Refining the FitnessGram with criterion-referenced Standards for Musculoskeletal Fitness

In the four decades since the Cooper Institute first developed FitnessGram, research, evaluation, validation, and program enhancement by the Scientific Advisory Board (SAB, https://fitnessgram.net/advisory-board/) have made FitnessGram “the most trusted and widely used fitness assessment, education, and reporting tool in the world” (Plowman et al., 2006; The Cooper Institute, 2022). The sustained commitment by the SAB to science-informed practice including use of criterionreferenced standards based on health outcomes (instead of performance indicators or normative data) has led to refinements in fitness assessments and standards including those for aerobic capacity and body composition (Welk et al., 2011). With the release of the Institute of Medicine’s (IOM) seminal report “Fitness Measures and Health Outcomes in Youth” in 2012, the SAB and The Cooper Institute acknowledged the need to review the FitnessGram musculoskeletal fitness assessments. Specifically, the SAB developed a comprehensive plan to establish and evaluate health-related fitness standards for musculoskeletal fitness. The FitnessGram battery historically included field-based assessments of muscle strength and endurance (i.e., curl-up, push-up, and trunk lift) and flexibility (i.e., back-save sit and reach), but evidence was lacking to support the utility of criterion-referenced health standards for these outcomes. Thus, in this special issue of MPEES, SAB researchers, and colleagues present their findings from a foundational series of studies that aim to fill knowledge gaps related to musculoskeletal fitness assessments in youth. In the first paper, Welk et al. (2022) review and summarize the concepts, approaches, and considerations used by the SAB to explore the development of criterion-referenced standards for musculoskeletal fitness in youth. The authors first outline their conceptual model of health-related fitness and musculoskeletal fitness, with the latter defined as per the IOM as a multidimensional construct encompassing the integrated function of muscle strength, muscle endurance, and muscle power (Institute of Medicine, 2012). The SAB’s model for musculoskeletal fitness guided selection of fitness tests to represent the upper (i.e., grip strength) and lower body (i.e., vertical and long jump) and core (i.e., plank test), with the acknowledgment that one single measure cannot capture this complex construct. As mentioned, criterion-referenced health standards are a foundational and unique element of FitnessGram (Cureton & Warren, 1990; Plowman et al., 2006; Zhu et al., 2011), and the SAB adhered to their established methods when developing standards for musculoskeletal fitness. The process first involves modeling age and sex effects using the Lambda Mu Sigma (LMS) procedures (described in detail elsewhere (Cole, 1990; Cole & Green, 1992)), which are used in three papers in this special issue (Laurson et al., 2022a, 2022b, 2021). Development of LMS curves is followed by receiver operator characteristic (ROC) analyses to identify thresholds for predicting an associated health outcome. Similar to the pioneering approach, the SAB utilized when refining the aerobic fitness and body composition standards, two distinct thresholds were defined with the ROC analyses which permitted categorization of fitness scores into three zones – a healthy zone, a risk zone, and a marginal or intermediary zone. Welk and colleagues outlined other unique considerations of the SAB when setting the musculoskeletal fitness standards including prioritizing indicators directly related to the musculoskeletal system (i.e., bone and muscle health), basing standards on absolute indicators of strength and endurance instead of on measures relative to body weight, and developing standardized protocols for the three primary