Journal of Science and Medicine in Sport 18 (2015) 418–425

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Review

Physical activity temporal trends among children and adolescents Verity M. Booth ∗ , Alex V. Rowlands, James Dollman School of Health Sciences, University of South Australia, Australia

a r t i c l e

i n f o

Article history: Received 8 November 2013 Received in revised form 23 April 2014 Accepted 1 June 2014 Available online 12 June 2014 Keywords: Trends Child Physical activity Sport Active transport Physical education

a b s t r a c t Objectives: It is particularly important to measure trends in physical activity to identify specific contexts where physical activity may have declined and can be targeted for intervention. The aim of this review was to summarize overall physical activity trends based on objectively measured physical activity as well as trends in specific contexts (active transport, organized sport, school physical education and school play periods) using self- or proxy-reported physical activity. Design: A comprehensive literature search was completed to identify articles on the specific contexts of physical activity for inclusion in this review. Methods: Journal articles for inclusion in this narrative review were sourced from the various databases and reference lists. Most studies in this review employed self-report or proxy-report methodologies. Results: There is limited research on temporal trends in children’s and adolescents’ physical activity. The few studies that employ objective measures to assess trends in physical activity indicate little change has occurred in the last 20 years. Other studies that employed self-report methods indicate organized sport trends are somewhat inconsistent across countries, however most studies reported an increase in participation. Within the limited physical education trend studies, inconsistent trends were noted. There have been consistent declines in active transport, particularly cycling. Few studies have investigated trends in physical activity and sedentary behaviour during school play periods, highlighting a need for further research. Conclusions: Mixed results and inconsistent magnitudes of change were identified when exploring trends in different contexts of physical activity for children and adolescents over the last few decades. Taken overall, there is little evidence for a decrease in children’s and adolescents’ physical activity, although consistent declines in active transport highlight this context as a suitable intervention target. © 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

1. Introduction

2. Current physical activity levels

Since physical activity (PA) contributes 18–29% of daily energy expenditure, it has become an important focus for research into unsatisfactorily high rates of child overweight and obesity.1 As well as assessing the total PA that children undertake, it is particularly important to measure trends in PA to identify specific contexts where PA may have declined and can be targeted for intervention. This is an update of a previous review,2 describing recent trends in the following distinct PA contexts: active transport (AT); organized sport; school physical education (PE) participation; and PA during school play periods.

World Health Organization3 guidelines recommend that children and adolescents between ages 5 and 17 years accumulate a minimum of 60 min of moderate to vigorous PA (MVPA) per day3 to achieve health benefits. A 2008 Western Australian study involving 1827 participants used self-report to identify that 27% and 41% of primary age girls and boys, respectively, and 10% and 37% of secondary age girls and boys, respectively, met recommended guidelines.4 In the same study, pedometer steps were compared with recommended step cut points established using BMI-referenced weight categories;5 44% and 32% of primary age girls and boys, respectively, and 38% and 42% of secondary age girls and boys, met these recommendations. Regardless of measurement approach, in this sample less than half of young people met the recommended PA levels for health. Few developed countries report a high prevalence of children meeting the recommended daily MVPA. For example, self-report data show that only 19–38% of 12–17 year olds in the United

∗ Corresponding author. E-mail address: [email protected] (V.M. Booth).

http://dx.doi.org/10.1016/j.jsams.2014.06.002 1440-2440/© 2014 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

