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1 Introduction H ealth is influenced by many factors, genetic, behavioral, and envi- ronmental, that are present prior to conception and continue throughout an individual's life span. Since childhood health pre- dicts adult morbidity and mortality, it is beneficial to attain, sustain, and monitor health from childhood to adulthood. The United States and other countries have designed programs to measure or improve the health of the population in many different domains, including physical fitness, and at all ages. Key to setting national health agendas and priorities, as well as goals for individuals, is having goals for public health, metrics with which to determine health reliably and accurately in various areas, and an under- standing of how close the population or individuals are to the established goals. Examples of surveillance programs designed to measure health in vari- ous dimensions in the United States are the National Health Interview Sur- vey (NHIS), the National Immunization Survey (NIS), the Behavioral Risk Factor Surveillance System (BRFSS), the National Health and Nutrition Examination Survey (NHANES), and the National Youth Physical Activity and Nutrition Study, to name a few. In addition to such national surveys, states may conduct their own surveys to track health status. Health pro- grams can be established in the school environment or be part of the school curriculum (e.g., physical education classes), with the purpose of improving or evaluating health status among youth. While surveys of physical activity among youth have been carried out in recent years, however, national fit- ness surveys have not been conducted since the 1980s (see Chapter 2). The 15
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16 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH NHANES includes components pertinent to physical fitness and a 2012 NHANES Youth Fitness Survey is currently under way. As discussed in Chapter 2, there have been many efforts to identify fitness tests and standardize a battery of such tests for youth. To this day, however, an array of tests continues to be used, selected based on various historical circumstances and understandings of the science. This report rep- resents an effort to provide an evidence-based approach to selecting field- based fitness measures for youth for inclusion in a national fitness survey. Recommendations for tests to be used in schools and other educational settings are provided as well. BACKGROUND To better understand the content of this report, it is important to dis- tinguish between physical fitness and physical activity. Physical fitness has been defined as "a set of attributes that people have or achieve that relates to the ability to perform physical activity" (HHS, 1996, p. 21). The focus of this report is on the potential health-related components of physical fitness: body composition, cardiorespiratory endurance, musculoskeletal fitness, and flexibility. Physical activity, on the other hand, is defined as "any body movement produced by muscle action that increases energy expenditure" (Castillo-Garzon et al., 2006, p. 213). There are many types of physical activities, such as exercise (physical activity with the purpose of improving fitness), sports, dance, and recreational activities. Box 1-1 and Appendix B provide the committee's operational definitions of physical fitness and other terms used throughout the report. Fitness tests are conducted for several purposes for both individuals (e.g., goal setting, planning for improvement, preparing for specific tasks) and society at large (e.g., assessing current fitness status, tracking changes, research). The ultimate purpose, however, is to improve the health and physical performance of individuals, as well as the population as a whole. As noted above and described in detail later in this report, fitness surveys have been conducted in the United States at both the national and state levels. Similarly, other countries have developed fitness test batteries and conducted national surveys (see Chapter 2). Early national fitness tests included items commonly described as skill- related fitness, as well as items focused on health-related fitness. Since the first national fitness test was developed in 1958, appropriate items for inclusion in fitness test batteries have been the subject of debate. The first national health- related physical fitness test was developed in 1980 (AAHPERD, 1980), and since then there has been increased emphasis on defining the relationship of fitness items to health. While measures of performance-related fitness are designed to evaluate a person's capability to carry out certain physical tasks
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INTRODUCTION 17 BOX 1-1 Terms Used in This Report Body composition: the components that make up body weight, includ- ing fat, muscle, and bone content. Cardiorespiratory endurance: the ability to perform large-muscle, whole-body exercise at moderate to high intensities for extended periods of time (also referred to as aerobic fitness or aerobic capacity) (Saltin, 1973). Criterion-referenced standards (criterion measures): evaluation stan- dards used to interpret physical fitness test scores and provide informa- tion about a participant's health status. Cut-point (cutoff score): a test score that represents the minimum level of performance that must be achieved for a participant to be said to be at reduced risk or fit/healthy. Flexibility: "the intrinsic property of body tissues that determines the range of motion achievable without injury at a joint or group of joints" (Holt et al., 1996, p. 172). Musculoskeletal fitness: a theoretical construct reflecting the inte- grated function of an individual's muscle strength, endurance, and power to enable the performance of work against one's own body weight or an external resistance. Physical activity: "any body movement produced by muscle action that increases energy expenditure" (Castillo-Garzon et al., 2006, p. 213). Physical fitness: "a set of attributes that people have or achieve that relates to the ability to perform physical activity" (HHS, 1996, p. 21). Reliability: the dependability of test scores, their freedom from error, and their reproducibility in repeated trials on the same individual. Validity: the extent to which a test measures what it is designed to measure; the degree to which evidence supports the interpretation of test scores (Eignor, 2001). or activities, the focus of health-related fitness testing is on concurrent or future health status. The measurement of health-related fitness in youth is the focus of this report. As more sophisticated research and statistical meth- ods, computer technologies, and data management systems have emerged, the link between fitness tests and health has been more firmly established. Nevertheless, there is more to be done. This report is based on a systematic review of the literature designed to answer key questions concerning fitness and health in youth.
