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This study aimed to evaluate developmental patterns in athletic performance during youth and determine their association with changes in physical fitness. The testing included three athletic performance (i.e. ball speed in pitching, swing velocity in batting, 30-metre sprint time) and two physical fitness tests (i.e. medicine ball [MB] back throw and modified star excursion balance test [SEBT]). Data from 235 players (557 measurements) aged 6 to 14 were eligible for a longitudinal evaluation. The statistical analysis was based on the latent growth curve models of the athletic performance development process and the random-effect panel data multivariate regression analysis for ball speed, swing velocity, and 30-metre sprint time. The 30-metre sprint time showed a small curvature but an accelerated increase around 12‒13 years old. However, the ball speed, swing velocity, and modified SEBT demonstrated a slower or less accelerated change in the developmental pattern starting around 12‒13 years old. Multivariate longitudinal analysis revealed that developmental change in athletic performance was positively associated with age and MB back throw. Our findings highlight the developmental patterns of athletic performance associated with baseball exhibiting stagnation as well as acceleration, which may help develop effective age-appropriate strategies for improving performance in youth baseball players. [ABSTRACT FROM AUTHOR]

Background: Calcaneal apophysitis is the most common cause of heel pain in children and adolescents. However, the relationship between skeletal maturity and heel pain in the specific youth cohort is unclear., Purpose: To clarify the relationship between the maturity stages of the calcaneal apophysis and heel pain in youth baseball players., Study Design: Cross-sectional study; Level of evidence, 3., Methods: A total of 336 youth male baseball players participated in this study. Ultrasound scanning of the calcaneal apophysis was performed along the longitudinal line connecting the middle of the Achilles tendon, the middle of the calcaneus, and the second toe, between the proximal calcaneal edge and the medial calcaneal tubercle. The authors classified the maturity of the calcaneal apophysis into 5 stages, from nonpresence of the apophysis (stage 1) to complete fusion (stage 5). The diagnosis of heel pain was based on subjective report of feeling pain on the squeeze test. The relationship between the maturity stages and physical characteristics was investigated using 1-way analysis of variance or the Kruskal-Wallis test, and the relationship between the maturity stages and heel pain was investigated using the chi-square test., Results: Of the 336 players, 49 had heel pain, for a prevalence of 14.6%. Eighteen (5.4%) players had unilateral heel pain, and 31 (9.2%) players had bilateral heel pain. There were no significant differences in the maturity stages of the calcaneal apophysis between the players with no heel pain and those with heel pain. However, no players had heel pain during stage 5, when the calcaneus had completed its maturation., Conclusion: The prevalence of heel pain was 14.6% in Japanese youth male baseball players. There was no relationship between the maturity stages of the calcaneal apophysis and heel pain. Heel pain that could be associated with calcaneal apophysitis did not occur during stage 5, when maturation of the calcaneal apophysis was complete., Competing Interests: The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2024.)

Background: Growth-specific physical characteristics in adolescence may mediate throwing-related loads and movement patterns associated with elbow injuries. In a previous study, the authors calculated the forearm-hand inertia, which is the moment of inertia centered at the elbow joint., Purpose: To determine the relationship of forearm-hand inertia values with throwing motion patterns and elbow valgus load in adolescent baseball players., Study Design: Descriptive laboratory study., Methods: A total of 35 adolescent baseball players underwent measurements by dual-energy x-ray absorptiometry (DXA) scans and a throwing trial. Forearm-hand inertia was determined as the joint moment around the elbow using the subregion analysis mode of DXA. Elbow valgus torque and ball speed during throwing were measured using a dedicated sensor and speed gun, and throwing efficiency was calculated by dividing the elbow valgus load by the ball speed. Players were divided according to the throwing motion pattern in which maximum acceleration occurred: pelvis-upper arm-forearm (proximal-to-distal sequencing [PDS] group; n = 19) or pelvis-forearm-upper arm (proximal upper extremity [PUE] group; n = 16). The groups were compared in terms of ball speed, elbow valgus torque, throwing efficiency, and forearm-hand inertia using t tests and analysis of covariance, with forearm-hand inertia as covariates. The chi-square test was used to examine the relationship between throwing motion patterns and forearm-hand inertia., Results: The PUE group had a higher elbow valgus load (effect size [ES] = 0.65; P = .03), throwing efficiency (ES = 0.63; P = .02), and forearm-hand inertia values (ES = 0.64; P = .04) than the PDS group. In addition, a significant relationship was observed with throwing patterns when forearm-hand inertia values were 350 kg·m 2 (OR, 2.36; 95% CI, 1.09-5.12; P = .012) and 400 kg·m 2 (OR, 1.68; 95% CI, 0.99-2.85; P = .037)., Conclusion: Study results indicated that growth-specific physical characteristics in adolescent baseball players exhibited in forearm-hand inertia mediated the relationship between high elbow valgus and poor throwing efficiency caused by poor throwing motion patterns., Clinical Relevance: A better understanding of the details in muscle function with throwing mechanics may prevent future injuries., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: This study was funded in part by a grant from the Japan Sports Medicine Foundation (2021). AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2024.)