V.M. Booth et al. / Journal of Science and Medicine in Sport 18 (2015) 418–425

States of America (USA)6 and 15–33% of 9–15 year olds in England7 participate in 60 min or more of daily MVPA. These nationally representative studies involved 7521 and 15,425 participants from USA and England, respectively. Further, self-report data on 11 year olds from various European countries show that 37% (Russia) to 80% (Ireland) of boys and 23% (Portugal) to 70% (Finland) of girls participated in 60 min of MVPA on at least 5 days per week.8 Physical activity report cards from developing countries highlighted that 58.5% of South African children,9,10 35.2% in Mexico11 and 72% in Kenya12 participated in sufficient MVPA. 3. Methods Journal articles for inclusion in this narrative review were sourced from the following databases: ERIC; MEDLINE; SportDiscus; Ovid; Cochrane Library; Google Scholar; Informit health databases; PubMed; ProQuest family health; and CINAHL database. Search terms used consisted of a combination of: child; adolescent; schoolchildren; physical activity; trend; sport; active transport; recess; lunch; physical education; PE; self-report; objective; pedometer; and accelerometer. Some studies were also sourced from reference lists. Most studies in this review employed self-report or proxy-report methodologies which are relatively convenient and therefore most prevalent in the literature. While most reports of trends rely on such studies, conclusions are limited by error occurring through poor recall, mis-interpretation of the question and social desirability bias.13 Objective measures, including pedometers and accelerometers are becoming more prevalent in trend studies, however are limited by the lack of availability of consistent baseline data with which to compare current data and often have smaller sample sizes, thus limited generalizability, compared to self-report studies. 4. Trends in physical activity There is limited research on temporal trends in children’s and adolescents’ PA, in part due to inadequate baseline data, methodological inconsistencies between studies and a lack of research into specific PA contexts. Two recent reviews of temporal trends in PA participation of children and adolescents have suggested that PA may be declining,2,14 although results are mixed and inconsistent.2,14,15 The aim of this review was to summarize overall PA trends based on objectively measured PA as well as trends in specific contexts (AT, organized sport, school PE and school play periods) using self- or proxy-reported PA (see Table 1 for a list of studies). 5. Trends in overall physical activity Few studies have investigated trends in PA using objective measures, with only three studies from Sweden, Czech Republic and Denmark identified in this review. Two of these studies used pedometers to record steps per day17,18 and the other used accelerometry.16 Swedish researchers17 assessed steps per day using a sealed Yamax pedometer in 429 adolescents aged 13 and 14 over four consecutive school days in 2000 and 2008 (see Table 1 for sample size by time-point for each study). No differences were found for boys (15,623–15,174 steps d−1 ) and girls (12,989–13,338 steps d−1 ).17 It was noted that during this time span, interventions were initiated within Swedish schools to provide children and adolescents with daily structured PA during school time, but it was apparent that these initiatives had little impact on daily steps. Sigmundová et al.18 used pedometers to measure steps d−1 in 902 adolescents aged 14–18 years between 1998 and 2010 in the

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Czech Republic, with measurements at each time point conducted over seven consecutive days. The study found a decline in the percentage of boys who met the Czech health-related criterion recommendations of 11,000 steps d−1 , from 68% to 55%, while no change was observed among girls (75%–74%). A Danish study used accelerometers to measure overall PA, as average counts per minute, over 5 consecutive days between 1997–1998 and 2003–2004 among 797 children aged 8–10 years.16 No change was seen among either boys or girls regardless of socioeconomic status. Together these few studies traversing relatively brief time periods indicate little change in objectively measured PA. Ongoing surveillance using objective measures is warranted to detect trends over a longer time span.

6. Trends in specific contexts of physical activity 6.1. Organised sport Organized sport is often defined as participation in a club or school sport and the associated training sessions with the exclusion of physical education. One study in the USA revealed that this can account for 23% (26 min) of daily MVPA for boys19 while an Australian study suggested that this might be as high as 45% (43 min) of daily MVPA among adolescents.20 Another Australian study found that approximately one-third of the time girls’ were participating in organized sport sessions was spent in MVPA.21 Studies of organized sport trends included in this review were conducted in Belgium, Iceland, Hong Kong, United States and Australia (see Fig. 1). There was a range in the number and detail of questions used to quantify organized sport participation across the studies. A Belgian study investigated club sport participation, defined as at least one hour per week over a year, among a total of 22,424 high school students, every 10 years from 1969 to 1999.22 There was a statistically significant increase in the proportion of boys and girls who participated in club sport from 35% to 62%, and 30% to 51%, respectively, across the 30 years, representing a rate of change of 8% per decade for girls and boys. The authors also reported that family socio-economic status (SES) influenced trends in sport participation differently for boys and girls, with low SES boys’ participation increasing from 52% to 64% and high SES boys’ participation decreasing from 44% to 38%.22 The proportion of high (35–51%) and low SES (56–73%) girls’ participation increased similarly. Over a similar time span (1977–2005), the Finnish Adolescent Health and Lifestyle Survey was administered every 2 years to 12, 15 and 18 year olds, with each wave consisting of between 2832 and 8390 participants. Rates of increase in sport participation (at least once per week) during the period 1991–2005 were similar in low and high family SES, with an increase from 40% to 48% among low SES boys and 47% to 58% among high SES boys. Girls’ participation increased from 26% to 35% in low SES families and 38% to 50% in high SES families. Self-reported sport participation defined as club participation four or more times per week was assessed as part of The Youth in Iceland National Survey.24 An increase was observed from 17% to 37% among a total of 27,426 14–15 year olds between 1992 and 2006. Both boys and girls increased their participation by about +14 percentage points per decade. These three studies completed in four different European countries showed an increase in organized sport participation among children and adolescents, suggesting increases have occurred in northern and western Europe, with magnitudes of change ranging from +8 percentage points per decade in Belgium to +14 percentage points per decade in Iceland. A study of 8624 students aged 13–18 year olds in Hong Kong reported that the prevalence of extracurricular sports participation

