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Summary P hysical fitness is a state of being that reflects a person's ability to perform specific exercises or functions, and is related to present and future health outcomes. In the United States, serious efforts to assess the physical fitness of youth with a battery of tests began in the 19th cen- tury. These efforts intensified during times of war, focused primarily on improving athletic performance and military preparedness. Over time, the focus of such surveys shifted to assessing health rather than performance, reflecting growing concern about the current and future health of the nation's youth. While measures of performance-related fitness are designed to evaluate a person's capability to carry out certain physical tasks or activi- ties, the focus of health-related fitness testing is on the concurrent or future health status of the subject under assessment. The first U.S. national survey of youth fitness in 1958 was followed by surveys in 1965 and 1975 and then in 1985-1986. States and schools have continued to assess fitness in youth during the past two decades; after the 1985-1986 survey, however, there was no national-level assessment of youth fitness until 2012, as part of the National Health and Nutrition Examination Survey. Several factors may account for this gap, including the fact that interest and effort have been directed more toward understanding the role of physical activity in youth. This shift and the challenges inherent in associating fitness in youth with health have resulted in few advances in our understanding of the physiology and outcomes of fitness. Assessment of fitness historically has encompassed such components as body composition, cardiorespiratory endurance, musculoskeletal strength and endurance, and flexibility. Examples of tests used historically in national 1
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2 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH surveys and schools are the progressive shuttle run and mile run tests for cardiovascular endurance, measurement of body mass index (BMI) for assessment of body composition, the curl-up and push-up tests for muscular endurance, and the sit-and-reach tests for flexibility. While the components of fitness measured and the specific test items included in protocols have varied considerably across test batteries and over time, youth fitness testing has become a well-established institution in school physical education programs during the past half-century. In a school context, tests are being used as institutional fitness assessment tools, as educational tools to teach youth and their families about the importance of physical fitness, and as communication tools to guide individuals on attainable goals for maintaining fitness and health. These efforts are costly in terms of not only human capacity and financial resources, but also the extensive training and organizational and communication skills required for their implementation. Most important, it is essential to use appropriate tests and understand the results in a health context to minimize misclassification and stigmatization of youth. Selection of the best tests is therefore a crucial process, and knowledge gaps in this area were an important motivator of the present study. This study was undertaken in light of the past challenges encountered in identifying fitness tests related to health in youth, spurred by a renewed interest in fitness as one of the key tenets of health. STUDY APPROACH Given the gaps in knowledge noted above, the Institute of Medicine (IOM) convened an 11-member committee with expertise in fitness mea- sures, body composition and maturity, physical activity, physical education, the development of cut-points (cutoff scores), motor development and skill, and modifiers of fitness to conduct this study. The committee was asked to assess the relationships between fitness tests and health outcomes in youth based on a review of the literature designed and conducted by the Centers for Disease Control and Prevention (CDC) (the committee's statement of task is shown in Box S-1). The CDC search criteria included longitudinal, experimental study designs in which fitness and health were measured in healthy1 children aged 5-18 during 2000-2010. The CDC searches were conducted specifically for the fitness components cardiorespiratory endur- 1The criteria included overweight and obese youth, but excluded youth with various dis- abilities or congenital diseases. Since the primary task for this study was to identify fitness tests appropriate for a national youth fitness survey of the general youth population, the commit- tee did not review additional literature specific to populations with disabilities, such as those with cognitive or physical impairments, activity limitations, or participation restrictions (as defined in Appendix B).
