mon measures of anaerobic power, the Wingate Anaerobic Test. Because of its unique physiological and neuromechanical characteristics, muscle power is considered one of three dimensions of musculoskeletal fitness in youth fitness assessments.
A plethora of fitness test batteries and items have been used over the past 55 years to assess musculoskeletal fitness in youth (see Table 2-6 in Chapter 2) (Castro-Piñero et al., 2010). The tests vary in their specific protocols, some purportedly assessing the muscle fitness of specific body regions (upper and lower body, trunk, abdomen, lower back) and some measuring isolated muscular function (e.g., muscle strength, endurance, or power) or combined strength and endurance function.
Since the mid-1970s, there has been growing interest in and development of health-related musculoskeletal fitness test batteries that have been based largely on theoretical construct validity and on health data from the adult population (AAHPERD, 1984; Jackson, 2006; Morrow et al., 2009; Plowman, 2008). The American Alliance for Health, Physical Education, Recreation and Dance (AAHPERD) Health Related Physical Fitness Test, the first of many subsequent international fitness test batteries to claim assessment of health-related fitness in youth, included the modified, timed (1-minute) sit-up as the sole measure of musculoskeletal fitness.
More than 11 different classes of fitness test items have since been used to assess the muscle strength, endurance, or power dimensions of musculoskeletal fitness, many of them evaluating similar dimensions (Table 6-1). For example, there are several variations on the pull-up test of differing durations (no time limit, 30- or 60-second limit), with different anatomical alignment of the body (full arm extension or right-angled pull-up), and with varying interpretations of what the test items actually measure (upper-body strength, upper-body endurance, combined upper-body strength and endurance, athletic ability, relative strength).
It is apparent that many of these test items do not satisfy the physiological definitions of the three dimensions of musculoskeletal fitness. Muscle endurance fitness test items arguably may be considered the most physiologically valid field tests in youth as opposed to those measuring muscle strength and power, which are more subject to velocity control, loads, and number of repetitions. Additionally, several of the currently used field-based fitness tests (e.g., curl-up and pull-up) purport to measure more than one musculoskeletal dimension concurrently. Because of their lower construct validity, results of muscle strength and power tests must be interpreted cautiously in youth.