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Table 1 Table of studies. Authors

In-text reference

Location and time period

Age and sample size

Studies investigating objectively measured overall physical activity 16 Denmark 8–10 years Møller et al. (2009) 1997–2004 N = 381 (1997/8) N = 416 (2003/4)

Methods

Main findings

Trend

Accelerometer

No evident change in physical activity levels



Raustorp and Ekroth (2010)

17

Sweden 2000–08

13–14 years N = 235 (2000) N = 186 (2008)

Pedometer

No significant change in physical activity levels.



Sigmundová et al. (2011)

18

Czech Republic 1998–2010

14–18 years N = 382 (1998–2000) N = 620 (2008–2010)

Pedometer and self-report

Boys achieving 11,000 steps per day decreased (68–55%). Girls also decreased (75.1–74%)

↓

Self-report The Australian Health and Fitness Survey

Organized sport remained stable, active transport decreased (cycling 20.6–5.4%, walking 39.9–36.7%), increase in PE participation, decrease in physical activity in school lunch periods.

OS  AT ↓ PE ↑ SPP ↓

9–13 years N = 557 (1985) N = 926 (2001)

Self-report The Australian Health and Fitness Survey

Decrease in frequency of walking and cycling to school. Decrease in PE participation for 2 times per week. Increase in school sport frequency.

AT ↓ PE ↓ OS ↑

5–14 year olds N = 5825

Proxy-report Children’s Participation in Cultural and Leisure Activities Survey

Organized sport participation increased from 64% to 67% to 68%

↑

Studies investigating more than one context of physical activity 29 South Lewis et al. (2007) 9–15 years Australia, N = 393 (1985) N = 392 (2004) AUS 1985–2004

Salmon et al. (2005)

30

Victoria, AUS 1985–2001

Studies investigating organized sport participation 28 Australia Australia Bureau of Statistics (2007) 2000–2006

Eiosdóttir et al. (2008)

24

Iceland 1992–2006

14–15 year olds N = 7018 (1992) N = 7785 (1997) N = 6352 (2000) N = 7430 (2006)

Self-report Youth in Iceland national survey

Organized sport participation increased from 17.2% to 31.7%.

↑

Huhman et al. (2012)

26

USA 2002–2006

9–13 years N = 3114 (2002) N = 5177 (2004) N = 1200 (2006)

Self-reported Youth Media Campaign Longitudinal Survey

Stable or a slight increase of sport participation from 39.5 to 40.9 to 42.4%



Mak and Day (2010)

25

Hong Kong 1995/96 – 2000/01

13–18 years N = 2932 (1995/6) N = 5692 (2000/1)

Self-report Health Related Behaviour General Survey

Boys’ sports participation decreased from 80.5 to 72% and girls remained relatively stable from 53.7 to 50.4%.

Boys ↓ Girls 

Martin et al. (2005)

27

Australia 1985–1999

10–13 years old N = 2463 (1985) N = 1469 (1997–1999)

Self-report questionnaire Australian Health and Fitness Survey

Boys’ participation in at least one sport declined from 87% to 76%, girls participation declined from 80% to 71%.