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18 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH STATEMENT OF TASK This study was undertaken to identify measures of fitness for which there is evidence of an association with health outcomes and to provide guidance for interpreting fitness test scores (e.g., setting health-related cut- points for specific tests). The committee was asked to be attentive to the practicality of the recommended tests and to discuss considerations and pros and cons for these tests. The specific questions posed in the commit- tee's statement of task are shown in Box 1-2. METHODS An 11-member committee was convened to answer the questions posed in the statement of task shown above. The committee members had exten- sive expertise in fitness and physical activity and were selected specifically for their knowledge of youth health issues, body composition and matura- tion, and motor coordination; methodologies for developing fitness mea- sures related to health; physical education, physical activity, and fitness in schools; and national fitness surveys. Many committee members also are familiar with the various fitness test batteries that have been used through- out history and in different countries and that have responded to specific situations and purposes. Committee members are knowledgeable as well about the many factors (e.g., demographic characteristics) that interact with youth performance on tests for the various fitness components. Because the statement of task also requested that the committee be mindful of practical considerations when selecting fitness tests for use in the field, many of the committee members have practical experience with implementing fitness test batteries. In addition to its members' extensive knowledge of fitness and health, the committee drew on other sources to inform its decisions about the selection of fitness test items. A major resource for inferring relevant asso- ciations between specific fitness test items and health markers in youth was a systematic review of the peer-reviewed scientific literature, designed and conducted by the Centers for Disease Control and Prevention (CDC) and encompassing the period 2000-2010. Further detail on the conduct of this review is presented in Chapter 3. For two fitness components--cardio respiratory endurance and musculoskeletal fitness--the committee received the results of the review in the form of abstracted tables along with the full articles, and then selected the articles to review in depth based on its assessment of the quality of the research. Although articles on flexibility were not coded separately in the literature review, the committee reviewed several studies focused on the other fitness components that included a flex- ibility measure. A systematic review of the literature with respect to body
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INTRODUCTION 19 BOX 1-2 Statement of Task An ad hoc committee will recommend physical fitness test items for assessment of youth fitness components that are associated with health outcomes. The recommended items will be suitable for inclusion in a national survey of fitness in children and youth. The committee will make use of a systematic review of the literature conducted by the Centers for Disease Control and Prevention. In examining the review, the commit- tee will evaluate the relationships between the fitness components and health outcomes (e.g., cardiovascular disease risk factors, musculosk- eletal health, diabetes, obesity and others). Further, for selected fitness components the committee will examine the relationships between per- formance on specific test items and health outcomes. In addition to the primary task above, the committee will answer the following questions: 1.For recommended test items for which there is evidence of an association with health, how should performance for the test items be interpreted? Should the interpretation be based on a cut-point approach? Are there alternative approaches to interpret performance? 2.If the association between a particular test and health outcomes reveals no obvious relationship to health, what strategy is most appropriate for identifying a criterion-referenced standard? In such a case, the committee may consider the use of norm-referenced standards. 3.How do demographic characteristics and overweight and obesity affect the tests scores and subsequent evaluations? 4.What additional research is needed to augment the evidence (or lack thereof) about the associations between fitness measures and health outcomes? The committee will also study to what extent is change in perfor- mance on a fitness test item (e.g., handgrip strength or 1.5-mile walk/run) associated with change in health outcomes in youth who are apparently "healthy" but include both obese and nonobese. In addition, the com- mittee will identify the strengths and weaknesses of fitness test items in regards to their practicality and as indicators of health outcomes in a school setting and, based on practicality, will provide recommendations for the most appropriate measures for each fitness component.
