Physical Activity InterventionsEffects of physical activity interventions in youth: Review and synthesis
Introduction
The impact of behavior on health, with a special emphasis on children through young adults, is a central focus for the prevention agenda in the United States1, 2 and health policy internationally.3, 4, 5 Physical inactivity has been identified as an independent risk factor for coronary heart disease (CHD) with the risk for CHD increased nearly twofold for persons who are physically inactive.6 Reports have attributed 22%–30% of cardiovascular deaths, 20%–60% of cancer deaths, and 30% of diabetes deaths to sedentary lifestyles and dietary factors.7 Tobacco use was the only more prominent behavioral contributor to mortality than physical inactivity and diet. Major reviews by Blair et al.8 and Pate et al.9 also identified physical inactivity as a serious problem and major public health concern for youth and adults.
During the 1990s there were a number of major conferences and reports that addressed physical activity. Some of these were the National Heart, Lung, and Blood Institute (NHLBI) workshop on Physical Activity and Cardiovascular Health: Special Emphasis on Women and Youth in 199110; the International Consensus Conference on Physical Activity Guidelines for Adolescents, in 199411; National Institutes of Health (NIH) Consensus Conference on Physical Activity in 199512; the Surgeon General’s Report on Physical Activity and Health in 199613; the first Centers for Disease Control and Prevention (CDC) Guidelines for School and Community Programs to Promote Lifelong Physical Activity Among Young People in 199714; and the National Association for Sport and Physical Education (NASPE) Physical Activity for Children: A Statement of Guidelines in 1998.15 These conferences and reports stressed the importance of focusing on children and adolescents by establishing infrastructures in schools and communities to promote healthy physical activity patterns. In addition, several international reports were released including, the World Health Organization’s Global School Health Initiative16 and the Young and Active report.5 This latter report is a public health policy framework designed to maximize the opportunity for young British people to participate in a lifetime of regular health-enhancing physical activities.
Although the findings reported in the literature are not directly comparable, it is possible to develop an approximate estimate of the proportion of young people who are adequately active, trends across age, and differences between boys and girls. A study conducted in Austria, England, Finland, and Norway reported that 61% of 11 year olds and 50% of 15 year olds participated in one to six sessions per week of vigorous activity outside of school.17 In comparison, a study of 6,500 Welsh 11 to 16 year olds found that less than 49% of the boys and 19% of girls engaged in vigorous activity for at least 30 minutes, three or more times per week.18, 19 The authors also reported that participation declined significantly with age. A survey of Italian girls aged 14 to 18 years found that only 6% to 10% regularly took part in sports or cycled regularly and that 60% to 70% reported no leisure-time physical activity.20
A national survey of Australian children and youth (aged 9 to 15 years) included a question on whether or not students were vigorously active three to four times per week for at least 30 minutes per session.21 The study found that 50% of boys and 39% of girls were active at this level and that there was no apparent decline with age for either boys or girls. In another European survey, the Berlin-Bremen Study of Health Behavior in Childhood and Adolescence examined the frequency and duration of participation in vigorous and moderate activities among 932 seventh- and eighth-grade students.22 They found that approximately 18% of students spent less than 30 minutes per week engaged in vigorous activity and approximately 30% spent 30 to 120 minutes per week in vigorous activities.
Armstrong and his colleagues assessed physical activity participation among 266 English children aged 11 to 16 years by monitoring heart rate on three school days and one Saturday.23 They found that 23% of boys and 12% of girls had at least one 20-minute period of elevated heart rate over three school days and that 4% of boys and less than 1% of girls had three 20-minute periods of elevated heart rate on three school days. They also noted that girls are less active than same-aged boys and that there was a greater decline in physical activity participation across high school years among girls.
The Canada Fitness Survey of 1981 involved 23,000 respondents aged seven years and older.24 Based on the criterion of three hours per week of physical activities of at least four METS intensity, approximately 75% of young people were sufficiently active. However, when the criterion of participation in vigorous activity for three hours per week was applied, less than 5% of children and youth were sufficiently active. Finally, the U.S. National Youth Risk Behavior Survey conducted in 1990 assessed more than 11,000 students in grades 9 to 12.25 It was found that 50% of all boys met the criterion and that the proportion who were active did not vary by school year when the criterion of vigorous activity for at least 20 minutes on at least three days per week was used. In contrast, the proportion of girls who were active varied from 31% in grade 9 to 17% in grade 12.