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SUMMARY 3 BOX S-1 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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4 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH ance and musculoskeletal strength and endurance. The relationship of body composition measures to health is well established, so a systematic review of their relationship to health was not conducted. Although time and resources did not allow for a systematic review of the flexibility com- ponent, the committee evaluated the relationships between flexibility and health outcomes in studies from the CDC review that included a flexibility measure. To guide its review and deliberations, the committee created a concep- tual framework that depicts the potential relationships between physical fitness components and health as they are modified by various factors, such as demographic characteristics, maturity status, motor skills, and genetics. In addition to this conceptual framework, the committee developed the follow- ing set of general criteria for selecting tests to be implemented in the field: · identification of a relationship between a fitness component and health markers; · evaluation of the quality of the studies and the strength of the evidence for a relationship between fitness test items and health markers in youth, based on the CDC's systematic review; · identification of health-related test items; · evaluation of the integrity of test items (i.e., validity and reliability); and · evaluation of the feasibility of implementing test items. In its statement of task, the committee was asked not only to select test items for a national fitness survey but also to consider the practicality of their implementation. The committee reviewed only the evidence for field-based methods because, even if they are more prone to error than laboratory methods, they require less highly specialized training and are conducted with mobile equipment, adequate for assessing large samples of youth. The committee also recognized that national surveys and schools and other educational settings2 raise different implementation issues. In addition, the conduct of fitness tests in schools may be driven by goals beyond health, such as educating about the importance of specific fitness components. Because of their role as educational tools, certain test items will be beneficial in a school fitness test battery even if their relationship to health cannot as yet be confirmed in youth. Therefore, the committee developed separate sets of recommendations for these two settings. Implementing the best health-related fitness items entails important steps that relate to the interpretation and communication of the test results in a health context. Identifying one or more health outcomes that are 2Other educational settings include, for example, gymnasiums and fitness centers.
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SUMMARY 5 related to the test items of interest, then, is essential. Equally important is understanding the relationship between the test items and the associated health outcomes in quantitative terms so the results can be interpreted in a health context. For this purpose, a criterion-referenced cut-point--a test performance score below (or above) which a risk to health may exist--can be used. Ideally, criterion-referenced cut-points would be derived from population-based data on the relationship between a fitness test and a health outcome or marker in youth. As noted earlier, however, data on the relationship between fitness and health in youth are limited, mainly because of the difficulty of identifying such associations when health constructs in youth are not well defined. When data in youth populations are not avail- able, alternative approaches can be followed to derive cut-points (interim cut-points). Box S-2 provides the committee's guidance on methods for selecting criterion-referenced cut-points and interim cut-points for health- related fitness testing in youth. CONCLUSIONS AND RECOMMENDATIONS The committee developed conclusions and recommendations regard- ing fitness measures for youth for each of four components of fitness: body composition, cardiorespiratory endurance, musculoskeletal fitness, and flexibility. For each of these components, the committee identified test items, reviewed the evidence on these items, applied the general criteria for selection listed earlier, considered modifying factors, assessed the feasibil- ity of implementation, and applied the guidance in Box S-2 for selecting cut-points. In general, the studies reviewed provided insufficient data with which to assess the influence of several potential modifiers--age, gender, race/ethnicity, body composition, maturation status, motor skill--on per- formance on tests of cardiorespiratory endurance, musculoskeletal fitness, and flexibility. As noted earlier, the committee's recommendations are specific to the implementation of fitness measures either in a national youth fitness survey or in schools and other educational settings. The recommended tests for a national youth fitness survey represent valid, reliable, feasible, and safe tests for the assessment of health-related fitness in youth for population- level health-monitoring purposes. National survey fitness tests are intended to be implemented by skilled national administrators of such surveys (i.e., those familiar with the procedures for conducting large surveys and the protocols for fitness tests) in school settings. For schools, recommendations are made for fitness tests that are low in cost and equipment requirements such that they are practical for school-based implementation. Regardless of the setting, test administrators and those interpreting and communicating the results should receive appropriate training in conducting and interpret-
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6 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH BOX S-2 Guidance for Developing Cut-Points The committee determined that a criterion-referenced method should be employed in developing cut-points. That is, a test taker's performance should be compared against an absolute criterion that is related to health. The following are options, depending on the available evidence: · W hen a confirmed concurrent relationship exists between health outcome measures and fitness tests in youth, criterion-referenced cut-points can be determined by using a data-mining procedure that establishes the statistical evidence for that relationship. · When a confirmed concurrent relationship exists only in adults but not in youth, either a relative position or a panel-driven method can be used, whereby interim criterion-referenced cut-points in youth are derived from the percentile values (related to health outcomes) extrapolated from the adult population or by a panel of experts using cut-points for adults and other available information (e.g., growth curves and performance characteristics for different ages and genders). · When no confirmed relationship exists in either youth or adults, a comparatively relative position method can be employed, whereby interim criterion-referenced cut-points are derived from the per- centile values (related to health outcomes) extrapolated from a different test. When the percentile from another test is used, the two tests should be as comparable as possible in their nature (e.g., both require movement of the body) and in the dimension they measure (e.g., upper-body strength). ing the tests to minimize measurement and classification errors and prevent adverse events. Finally, the committee offers recommendations for future research that would advance understanding of youth fitness measures and their association with health outcomes. Conclusions About Components of Fitness The committee's conclusions relate to the four components of fitness detailed above: body composition, cardiorespiratory endurance, musculo- skeletal fitness, and flexibility.