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20 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH composition also was not conducted because, even though this component is frequently included in fitness test batteries, its relationship to health is well known. Although the committee did not participate in the design of the literature review, members had ample opportunities to interact with the CDC in order to understand the nature of the review. The CDC literature review also did not include integrity and feasibility studies. The commit- tee conducted further literature searches and reviews in other areas, for example, to assess the integrity of specific fitness tests or to complement the CDC's systematic review. In addition, the committee drew on the work and experience of other organizations and countries to the extent that this information is available to the public. The committee also benefited from expert presentations dur- ing an open session on November 15-16, 2011; the agenda for this open session is in Appendix A. Presenters had extensive experience in the devel- opment of fitness test batteries and in the associations of fitness with meta- bolic risk factors and body composition. Other presenters had experience in implementing and interpreting results of a battery of fitness tests in the field, providing the committee with insight into feasibility considerations and challenges encountered at the time of test implementation. The main purpose of this report is to identify fitness measures that are associated with health markers in youth and that are also practical in a field setting. To accomplish this purpose, the committee agreed on various concepts and on a general conceptual framework that guided its decisions. Before reviewing the literature, the committee decided on a stepwise pro- cess for identifying the best test items for each fitness component. As will be obvious from the description in Chapter 3, the literature review was designed to provide information about potential associations of fitness tests with health markers (or risk factors) and outcomes in youth as opposed to those that might be seen later in life. For that reason, the majority of health issues explored during the review were health markers (or risk factors) for a disease and not health outcomes per se, as most health conditions or diseases do not manifest until adulthood. As is clear from the discussion throughout the report, studies that follow youth into adulthood are infre- quent. Since the 1980s, moreover, organizations and relevant government agencies have focused their efforts on the health benefits of physical activity among youth rather than on fitness, which was the focus prior to the 1980s. The lack of a recent focus on fitness has resulted in a less than ideal scien- tific literature base addressing questions of fitness and health. Nevertheless, the knowledge base has increased sufficiently to support the conduct of a national fitness survey. The focus on health in youth is a unique feature of this report and one that presented many challenges given the inadequate amount and nature of the relevant literature. However, this focus is in tune with current thinking that factors related to health in adults cannot neces-
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INTRODUCTION 21 sarily be extrapolated to youth, and therefore, health markers in youth need to be defined and reviewed. While the committee provides guidance for developing cut-points (cut- off scores) for and interpreting performance on fitness tests, it did not develop specific cut-points for the recommended test items. Rather, the committee suggests an ideal approach to establishing cut-points. Recogniz- ing that all the data necessary to establish cut-points do not exist for all the recommended tests, the committee also provides alternative approaches for establishing interim cut-points when such data are unavailable. In addition, there are aspects of fitness testing that the committee did not address in depth, such as protocols for the recommended tests, specific training for test administrators, or the appropriateness of fitness components that were not included in the committee's statement of task. Finally, the studies reviewed were designed to collect evidence on the relationship between fitness tests and health in healthy youth. Studies on overweight and obese youth were included in the review; however, studies in special populations, such as ath- letes or people with disabilities1 or congenital diseases, were not reviewed. Therefore, the committee's findings, conclusions, and recommendations do not target those special populations. ORGANIZATION OF THE REPORT This report is organized into chapters dedicated to background on measuring fitness in youth; the committee's methodology; and its findings, conclusions, and recommendations. Chapter 2 provides a historical per- spective on the origins of youth fitness testing and the changes that have occurred over the years both in the tests and in their uses. This chapter includes a table describing fitness test batteries currently used around the world. Chapter 3 describes in detail the methodology used by the commit- tee to identify test items, including the CDC's systematic review, which was the primary basis for the committee's conclusions and recommendations. Chapters 4, 5, 6, and 7 present the committee's rationale for recommending test items for the four fitness components, respectively--body composition, cardiorespiratory endurance, musculoskeletal fitness, and flexibility--high- lighting the findings of the scientific literature. As noted earlier in this chap- ter, the primary purpose of this report was to make recommendations for a national survey. A secondary purpose was to make recommendations for 1A disability is defined as any restriction or lack of ability to perform an activity in the man- ner or within the range considered normal for a human being. For the purposes of this report, this term should be construed in the broadest sense, covering impairments (i.e., a problem in body function or structure), activity limitations (i.e., a difficulty encountered by an individual in executing a task or action), and participation restrictions (i.e., a problem experienced by an individual in involvement in life situations).
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22 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH the use of fitness tests in schools and other educational settings.2 Because tests vary based on their potential uses, separate chapters were prepared for each of these two uses of fitness test items. Chapter 8 presents the com- mittee's recommendations for national surveys of youth fitness. Chapter 9 describes the importance of fitness in the context of education, details factors to consider when implementing fitness tests in schools and other educational settings, and presents the committee's recommendations for specific fitness tests for educational settings. Finally, Chapter 10 includes the committee's recommendations for future research. REFERENCES AAHPERD (American Alliance for Health, Physical Education, Recreation and Dance). 1980. Health related physical fitness test manual. Reston, VA: AAHPERD. Castillo-Garzon, M. J., J. R. Ruiz, F. B. Ortega, and A. Gutierrez. 2006. Anti-aging therapy through fitness enhancement. Clinical Interventions in Aging 1(3):213-220. Eignor, D. R. 2001. Standards for the development and use of tests: The standards for educational and psychological testing. European Journal of Psychological Assessment 17(3):157-163. HHS (U.S. Department of Health and Human Services). 1996. Physical activity and health: A report of the Surgeon General. Atlanta, GA: HHS, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion. Holt, J., L. E. Holt, and T. W. Pelham. 1996. Flexibility redefined. In Biomechanics in sports XIII, edited by T. Bauer. Thunder Bay, Ontario: Lakehead University. Pp. 170-174. Saltin, B. 1973. Oxygen transport by the circulatory system during exercise in man. In Lim- iting factors of physical performance, edited by J. Keul. Stuttgart, Germany: Thieme Publishers. Pp. 235-252. 2Other educational settings include, for example, gymnasiums and fitness centers.