Boys ↓ Girls ↓

Scheerder et al. (2005)

22

Belgium 1969–1999

12–20 years old N = 12969 (1969) N = 5029 (1979) N = 2155 (1989) N = 2271 (1999)

Self-report questionnaire Leuven Growth Study of Belgian Boys; Leuven Growth Study of Flemish Girls; 2 other cross-sectional surveys

Boys club organized sport participation of once per week increased from 35–62% and girls increased from 30 to 51%

↑

Telama et al. (2009)

23

Finland 1977–2005

12, 15 and 18 year olds Measured every 2 years with samples of N = 2832 to 8390

Self-report Finnish Adolescent Health and Lifestyle Survey

Increase in sport participation for both low and high SES from 1991–2005

↑

Self-report

Significant decline in the percentage enrolled in PE at least once per week from 70.3% to 60.3%. Students attending daily PE remained stable 15 to 16.3%.

1 × wk ↓ 5 × wk 

Studies investigating school physical education participation 34 Canada Grades 9–12 Faulkner et al. (2007) 1995-2005 N = 1495 (1999) N = 1278 (2001) N = 4693 (2003) N = 5794 (2005)

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Table 1 (Continued) Authors

In-text reference

Location and time period

Age and sample size

Methods

Main findings

Trend

Lowry et al. (2004)

33

US 1991–2003

Year 9–12 N = approx. 14000

Self-report Youth Risk Behaviour Surveillance System

No significant change in PE participation 1 day per week, significant decline in students attending PE 5 days per week from 41.6% to 28.4%.

1 × wk  5 × wk ↓

Toronto, Canada 1986–2006

11–15 year olds N = 3411 (1986) N = 5385 (1996) N = 7193 (2001) N = 7301 (2006)

Self-reported telephone interview Transportation Tomorrow Survey

Walking proportion of trips to school declined 53–42.5% (11–13 yr olds) and 38.6–30.7% (14–15 yr olds). Cycling declined (2.2–1.2%)

↓

Studies investigating active transport 39 Buliung et al. (2009)

Costa et al. (2012)

40

Brazil 2002–2007

7–10 year olds N = 2936 (2002) N = 1232 (2007)

Self-reported

Active commuting decreased from 49% to 41%

↓

Cui et al. (2011)

42

China 1997–2006

6–18 years old N = 2454 (1997) N = 1978 (2000) N = 1549 (2004) N = 1236 (2006)

Self-reported China Health and Nutrition Survey

Active transport decreased from 99 to 88% (6–12 year olds) and 93 to 83% (13–18 year olds).

↓

Grize et al. (2010)

41

Switzerland 1994–2005

6–14 year olds N = 956 (1994) N = 1535 (2000) N = 1753 (2005)

Self-reported Swiss Microcensus on Travel Behaviour

Overall decrease in active commuting from 78.4 to 71.4%.

↓

Ham et al. (2008)

37

USA 1969–2001

5–18 year olds N = 49,883 (1969) N = 11,774 (2001)

Self-report 1969 National Personal Transportation Survey; 2001 National Household Transportation Survey

Decreased from 42% to 16.2%

↓

McDonald et al. (2011)

38

US 1969–2009

5–14 year olds N = 7416 (1995) N = 11998 (2001) N = 18657 (2009)

Self-report National Personal Transportation Survey in 1969, 1991, 1995, 2001, 2009

Decrease in walk/bike for 5–14 year olds 47.7% to 12.7%

↓

van der Ploeg et al. (2008)

36

NSW, Australia 1971–2003

5–14 years N = 4284 (1971) N = 4936 (1981) N = 662 (1991) N = 816 (1999–2003)

Self-reported Household Travel Surveys

Decrease in ages 5–9 from 57.7% to 25.5% Decrease in ages 10–14 from 44.2% to 21.1% for walking only.

↓

Abbreviations: ↑ = statistically significant increase; ↓ = statistically significant decrease;  = no consistent trend; AT = active transport; OS = organized sport; PE = physical education; SPP = school play period.

declined from 56% to 47% among males but was relatively stable among females (54–51%), between 1995 and 2000.25 No whole sample percentages were provided, therefore the rate of change was −18 percentage points per decade for males and −6 percentage points per decade for females. The questionnaire was restricted to participation in 10 specified sports, which is a limitation as the popularity of these sports may have altered over the study period. The authors suggested that the decline in organized sport may have been due to recent rapid economic growth with an associated increase in household multimedia products. Huhman and colleagues26 surveyed organized sport participation, defined as one or more sessions per week among 9491 students aged 9–13 through the Youth Media Campaign Longitudinal Survey in the USA. Participation was relatively stable over the short time span from 2002 to 2004 to 2006 at 40%, 41% and 42%, with males reporting 39%, 41% and 44%, and females reporting 40%, 41% and 41%. The rate of change for this study was +5 percentage points per decade. Australian trends in organized sport have been investigated in four studies27–30 each consisting of different methods, making it difficult to directly compare. Martin and colleagues27 reported

