Reference Standards for Vertical Jump Power and Handgrip Strength for Screening the Risk of Low Bone and Muscle Mass for Age in Youth.

Abstract: Baptista, F, de Marco, RL, Zymbal, V, and Janz, KF. Reference standards for vertical jump power and handgrip strength for screening the risk of low bone and muscle mass for age in youth. J Strength Cond Res XX(X): 000-000, 2025-This study examined the predictive validity of vertical jump power and handgrip strength to discriminate at-risk youth for low muscle mass and bone mass for age. The sample consisted of 529 subjects of ages 10-18 years. Handgrip strength and vertical jump power were assessed using a hand dynamometer and a countermovement jump performed on a force platform. Dual-energy X-ray absorptiometry was used to assess lean body mass normalized for body height (kg·m-2) and bone mineral density (g·cm-2) of the whole body less head. These variables were used to determine the risk of low bone and muscle mass, defined by a Z-score ≤ -1.0 for both variables. All variables were standardized by the lambda-mu-sigma method according to sex and age group, using the sample as a reference. By sex, the analysis included the area under the curve (AUC), sensitivity (Se), and specificity (Sp). The ability to discriminate the risk of low bone and muscle mass through the assessment of musculoskeletal fitness was good to exceptional for vertical jump power (AUCs ≥0.88, Se and Sp = 78-91%) and acceptable to good for handgrip strength (AUCs = 0.75-0.88, Se and Sp = 68-73%). Risk Z-scores for musculoskeletal fitness ranged from -0.5 to -0.8, depending on the test and sex. Handgrip strength and especially vertical jump power can be used to screen the risk of pediatric low bone and muscle mass. Slight decreases in musculoskeletal fitness can be an inexpensive and noninvasive indicator of muscle and bone health.