-sectoral approaches to address declining levels of physical activity, urging governments to develop policies which support interventions to increase physical activity and reduce sedentary behaviour [55,56]. The current WHO physical activity and sedentary behaviour guidelines are 9 years old, with current plans to update these guidelines in place [18]. As a global leader in the promotion of public health, the WHO provides policies and recommendations that are particularly pertinent for low-and middle-income countries that may not have the resources to appropriately develop or revise physical activity and sedentary behaviour guidelines. The WHO advocates for "scientificallyinformed recommendations with a global scope on the benefits, type, amount, frequency, intensity, duration and total amount of physical activity necessary for health benefits" [18]. With a growing body of evidence in the sector it is imperative to update these guidelines on a regular basis and where possible to develop culturally adapted guidelines. Updating guidelines is also essential in a climate of rapid technological change. The findings from this review found several guidelines were written between eight and 10 years ago [18,44,45,47,51,54]. The changes in technology during this timeframe reflect a number of new barriers impacting children's ability to meet physical activity and sedentary behaviour guidelines. The availability of technologies such as smartphones, laptops, tablets, and gaming consoles as a normal commodity for children has made restricting screen time a difficult task resulting in increased sedentary screen time while impacting opportunities for activity. As indicated in the AGREE II assessment (domain 3 question 14), when guidelines are implemented it is important to include a plan for future review and update [10]. Only four national/international guidelines included a plan to review and update guidelines [18,29,32,52].
There was considerable variability in the age specifications of national guidelines for children and adolescents, which may be the result of cultural differences in formal schooling. Physical activity participation and engagement varies over the life course, there is a notable decline in physical activity as children transition from childhood to adolescence [57]. Some national child and adolescent physical activity and sedentary behaviour guidelines described age groupings which included pre-schoolers and adults [42,51]. Guideline age groupings should aim to accurately reflect developmental periods to provide appropriate recommendations for the age they are targeting. In some instances age groupings overlapped creating ambiguity in their application (e.g. The Netherlands: 0 to 4 years and 4 to 18 years -and Australia: 0 to 5 years and 5 to 17 years with the distinction that children who were not at school should follow the early years guideline and those at school should follow the 5-17 year guideline) [32,52]. Further, small differences in guideline wording impact cross-country comparisons. Five countries used categories rather than age ranges with terms such as 'school aged children' (Switzerland, Austria) and 'children and adolescents' (Nordic, Ghana) and '5 years to pre-pubertal and adolescents' (Uruguay). Subjective categories may lack clarity required by end-users and make cross country comparisons more difficult. Further, terms such as 'young people' or 'youth' do not accurately reflect the age grouping of child and adolescent guidelines. Youth are defined by the WHO and the United Nations as "individuals in the age grouping 15 to 24-year olds" [58,59]. There is more ambiguity associated with the terminology 'young people': the United Nations Educational Scientific and Cultural Organization (UNESCO) uses the terms 'young people' and 'youth' interchangeably referring to "individuals aged between 15 and 24 years of age" [60]. The Australian Institute of Health and Welfare refers to young people aged 12 to 17 years and young people aged 15 to 24 years [61]. Regardless, these definitions indicate that there is potential for terminology to inaccurately target the correct age grouping for the guidelines. The parameter with the most consensus across the guidelines was the recommended time spent in physical activity per day. Nineteen guidelines recommended a minimum of 60 min of MVPA each day. Only one country (Germany) recommended 90 min or more of MVPA every day. However, there were slight variations in the wording of recommendations that can affect the interpretation of the guideline. Four countries recommended 60 min per day, and end users may interpret this as the required amount of time for health benefits without considering any added gains from additional time spent in MVPA [62]. Even small variations in wording could result in misinterpretation. For instance some countries indicated VPA should be incorporated 3 days per week, while others say at least three times per week, which may be confusing for stakeholders. Potentially a child could fulfil the vigorous physical activity guidelines in 1 day if they were to follow the guideline wording 'three times per week'.
The Nordic countries [25] and South Africa [26] embedded their physical activity guidelines into the national nutrition/dietary guidelines. Estonia [27] combined the nutrition and physical activity guidelines. Whilst these guidelines were comprehensive, it is possible that physical activity guidelines may become lost in nutrition/ dietary guidelines, with potentially less opportunity to rigorously review physical activity evidence in its development. Similarly, some countries (Germany [40], Netherlands [52], Philippines [51]) developed a document that included physical activity guidelines across the age spectrum. Whilst these documents were thorough, it is possible that child and adolescent studies to inform the review may have been missed if separate, rigorous search strategies were not conducted, potentially affecting the robustness of the recommendations. These guideline development panels may be limited by a lack of child/adolescent physical activity experts.