declines in 10–13 year old South Australians’ participation with 3932 participants, defined as participation in one or more school or club sports in the previous year. Between 1985 and 1997–1999, the proportion declined from 87% to 76% among boys and 80% to 71% among girls, approximately 7% per decade. Another South Australian study found organized sport participation remained stable among 785 9–15 year olds between 1985 and 2004, with a median of one sport in the previous 12 months in both survey years for the total sample, and boys and girls separately.29 A Victorian study found a substantial increase in organized school sport participation between 1985 and 2001, in which 8484 participants reported their participation over the previous week, from 52% to 92% or about +21 percentage points per decade.30 This study also examined organized sport trends in different SES groups; in low SES neighbourhoods, sport participation in at least one sport increased from 26% to 78% and in high SES neighbourhoods it increased from 33% to 67%. The Australian Bureau of Statistics Survey revealed a small but statistically significant increase in participation in at least one organized sport between 2000 and 2003 and 2006 among 5–14 year olds, from 64% to 67% to 68%.28 This demonstrated a rate of change

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Fig. 1. Representation of studies reporting trends in children’s participation in organized sport 1969–2006. 1. Australian Bureau of Statistics28 ; 2. Salmon et al.30 ; 3. Martin et al. 27 ; 4. Eiosdóttir et al.28 ; 5. Huhman et al.26 ; 6. Mak and Day25 ; 7. Scheerder et al.22 .

of +7 percentage points per decade. As the survey was limited to participation in specified selected sports, comparability with other surveys is limited.28 In summary, trends in reported sport are somewhat inconsistent across countries (see Fig. 1), and this may be partly attributable to methodological issues such as differences in questionnaire design, sample age, study period and definition of participation. However, most studies reported an increase in participation or no change, with a decline in participation evident in only one study of Hong Kong children.25 6.2. School physical education Children and adolescents attend schools for an average of 35 h per week, making it a crucial part of their life.31 Physical education has the potential to contribute substantially to recommended levels of MVPA. Wickel and Eisenmann19 found that school PE contributed 12 min of MVPA within a 30 min lesson, measured using accelerometry. Similarly, a study of UK children used telemetry to identify that children and adolescents spend approximately 33% of their PE lesson in MVPA.32 Difficulties in the measurement of school PE possibly limited the number of studies found in this context with available trend data focusing on: the frequency of classes provided; the percentage of students who participate in PE classes; and the MVPA undertaken in class. Studies of trends in school PE participation were identified from the USA, Canada and Australia. In the USA, Lowry and colleagues33 used the Youth Risk Behaviour Surveillance Survey self-report data to reveal a slight increase (49–56%) between 1991 and 2003 in participation in at least one PE class per week among approximately 14,000 high school students. However, the same study identified a decrease in daily PE (5 days per week) between 1991 and 1995 among boys (42–25%) with no change from 1995 to 2003 (25–28%). Similarly, the proportion of girls participating in PE declined between 1991 and 1995 (37–24%), with no change between 1995 and 2003 (24–26%). This equates to an approximate rate of change for participation at least once per week of +6 percentage points per decade. There was no overall change in active

