tion, and posture, and appropriate studies are needed to explore such associations. The limitations described above led the committee not to recommend a flexibility test for a national youth fitness survey. Instead, the committee recommends conducting further research on this fitness component, as well as considering the use of flexibility tests in schools and other educational settings for educational purposes.

Until the relationship to health is confirmed and national normative data and health data are collected for youth, the comparatively relative position method should be used for setting cut-points (cutoff scores) for performance on flexibility tests. With this method, percentiles established for other fitness measures are used to establish interim cut-points for the measure of interest. For example, interim cut-points corresponding to the 20th percentile should be used for flexibility tests, analogous to the cut-points for cardiorespiratory endurance tests.

Flexibility as a component of fitness first gained prominence in the early 1900s as the field of physical therapy emerged (Linker, 2011). Later in that century, circumstances (i.e., two world wars and a polio epidemic) provided further impetus for growth in the professions of occupational and physical therapy and a rise in schools for preparing therapists. In 1980 the first health-related physical fitness test was published (AAHPERD, 1980), and it included a test of flexibility (sit-and-reach). Subsequent U.S. and international health-related test batteries—including the President’s Council on Fitness, Sports and Nutrition (PCFSN) and Fitnessgram® batteries—have included items to measure flexibility.

This chapter reviews existing data on the relationship between flexibility and health outcomes in youth. The focus is on the extent to which flexibility is associated with better health and function, excluding those outcomes related to athletic performance. The chapter begins by defining flexibility and describing the relevant physiology as a basis for explaining the challenges involved in identifying an association between a single flexibility test and a health outcome. The most frequently used flexibility tests are then described. Next, the chapter presents findings from the literature on what is known about the relationship between flexibility and health in adults and in youth, which serve as the basis for the committee’s guidance for interpreting results of flexibility tests, as well as for its conclusions about the associations between flexibility tests and health outcomes in youth. The validity and reliability of these tests are also examined. The process for selecting the studies included here is described briefly in this chapter and in more detail in Chapter 3. Based on its conclusions about the

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