Overall, despite the many methodologic differences in international surveys of youth physical activity, three consistent and general findings have emerged. First, a substantial proportion of children and adolescents are not sufficiently active; most surveys found less than 50% of adolescents were sufficiently active. Second, a considerably smaller proportion of girls than boys were sufficiently active. Third, activity participation declines with age during adolescence, although it is not clear at what age the decline commences and if the rate of decline is linear. There is a need worldwide to address gender differences in designing interventions especially beginning in middle school. Few of the studies (especially in the United States) addressed the gender issue to the extent needed or reported results separately for males and females. In addition, high-risk groups have many needs requiring special attention; these needs may be related to income, education, transportation, and cultural considerations.
Although the concept of risk factor tracking is well established,26 a fairly recent concept is that behavioral risk factors also track and that they tend to cluster in health-promoting or health-compromising directions. Of the limited research findings reported, physical activity or inactivity tends to track during early childhood and less-active children tend to remain less active than the majority of their peers.27 Another preschool study examined the effects of physical activity on the change in body fatness from preschool to first grade and reported that children with low activity levels gained substantially more subcutaneous fat than did more-active children. This study followed children from preschool into adolescence and found that physical activity and sedentary behaviors track and that girls were already less active than boys in early elementary grades.28 The Studies of Children’s Activity and Nutrition (SCAN) longitudinal cohort research in 8 cities across the United States were conducted to advance measurement methodology to use with 3 and 4 year olds at baseline and to examine the determinants of eating and physical activity behavior.27 Several of the SCAN cohorts are still being measured as adolescents.28, 29
Since physical activity health behaviors track into adulthood,30, 31, 32, 33 it is important to review the evidence-based findings in school and community settings34 for designing and implementing effective policy and programs to promote physical activity in young people.35, 36 The purpose of this paper is to review and synthesize the findings of studies testing interventions to increase physical activity in schools and other community settings for children through young adulthood. The completed studies are categorized by the following age groups: preschool, elementary, middle and high school, and college. In addition, review tables also are included for the school and community studies completed or currently in progress. Implications for future research, policy, and practice are addressed.
Section snippets
Identification of studies
Studies from 1980 to 1997 were identified using Medline search through both MeSH heading and textwords. In addition, bibliographies from prior review articles, published studies, and recommendations from national and international colleagues were used. Only published articles in refereed journals and manuscripts accepted for publication were considered for the completed studies.
Criteria for inclusion/exclusion
The following criteria were used for including studies in this review: (1) quantitative assessment of physical
Results
A total of 14 completed school-based studies met the inclusion criteria. Of these, 11 were U.S.65, 67, 68, 71, 72, 73, 74, 75, 76, 77, 78 and 3 were foreign studies.79, 80, 81 There are eight studies in progress in the United States (Table 2). One of these has published the design paper.82 There are fewer studies in community settings than in schools. A total of 3 community studies in the United States are listed in Table 3, 83, 84, 85 and 4 studies in progress86, 87, 88 are displayed in Table 4
Synthesis of school-based studies
As shown in Table 1, Table 2, there was a total of 22 school-based studies with 14 completed and 5 in progress. One study each was conducted in Norway, in Wales, and in Australia. The rest were carried out in the United States. The 8 studies in-progress are all in the United States. Numerous foreign studies have been conducted; however, most used fitness measures and did not report physical activity findings.
No studies with a physical activity measure were identified for students below grade 3.
Synthesis of community-based studies
As shown in Table 3, Table 4, only 7 studies were identified in the community setting that included physical activity measures. All of these were in the United States, with 3 completed and 4 currently underway. This group of studies is similar to the school setting in that no studies involving children in preschools, kindergarten, or early elementary grades were found. In addition, there were no studies of college-aged groups. The completed studies involving upper elementary-aged students and
Research design issues
The designs and analytical strategies used in the more recent studies include more randomized trials, involve multicomponent interventions, and often address measurement of multiple behaviors and environmental changes. The absence of preschool and early primary grade studies appears to be due partially to the difficulty in measuring physical activity as well as delivering interventions. Multicomponent coordinated studies and programs usually are based on several theoretical models.
The majority
Recommendations for research
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Develop more reliable and valid self-report measures of physical activity for different developmental age groups as well as more use of observations and objective measures in conjunction with self-report measures.
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Conduct more studies on increasing out-of-school activity levels.
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Conduct studies on the effectiveness of interventions to prevent the decline in physical activity in females and adolescents.
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Conduct studies on the effectiveness of intervention approaches for diverse ethnic/racial
Recommendations for public health practice
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Establish school policies and environments to provide space, equipment, and supervision for before and after school and lunch and recess periods to promote physical activity.
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Provide appropriate resources for more emphasis on mastery of fundamental skills in children, since these are essential for exercising choices for leisure-time activities across the lifespan.
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Introduce more intramural and extramural activities that direct more resources to programs that service all students.
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Promote more
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