participation (20 min at vigorous intensity, 3–5 times per week) in PE from 1991 (37%) to 1997 (32%) to 2003 (39%).33 A similar study in Canada investigated the same categories of school PE participation over a shorter time span from 1999 to 2005 among 13,260 participants (grades 9–12).34 In contrast to the USA data, Canadian children and adolescents underwent a significant decline in PE on at least one day per week, from 70% to 60%, with more substantial declines among girls (68–55%) than boys (72–65%). This results in a magnitude of change of −16 percentage points per decade for participation in PE at least once per week. A South Australian study of 9–15 year olds reported an increase in PE participation from 1985 to 2004, with a larger magnitude of change among girls.29 The proportion of students in the category of ‘I do not do PE’ fell from 9% to 1% (whole sample), 12% to 1% (girls) and 6% to 1% (boys). A study from Victoria, Australia, found the frequency of PE participation in two or more classes per week decreased from 52% to 22% between 1985 and 2001.30 ‘Once a week PE participation’ increased (35% to 61%), with no significant change in ‘no participation’ (13–17%). In the same study, significant declines occurred for children and adolescents from both low (50–8%) and high SES families (53–31%) in participation in two or more PE sessions per week, with larger declines evident among low SES.30 In the New South Wales Schools Physical Activity and Nutrition Survey (SPANS), school principals reported the time allocated to school PE each week in 2004 and 2010, revealing an increase in primary schools of at least one hour of PE per week. The percentage of secondary schools allocating 80 min or more per week increased from 40% to 51%.31 6.3. Active transport For this review AT was defined as an active mode of transport to and/or from school, such as walking or cycling. AT is a widely studied PA context, perhaps due to its relative ease of recall and its importance as a regular source of PA. Reported mean trip durations of PA range from 6 min per day reported in a US study35 to 20 min per day reported in an Australian study.36 Studies of AT trends were identified from Brazil, Canada, USA, Switzerland, China and Australia (see Fig. 2). Ham and colleagues37

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Fig. 2. Representation of studies reporting trends in schoolchildren’s participation in active transport to and from school 1969–2009. 1. Faulkner et al.34 ; 2. Costa et al.40 ; 3. Grize et al.41 ; 4. Ham et al.37 ; 5. Lewis et al.29 ; 6. McDonald et al.38 ; 7. Salmon et al.30 ; 8. van der Ploeg et al.36 .

used self-report data from 79,719 participants across the 1969 National Personal Transportation Survey and the 2001 National Household Transportation Survey to investigate trends in USA children’s and adolescents’ usual travel mode as reported by parents. A substantial decline from 42% to 16% was found among 5 to 18 year olds who walked or cycled any part of their journey to school.37 The authors suggested that distance between home and school contributed to the decline, with 19% living within a mile in 2001 compared to 35% in 1969. McDonald38 used the same baseline survey to report a decline from 48% to 13% among 5–14 year olds walking and cycling to and from school between 1969 and 2009. From these two large representative studies it appears the approximate rate of change for USA is −9 percentage points per decade. The authors reported another barrier to participation in AT was parental concerns about neighbourhood safety.37 Buliung et al.39 investigated trends in AT (transport mode on the previous day) between 1986 and 2006 among 11–15 year olds from the Greater Toronto Area, Canada. A decline was observed among walking for any part of the school trip across 13,246 participants, from 53% to 43% (ages 11–13) and 39% to 31% (ages 14–15), with a decline in cycling from 2%–1% (whole sample). The approximate rate of change was −5 percentage points per decade. The authors suggested that more flexibility with school bus transport and an increase in car ownership were contributing factors. Active commuting was less common for older adolescents, potentially due to work and extra-curricular commitments after school which required them to transport to locations other than home.39 Active transport among 4168 Brazilian children and adolescents aged 7–15 declined from 49 to 41% between 2002 and 2007.40 As usual mode of travel was assessed in 2002, and previous day’s travel mode in 2007, trends should be interpreted with caution. The magnitude of change for Brazil is larger than for the US and Canada, at −16 percentage points per decade. A study from Switzerland collected data on a single specified day from 4244 participants.41 The percentage of 6–14 year olds who walked or cycled to and from school was relatively high, but decreased between 1994, 2000 and 2005 from 78% to 72% to 71%, respectively. Interestingly, the percentage who walked remained fairly stable (57% to 55% to 54%), while the percentage