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SUMMARY 7 Body Composition Body composition denotes the sum of the basic components that make up body weight, including fat, muscle, and bone content. The committee defined body composition operationally as a component of fitness, a health marker, and a modifier of fitness. Field-based measures of body composi- tion relate to different dimensions. For example, skinfold is an indicator of subcutaneous fat, whereas waist circumference is an indicator of abdominal adiposity, and BMI measures body weight-for-height. These measures also vary in that they have been associated with different health markers; for example, skinfold measures are related to risk factors for cardiovascular disease and metabolic syndrome, waist circumference has been associated with cardiovascular disease, and BMI is related to risk of diabetes and hypertension. When implementing and interpreting measures of body com- position, it is important to note that many factors, such as physical activ- ity, calorie consumption, age, and maturation, influence body composition measures. The committee selected measures of body composition based on their relationship to health markers, their integrity, and their feasibility. The committee concluded that the above three measures of body com- position--skinfold, waist circumference, and BMI--are important to collect in a national youth fitness survey. Each is a proximal estimation of body fat and has increased standard of error over laboratory measures. Moreover, the measurement of body composition is multidimensional; no single mea- sure is considered representative of all body composition tenets for youth of all morphologies. In selecting measures of body composition, some feasibility factors must be considered: the availability of administrators with the highly spe- cialized training required and the accessibility of appropriate space in which to conduct the test. The reliability of skinfold and waist circumference measurements depends on the skill of the test administrator; to avoid the introduction of errors in the measurements, specific and intense training is required. Training is also required to minimize concerns related to pri- vacy in the administration of these measures. Also to ensure privacy, the appropriate space should be available for conducting the tests. Given the challenges associated with avoiding measurement errors, maintaining good reliability, and ensuring privacy in the administration of skinfold and waist circumference measurements, only BMI measurement is recommended for administration in schools. Cardiorespiratory Endurance Cardiorespiratory endurance is the ability to perform large-muscle, whole-body exercise at moderate to high intensity for an extended period
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8 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH of time. There is a well-established association between cardiorespiratory endurance and health outcomes in adults and health markers or risk factors in children--in particular, body weight, body composition, cardiometabolic risk factors, blood pressure, cognitive function, and pulmonary function. Although the fitness tests and protocols used vary substantially, the cardio- respiratory endurance tests associated most frequently and strongly with a positive change in health markers or risk factors are heart rate extrapolation tests (i.e., those that use a treadmill or cycle ergometer and measure car- diorespiratory endurance as maximal oxygen consumption [VO2max]) and the progressive shuttle run. The health markers most frequently assessed are related to body weight or adiposity and cardiometabolic risk factors. The heart rate extrapolation and progressive shuttle run tests have high validity and reliability. In terms of feasibility, the progressive shuttle run is advantageous when time and financial constraints exist with respect to the necessary training and equipment. Treadmill and cycle ergometer tests are valid and reliable alternatives for a national survey in which space limitations are a concern, but extensive training is feasible. The validity and reliability of distance runs are more variable and in general lower than has been reported for the heart rate extrapolation and progressive shuttle run methods; however, these tests are appropriate for a school setting for practical reasons. Musculoskeletal Fitness Musculoskeletal fitness is a multidimensional construct that encom- passes three related components: muscle strength (the ability of skeletal muscle to produce force under controlled conditions), muscle endurance (the ability of skeletal muscle to perform repeated contractions against a load), and muscle power (the peak force of a skeletal muscle multiplied by the velocity of the muscle contraction). Neither any of these components individually nor any single test can describe overall musculoskeletal fitness. Therefore, a number of tests that measure various dimensions of musculo- skeletal fitness often are used in combination. As with other fitness compo- nents, a wide variety of tests, such as the curl-up, the push-up, the handgrip, and jumps, have been used to measure musculoskeletal fitness in the past. The committee concluded that adequate experimental and prospective longitudinal evidence supports the relationship between the multidimen- sional construct of musculoskeletal fitness and health. Empirical evidence also is increasing for the importance of musculoskeletal fitness, especially muscle strength and power, to health outcomes in adults. There is, however, insufficient high-quality evidence to support a strong association between any single musculoskeletal fitness test item and health markers in youth. Based predominantly on evidence indicating a relationship to health out-
