In summary, there is an insufficient body of high-quality literature to support a strong link between performance on any specific musculoskeletal fitness test by youth of either gender and across all ages and stages of development and any health outcomes or markers. The current literature in this area is too fragmented to permit identification of any specific musculoskeletal fitness test item that is unequivocally linked to health in the general population of healthy youth.

VALIDITY AND RELIABILITY OF SELECTED TEST ITEMS

Despite the limitations of the literature discussed above, the growing evidence in youth and stronger evidence in adults is suggestive of a fundamental relationship between musculoskeletal fitness and health outcomes across the life span. The committee finds that handgrip strength test and the standing long jump are two tests that globally represent musculoskeletal strength and power in youth and demonstrate adequate validity, reliability, and feasibility of administration for inclusion in fitness test batteries for all youth. This section reviews the validity and reliability of these two tests, for which there is some, albeit limited, evidence for a relationship to health in the literature reviewed. It also looks at the integrity of the modified pull-up and isometric leg extension tests, which also may be useful for assessing musculoskeletal fitness; however, the literature review provided very limited high-quality evidence for a link to health outcomes in youth for these two tests.

While numerous fitness tests purportedly measure muscle strength, endurance, and power in youth, information about their validity and reliability is limited. Nevertheless, an increasing body of literature pertaining to the validity and reliability of a few musculoskeletal fitness tests provides reasonable justification for including these tests in a test battery for assessment of musculoskeletal fitness in youth. As mentioned above, the committee’s systematic literature review included muscle strength and endurance, but not muscle power, as components of fitness. Some of the tests reported, however, such as throwing and jumping tests, purportedly assess some aspects of muscle power (e.g., average, peak, instantaneous, and contractile power). Although the specific associations between individual fitness tests and aspects of muscle power are poorly defined, the committee’s discussion of the validity of the tests takes account of the fact that the selected tests of musculoskeletal fitness could measure either muscle strength, endurance, or power.

The handgrip strength test is used extensively in European youth fitness testing. Based on the available literature, the handgrip strength test has moderate to strong construct validity (r = 0.52-0.84) with established upper-body (i.e., 1RM bench press) and lower-body (i.e., leg press and isokinetic knee extensor torque) strength tests (Holm et al., 2008; Milliken et



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