al., 2008) and strong reliability (r = 0.71-0.90) in children and adolescents (Benefice et al., 1999; Brunet et al., 2007; Ruiz et al., 2006). It also has minimal test-retest learning and fatigue effects (Ortega et al., 2008a). Given differences in hand sizes among youth, optimal grip span adjustment, elbow angle, and device calibration are important for valid testing.

The standing long jump has been used extensively as a test of lower-body muscular strength, power, and explosive strength (see Table 2-6 in Chapter 2). Although not strictly a measure of power as that subdomain is defined, the standing long jump is the most widely used field-based test of muscle power/explosive strength. It demonstrates moderate to strong correlations with 1RM leg press/body weight (r = 0.39) (Milliken et al., 2008), isokinetic quadriceps torque (r = 0.50) (Holm et al., 2008), and total-body isometric strength (r = 0.77) (Castro-Piñero et al., 2010) in youth. In addition, the standing long jump correlates strongly (r = 0.70-0.91) with other lower- and upper-extremity field-based power tests (i.e., vertical jump, countermovement vertical jump, upper-body explosive throw) in youth (ages 6-17), controlling for age, gender, and BMI and/or weight (Castro-Piñero et al., 2010; Milliken et al., 2008). The standing long jump also has been found to have acceptable reliability in youth (r = 0.52-0.99) (Benefice et al., 1999; España-Romero et al., 2010; Malina et al., 2004; Pena Reyes et al., 2003; Safrit, 1995; Simons et al., 1990). In addition, the reliability of this test appears not to be affected by either systematic bias or sex differences among adolescents (Ortega et al., 2008a), although reliability estimates generally increase with age. Differences in gross motor coordination and experience with jumping across developmental time may influence the degree of test-retest reliability for the standing long jump. Controlling individually for anthropometric variables (i.e., height and body mass) provides a more valid assessment of lower-body strength and power for this test across ages (Castro-Piñero et al., 2010; Milliken et al., 2008).

The modified pull-up and isometric knee extension tests also are valid and reliable tests of upper- and lower-body musculoskeletal fitness, respectively; however, insufficient scientific evidence supports the link between these two tests and health outcomes in youth. The modified pull-up has demonstrated moderate to strong construct validity (r = 0.60-0.79) with other upper-body criterion strength measures (i.e., 1RM bench press, pull-down, arm curl) in boys and girls when measured per unit body weight (Pate et al., 1993). The highest correlation demonstrated (r = 0.75) comprises the sum of the multiple upper-extremity strength tests, which demonstrates strong construct validity for a composite measure of upper-body strength. The modified pull-up also is moderately to strongly correlated (r = 0.64-0.79) with push-ups, thus demonstrating a crossover effect with muscle strength and endurance. Moderate to high test-retest reliability (r = 0.52-0.99) (Engelman and Morrow, 1991; Erbaugh, 1990; Kollath et al.,



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