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SUMMARY 9 comes in adults, the committee concluded that musculoskeletal fitness should be assessed in a national youth fitness survey. Growing evidence supports use of the handgrip strength test and the standing long jump as health-related musculoskeletal fitness test items in youth. Studies reviewed show a relationship between performance on these tests and bone health and body composition. The handgrip strength test demonstrates moderate to strong validity when assessed against upper- and lower-body criterion muscle strength measures. The standing long jump, although not strictly a measure of muscle strength, demonstrates acceptable validity against lower- and upper-body criterion muscle strength measures and lower-body muscle power measures. The handgrip strength and standing long jump tests demonstrate strong and moderate reliability, respectively. The committee recommends that the handgrip strength and standing long jump tests be included in a national survey. While these tests should not be interpreted in a health context until their relationships with health outcomes have been established more firmly in youth, they can be included for their educational value. Other measures of muscular strength, such as the modified pull-up or push-up as an alternative for measuring upper-body musculoskeletal strength and power or the curl-up for measur- ing core strength and endurance, also can be used in schools. Flexibility Flexibility is the intrinsic property of body tissues, including muscle and connective tissue, that determines the range of motion achievable without injury at a joint or group of joints. Like musculoskeletal fitness, flexibility is specific; a person can have a good range of motion around a shoulder joint, for example, but lack range of motion in the hip. Such specificity precludes any relationship between a given measure of flexibility and any systemic health markers (e.g., back pain, risk of injury, posture problems). Moreover, clinical theory suggests that the complex interaction among multiple mus- culoskeletal components (e.g., flexibility, strength, endurance), rather than one component alone, is most likely to be associated with health markers or outcomes. Further, possible associations with health are complicated by the fact that risk may be higher for those with low or exceptionally high flexibility than for those in the middle ranges. Finally, although evidence suggests a link between flexibility and health among adults (e.g., low-back pain), such evidence is more difficult to establish in youth given that the commonly used health risk outcomes may take years to manifest. The literature review did not reveal a relationship between any flexibil- ity test and health in youth. In addition to the challenges mentioned above, this could be due to the study designs included in this review. Specifically, in contrast to studies on other fitness components, there was a lack of high-
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10 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH quality longitudinal and experimental studies measuring the association between flexibility and health markers in youth. For example, many studies did not include health markers hypothesized to be related to flexibility and typically did not include a control. Future efforts to study the relationship of flexibility to health will require a multivariate approach. Although no relationship to health has been shown, the sit-and-reach test is feasible to implement and has acceptable validity and reliability. Recommendations for National Surveys A substantial body of evidence supports the idea that specific tests measuring cardiorespiratory endurance and body composition are related to health markers in youth. The evidence for an association between mus- culoskeletal fitness and health markers in youth is less extensive. The com- mittee concluded that insufficient evidence has thus far been accumulated to support recommending a health-related measure of flexibility for youth at this time. The committee concluded that a criterion-referenced approach using cut-points associated with health markers is the ideal approach for inter- preting scores. There is, however, insufficient evidence with which to develop age- and gender-specific criterion-referenced cut-points for all measures except for BMI. Until data are collected with which to establish criterion-referenced cut-points, age- and gender-specific interim cut-points corresponding to percentiles for adults on tests related to the same com- ponent or for youth on tests related to a different or the same component should be used. RECOMMENDATION 8-1.3 A national survey of health-related physical fitness in youth should include measures of cardiorespiratory endurance, body composition, and musculoskeletal fitness. The survey should include the following fitness test items: (1) measures of BMI, waist circumference, and skinfold thickness (triceps and subscapular sites) to assess body composition; (2) a progressive shuttle run, such as the 20-meter shuttle run (or a submaximal treadmill or cycle ergom- eter test if there are space limitations) to measure cardiorespiratory endurance; and (3) handgrip strength and standing long jump tests to measure musculoskeletal fitness. RECOMMENDATION 8-2. Standard protocols for the administration of measures of youth fitness in national surveys should be developed 3The committee's recommendations are numbered according to the chapter of the main text in which they appear.