who cycled significantly decreased over this time period (21% to 17% to 16%). The approximate magnitude of change for Switzerland is −6 percentage points per decade. The authors commented that it is customary for Swiss children to attend their local government school, an average of 2.4 km from home, making it more conducive for AT. Further, parents indicated safety was not a high concern, in contrast with studies from USA and Australia.41 Cui et al.42 investigated commuting to and from school in nine Chinese provinces including a total of 6935 students. A self-report questionnaire conducted in 1997, 2000, 2004 and 2006 identified that the percentage of students who walked or cycled significantly decreased from 98% to 88% (ages 6–12) and from 93% to 83% (ages 13–18). The approximate magnitude of change for China is −11% percentage points per decade for both age groups. This study also collected demographic data and found the primary reason for the decrease in active commuting was the increase in distance from home to school possibly due to a decline in the number of schools over this time period.42 Australian studies have reported general declines in AT in recent decades. In New South Wales, AT declined between 1971 and 2003 among 10,698 participants from 58% to 26% (5–9 year olds) and 44% to 21% (10–14 year olds).36 The rate of change for walking was approximately −9 percentage points per decade. Similar to other studies, there was an increase in the percentage driven to school, by 44% in 5–9 year olds and 36% among 10–14 year olds.36 A Victorian study reported a significant decline in regular walking to school (6–10 times per week) among 7–15 year olds from 37% in 1985 to 26% in 2001.30 Cycling to and from school declined from 20% to 8% across the same time period, a rate of change for both walking and cycling of −7 percentage points per decade. This study also examined AT trends in different SES groups; in low SES neighbourhoods, walking to school increased from 29% to 32%, while cycling declined from 24% to 6%. In contrast, walking in high SES neighbourhoods declined from 40% to 22%, and cycling declined from 18% to 10%. Salmon and colleagues30 suggested that the distance between home and school was a factor as low SES students often attend local schools making it easier for them to actively commute whereas high SES students may travel further to attend high SES schools.

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A South Australian study investigated travel mode over the previous week in children aged 9–15 years using the same measure in 1985 and 2004.29 A substantial decline occurred in cycling, from 21% to 5% (whole sample), 27% to 9% (girls) and 13% to 2% (boys). Walking to and from school remained relatively stable among the whole sample from 40% to 37%, and among girls (44–42%) and boys (37–32%) separately. This equates to a rate of change of −8 percentage points per decade for cycling and −2 percentage points per decade for walking. It is evident from these three studies, that there has been an overall decline in walking and cycling to school in Australia, with approximate rates of decline ranging from −5 to −9 percentage points. Other countries have displayed rates of change ranging from −5 percentage points in Canada to −16 percentage points in Brazil. Despite methodological differences between the studies, all show that within various developed countries and the one developing country (Brazil) a decline has occurred in AT with more substantial declines in cycling. Some of this decline is likely due to increases in car ownership and increases in distance from school to home. 6.4. Physical activity during school play periods Stanley et al.43 estimated that 65% of the 20 most popular lunchtime activities contributed to MVPA among Australian children.43 In a UK study of 8 year olds, boys accumulated 28 min of MVPA (±11) and girls 21 min of MVPA (±8) during the lunch break.44 Even though these studies were conducted in different locations and used different methodologies, they demonstrated that children and adolescents can achieve up to 50% of their daily PA requirements in school play periods alone. Thus, school play periods provide an ideal opportunity for the accumulation of MVPA. There are few studies that have investigated trends in PA and sedentary behaviour in children and adolescents during school play periods, highlighting a need for further research. Using selfreport measures a South Australian study29 found an increase in sedentary behaviour between 1985 and 2004. The percentage of 9–15 year olds reporting ‘sit and talk’ activity during lunchtime increased across the whole sample from 17% to 35%, and among boys from 21% to 34% and girls from 12% to 35%. Declines in the percentage of girls who ‘run around’ during lunchtime (61–46%) were sharper than those for boys (48–46%). Across the whole sample this equates to a rate of change of -4 percentage points per decade in the percentage that report ‘run around’ during lunchtime (54–46%). Recent advances in objective measurement of PA have paved the way for more accurate monitoring during school play periods, and the paucity of evidence for trends in this important context highlights the need for valid baseline data from which trends can be confidently monitored. 7. Discussion A previous review of the literature2 identified a decline in the structured contexts of AT, PE and organized sport. This review concludes that AT is still declining within the countries studied with increased distances between home and school and increased reliance on motorized transport implicated in these trends. Safety reasons were also highlighted as potential deterrents to active commuting. There are mixed results for organized sport, with some studies identifying decreases, but most reporting no change or an increase in participation. For PE participation and PA during school play periods there is very little generalizable evidence upon which to draw conclusions. While the findings from this review should be observed with caution due to limitations when comparing studies that used different methodological approaches, including question