There is growing evidence supporting the health impact of regular physical activity in children and adolescents [1,43]. There is also a growing body of research linking sedentary behaviour and poor health outcomes [2]. The inclusion of sedentary time in guideline development is crucial as children currently spend between 50 and 60% of their day sedentary often replacing physical activity with sedentary, time [2]. Most countries now recognise the health impact of sedentary time on children's health outcomes, reflected by the inclusion of sedentary behaviour recommendations in 22 of the 29 national and international guidelines. In a recent review, higher levels of screen time were associated with poorer health outcomes with a gradient effect, however the evidence for sedentary behaviour was not consistent [2,63]. With this in mind and considering the rapid growth in the technology sector (hand held devices, TV, computer, gaming platforms) it is important that guidelines make recommendations to direct stakeholders regarding screen time. However the variability in current sedentary behaviour guidelines reflect the infancy of current evidence to provide a more exact position on the recommended amount of time spent sedentary.
More recently, the potential importance of health opportunities across the entire day have resulted in the implementation of 24-h movement guidelines, with Canada implementing the first 24-h movement guidelines for children and adolescents [12]. The Canadian guidelines combine recommendations for physical activity, sedentary behaviour and sleep for a 24-h period rather than a set of segregated guidelines [12]. Several countries have followed this trend towards 24-h movement guidelines, with New Zealand adopting the Canadian guidelines and Australia 'adoloping' the guidelines [64]. Importantly future systematic reviews of physical activity guidelines should incorporate '24-h movement' and associated variations into the search terms to ensure these guidelines are not omitted.
The AGREE II appraisal of guidelines revealed considerable variation in the quality of physical activity guidelines demonstrated by the 'overall quality score' ranging from 25.8 to 95.3% (Mean = 61%). Four of the domain average scores were lower than 50%. Domain 3 (rigour used to synthesize and formulate guidelines) is arguably one of the more important domains when assessing quality of guideline development, yet the scores (range 1.5 to 99%; Mean = 35%) indicate a need for more rigorous evidence based development to ensure guidelines are as evidence based as possible [10]. The diversity in the quality of the guidelines were likely to have been impacted by the year they were developed (as recent iteration of guidelines follow a more rigorous evidence based approach) and the socioeconomic status of country (with poorer countries less likely to have the same funding or expertise to support the development of the guideline). Notably the overall AGREE II score for the WHO guideline development was higher than 90% (and will soon be revised). In instances where countries are not able to provide the same level of quality, it is recommended that the WHO Guidelines be used or the GRADE-ADOLOPMENT approach be followed [64].
In the past 10 years there has been a movement towards more rigorous processes for guideline development [12]. Notably, this review has disclosed considerable betweencountry variability in guideline quality and development. Scientific legitimation is one of the key factors for guideline implementation [55,65]. In instances where guidelines provide advice without current research to support the recommendation, it should be acknowledged. Health professionals, researchers, and the public rely on the legitimacy of national/international guidelines as a reference point when encouraging healthy lifestyles.
There are several strengths and limitations of this review. The grey literature search enabled a diverse comparison of guidelines that included those that were not written in English; however there may be subtle changes in language between guidelines as they were written in different languages. As a result of the number of guidelines and the diversity in the language of the guidelines only two assessors conducted the AGREE II quality assessment on each of the guidelines. While it is acceptable to have two assessors conduct the AGREE II assessment, it is preferable for up to four assessors to conduct this assessment [10]. Further it was not feasible to have the same assessors conduct the quality assessment of all the guidelines due to the language variation. Further, potentially some guidelines were not captured in this review, as it was not possible to include search terms in all languages. It is also possible that some countries have screen-related guidelines that are separate to their physical activity guidelines, and these may not have been captured in this review.

Conclusion
There is growing global interest in physical activity and sedentary behaviour guideline development. More recently some countries have included sleep in their guidelines focusing on movement behaviours during a 24 h period.. The findings from this review indicate extensive variability in the quality of country guidelines. Rigorous guideline development is essential to ensure appropriate guidance for population level initiatives. However, low income countries may not have the resources or expertise for guideline development. It is recommended in these instances that the WHO guidelines be used or the GRADE-ADOLOPMENT approach be followed to adopt, adapt, or develop appropriate guidelines for their context.
Additional file 1. Data base search results.