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SUMMARY 11 and implemented. The focus should be on maximizing the measures' reliability, validity, and safety. Trained personnel should be used for test administration and data collection. RECOMMENDATION 8-3. Developers of fitness test batteries should use age- and sex-specific cut-points to determine which individuals are at risk of poor fitness-related health outcomes. Optimum cut-points should be based on criterion values when population-based evidence is available on the relationship between the level of performance on a fitness test and a health outcome or marker. In the absence of cri- terion values, interim population-based percentile values should be applied. These values might be derived from adults on tests for the same component or from youth on tests for a different or the same component. Specifically, the guidance of the committee should be applied as follows: · ody composition: For BMI, the CDC-established cut-points B for underweight, overweight, and obesity evaluations should be used. Interim cut-points for skinfold and waist circumfer- ence measures could be derived from the CDC-established percentiles for BMI. · Cardiorespiratory endurance: For measures of cardiorespira- tory endurance, interim cut-points could be derived from the lowest performers (e.g., 20th percentile) on the cardiorespira- tory endurance distribution curve. · Musculoskeletal fitness: For musculoskeletal fitness tests, interim cut-points could be derived by borrowing the percentile (e.g., 20th percentile) from the cardiorespiratory endurance tests. Recommendations for Schools and Other Educational Settings The preceding recommendations outline the optimum test items for measuring fitness in youth in national surveys. Conducting fitness tests in educational settings can yield further benefits, such as contributing to the body of evidence on the association between health-related fitness compo- nents and learning outcomes, improving individuals' fitness performance, and educating about the importance of physical fitness. The committee considered the strengths and weaknesses of the test items recommended for a national survey with regard to their practicality in schools and other educational settings. School leaders and teachers should apply the following recommenda- tion and select applicable test items in light of the contextual variables that characterize their schools, such as available equipment, space, and test
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12 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH administrators, as well as cost, as schools differ greatly on these variables. Factors related to culture and race/ethnicity, as well as how a test item aligns with the existing curriculum, should also be considered. Finally, per- haps the most important element of fitness testing in schools is the interpre- tation and dissemination of results. This element represents an opportunity to assist participants in preventing disease and understanding fitness, but can have detrimental effects on the individuals involved if not carried out appropriately. As mentioned above, training in the administration of pro- tocols and the interpretation and communication of test results is essential. RECOMMENDATION 9-1. Developers and administrators of fitness test batteries in schools and other educational settings should consider including the following test items: · tanding height (measure of linear growth status) and weight s (measure of body mass) to calculate BMI as an indicator of body composition; · a progressive shuttle run, such as the 20-meter shuttle run, to measure cardiorespiratory endurance; and · handgrip strength and standing long jump tests to measure upper- and lower-body musculoskeletal strength and power, respectively. Additional tests that have not yet been shown to be related to health but that are valid, reliable, and feasible may also be considered as supple- mental educational tools. For cardiorespiratory endurance, alternatives to the shuttle run include distance and/or timed runs, such as the 9-minute or 1-mile run, while the modified pull-up and push-up are possible alterna- tives for measuring upper-body musculoskeletal strength. The curl-up may be considered in addition to the suggested musculoskeletal fitness tests for measuring core strength and endurance. Although the committee does not recommend a flexibility measure as a core component of a fitness test battery, administrators in schools and other educational settings may wish to include the sit-and-reach test or its alternatives (e.g., backsaver sit-and- reach) to measure flexibility. Experts who establish cut-points for inter- preting performance on these fitness test items should follow the guidance provided earlier (Box S-2 and Recommendation 8-3). Recommendations for Future Research Altogether, the CDC's literature review revealed many gaps in under- standing of the relationship between fitness measures and health in youth. Although the review revealed a number of associations between the two,