structure, timeframe and definition of context, there is little evidence for the popular view that children’s and adolescents’ PA is in general decline. 8. Conclusion Together, the observations in this review highlight the need for internationally agreed instruments for context-specific measurement of PA in young people to facilitate international comparisons and to direct the collective resources of the global research community towards improving PA promotion in this population. Acknowledgement There was no external financial assistance with this project. References 1. Johnson R, Russ J, Goran M. Physical activity related energy expenditure in children by doubly labeled water as compared with the Caltrac accelerometer. Int J Obes 1998; 22:1046–1052. 2. Dollman J, Norton K, Norton L. Evidence for secular trends in children’s physical activity behaviour. Br J Sports Med 2005; 39(12):892–897. 3. World Health Organization. Global Recommendations on Physical Activity for Health, 2012, 2011: 5–17 year olds. Available at: http://www.who.int/ dietphysicalactivity/physical-activity-recommendations-5-17years.pdf%3E. Accessed 12 August 2012. 4. Martin K, Rosenberg M, Miller M et al. Move and munch final report, In: Trends in physical activity, nutrition and body size in Western Australian children and adolescents: the Child and Adolescent Physical Activity and Nutrition Survey (CAPANS) 2008., 2008. 5. Tudor-Locke C, Pangrazi RP, Corbin CB et al. BMI-referenced standards for recommended pedometer-determined steps/day in children. Prev Med 2004; 38(6):857–864. 6. Centres for Disease Control and Prevention. Youth risk behaviour surveillance – United States, 2011. MMWR 2012; 61(4). 7. Townsend N, Bhatnagar P, Wickramasinghe K et al. Physical activity statistics 2012, London, British Heart Foundation, 2012. 8. Saltó MJC. Percentage of physically active children and adolescents, Spain, World Health Organization Europe, 2009. 9. Reddy SP, James S, Sewpaul R et al. Umthente Uhlaba Usamila – The South African youth risk behaviour survey, 2008, Cape Town, South African Medical Research Council, 2010. 10. Sports Science Institute of South Africa. Healthy active kids South Africa report card 2010, South Africa, Sports Science Institute of South Africa, 2010. 11. Rodriguez MDP, Colley R, Jimenez JA et al. The Mexican report card on physical activity for children and youth 2012, Mexico, Canada and Mexico Battling Childhood Obesity, 2012. 12. Onywera V, Tremblay M, Colley R et al. Kenya’s 2011 report card on the physical activity and body weight of children and youth, Kenya, Healthy Active Kids Kenya, 2011. 13. LeBlanc AG, Janssen I. Difference between self-reported and accelerometer measured moderate-to-vigorous physical activity in youth. Pediatr Exerc Sci 2010; 22:523–534. 14. Knuth A, Hallal PC. Temporal trends in physical activity: a systematic review. J Phys Act Health 2009; 6:548–559. 15. Ekelund U, Tomkinson G, Armstrong N. What proportion of youth are physically active? Measurement issues, levels and recent time trends. Br J Sports Med 2011; 45(11):859–865. 16. Møller N, Kristensen PL, Wedderkopp N et al. Objectively measured habitual physical activity in 1997/1998 vs 2003/2004 in Danish children: the European Youth Heart Study. Scand J Med Sci Sports 2009; 19:19–29. 17. Raustorp A, Ekroth Y. Eight-year secular trends of pedometer-determined physical activity in young swedish adolescents. J Phys Act Health 2010; 7:369–374. 18. Sigmundová D, El Ansari W, Sigmund E et al. Secular trends: a ten-year comparison of the amount and type of physical activity and inactivity of random samples of adolescents in the Czech Republic. BMC Public Health 2011; 11(1):1–12. 19. Wickel EE, Eisenmann JC. Contribution of youth sport to total daily physical activity among 6- to 12-yr-old boys. Med Sci Sports Exerc 2007; 39(9):1493–1500. 20. Olds T, Dollman J, Maher C. Adolescent sport in Australia: who, when, where and what? ACHPER Healthy Lifestyles J 2009; 56(1):11–16. 21. Guagliano JM, Rosenkranz RR, Kolt GS. Girls’ physical activity levels during organized sports in Australia. Med Sci Sports Exer 2013; 45(1):116–122. 22. Scheerder J, Vanreusel B, Taks M et al. Social stratification patterns in adolescents’ active sports participation behaviour: a time trend analysis 1969–1999. Eur Phys Educ Rev 2005; 11(1):5–27. 23. Telama R, Laakso L, Nupponen H et al. Secular trends in youth physical activity and parents’ socioeconomic status from 1977 to 2005. Pediatr Exer Sci 2009; 21(4):462–474.

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