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SUMMARY 13 many of the studies reviewed were not designed to assess the independent association between performance on a fitness test and a health outcome or marker. Moreover, while not included in the search strategy, studies predict- ing health outcomes in adulthood would be valuable in characterizing the importance of a health marker. For example, it remains to be determined whether changes in muscle strength and power during youth are predictive of health outcomes in later life. The committee offers the following recommendations for designing and conducting research on some of the most pressing questions that must be answered if progress is to continue in selecting the best measures of fitness in youth. It should be noted that the committee is recommending research only for those test items that have been studied well enough to justify their inclusion here. At the same time, it is not the intent of the committee to eliminate from future consideration those test items that currently do not meet the level of evidence necessary for inclusion in a battery of tests. RECOMMENDATION 10-1. Well-designed research studies aimed at advancing understanding of the associations between fitness compo- nents and health in youth should be undertaken. Researchers should ensure that the interventions studied are both specific and sufficient (i.e., appropriate dosage and duration) to induce a change in fitness. In addition, studies should be designed so that the effect of potential confounders (e.g., nutrition, physical activity, demographic variables, maturity status) and the potential for adverse events can be analyzed. RECOMMENDATION 10-2. Longitudinal studies should be con- ducted to provide empirical evidence concerning how health markers related to fitness track from youth into adulthood. RECOMMENDATION 10-3. Randomized controlled trials and longi- tudinal studies should be undertaken to understand the following issues regarding the relationships between (1) specific fitness tests and health, and (2) fitness components and health: · tudies should explore the relationship between body composi- S tion measures and physical fitness tests and the potential interac- tions among body composition, fitness, and health in youth. · Studies should examine the relationship between changes in cardiorespiratory endurance as measured by field tests, includ- ing the shuttle run and timed and distance runs, and subse- quent changes in health risk factors in youth beyond weight status and cardiometabolic risk factors. Examples include bone health and neurocognitive function and behavior.
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14 FITNESS MEASURES AND HEALTH OUTCOMES IN YOUTH · tudies should address the relationship between specific mus- S culoskeletal fitness test items and health markers in youth. Priority should be given to test items for which there is growing evidence, such as the handgrip strength or standing long jump test, or others that are promising. Since musculoskeletal fitness is a multivariate construct, the studies should be designed so that a variety of tests are conducted. · Studies should investigate the relationship between specific flexibility test items (e.g., sit-and-reach and its modifications), either by themselves or in combination with musculoskeletal fitness test items, and potential health markers (e.g., back pain, posture, injury prevention). Such studies should include stretch- ing interventions specifically designed to produce changes in joint-specific flexibility. Since flexibility is a multivariate con- struct, the studies should be designed so that a variety of tests are conducted. Researchers should investigate the develop- ment and validation of a general marker of musculoskeletal systemic flexibility and its relationship to health markers and risk factors. · Studies should examine the potential effects of modifying fac- tors (i.e., age, gender, race/ethnicity, body composition, matu- rity status, training status/practice, motor skill, socioeconomic factors) on fitness components and on the relationship between a change in a health-related fitness component and health markers in specific populations. RECOMMENDATION 10-4. Developers of national surveys of health-related physical fitness in youth should consider the inclusion of measures of cardiometabolic health, bone health, and neurocogni- tive function. The collection of fitness and health data in the same individuals would allow investigators to further confirm whether direct relationships between specific test items and health markers and risk factors exist. RECOMMENDATION 10-5. When an association between a fitness test and a health marker is confirmed, research should be conducted to establish and validate health-related cut-points for that test. For exam- ple, given the association of skinfold measures with health markers, large national studies should be conducted to establish health-related cut-points for skinfold measures in youth.