Comparison of passive torque during shoulder internal rotation before and after a pitching in college baseball pitchers / 体力科学

Previous study reported that baseball pitchers had a decreased shoulder internal rotation (IR) range of motion after pitching. However, whether the decreased range of motion associated with pitching is caused by tightness of the posterior shoulder has not been clarified yet. The joint stiffness in the passive torque can be compared with posterior shoulder tightness before and after pitching. Hence, this study aimed to compare shoulder IR stiffness based on passive torque before and after pitching in baseball pitcher. Eleven health male collage baseball pitchers were recruited. Passive torque during IR (max IR, peak torque and stiffness) of dominant and non-dominant arms was measured using an isokinetic dynamometer. Measurements were taken before, after, and post 24 hours after pitching (105 pitches). It was observed that after pitching, max IR and peak torque were significantly decreased compared to those before pitching. However, there was no difference in the stiffness of passive torque among three measurements. In conclusion, healthy college baseball pitchers have a decreased IR range of motion after pitching. However, this result is not due to posterior shoulder tissue tightness, but because of altered stretch tolerance.

Fundamentos físicos del gesto técnico del pitcher / Fundamentos físicos do gesto técnico do lançador / Physical foundations of the pitcher's technical gesture

RESUMEN La codicia por lanzar duro en el béisbol, más el desconocimiento mecánico-energético del aporte y lo que evita la correcta ejecución de las fases del gesto técnico del pitcher, resultaron ser las principales causas de las lesiones y el motivo de una investigación explicativa, a través de la aplicación de métodos físicos cinemáticos, dinámicos y energéticos, en el estudio de la manifestación de leyes físicas durante la observación no participativa de su desempeño, al lanzar la pelota, tanto en lanzadores nacionales como internacionales y de testimonios de personas con experiencias como pitcher. El objetivo de este artículo consistió en proponer una explicación física de cómo funciona la biomecánica del cuerpo del pitcher durante los gestos técnicos del lanzamiento para garantizar una bola rápida y minimizar lesiones. Con este trabajo, se pretendió, además, instruir al pitcher de cómo funciona la biomecánica de su cuerpo durante el lanzamiento de la pelota, aprovechando ventaja de la altura del montículo con argumentos desde la ciencia Física; esto contribuyó a lanzamientos más rápidos, elegantes y a minimizar lesiones. Como resultado, se elaboró una explicación física por fases para el pitcher, además, un sistema masa-resorte aislado para experimentar movimientos biomecánicos y energéticos, que evidenciaron en su desempeño manifestaciones de las leyes físicas de la mecánica clásica de Newton, de la conservación de la energía mecánica, del momento cinético y del momento angular.

RESUMO A ganância de jogar duro no basebol, mais a ignorância mecânico-energética da contribuição e o que impede a correta execução das fases do gesto técnico do lançador, revelaram-se as principais causas de lesões e a razão de uma pesquisa explicativa, através da aplicação de métodos físicos cinemáticos, dinâmicos e energéticos, no estudo da manifestação das leis físicas durante a observação não participativa do seu desempenho, ao lançar a bola, tanto em lançadores nacionais como internacionais e testemunhos de pessoas com experiências como lançadores. O objetivo deste artigo é propor uma explicação física de como funciona a biomecânica do corpo do lançador durante os gestos técnicos de lançamento para garantir uma bola rápida e minimizar as lesões. Com este trabalho, pretende-se também instruir o lançador sobre como funciona a biomecânica do seu corpo durante o lançamento da bola, tirando partido da altura do monte com argumentos da ciência física. Isto contribui para campos mais rápidos e mais elegantes e para minimizar as lesões. Como resultado, foi elaborada uma explicação física por fases para o jarro, além disso, um sistema isolado de suspensão em massa para experimentar movimentos biomecânicos e energéticos, que evidenciou no seu desempenho, manifestações das leis físicas da mecânica clássica de Newton, da conservação da energia mecânica, do momento cinético e do momento angular.

ABSTRACT The greed to throw hard in baseball, plus the mechanical-energetic ignorance of the contribution and what prevents the correct execution of the phases of the pitcher's technical gesture, turned out to be the main causes of injuries and the reason for an explanatory research, through the application of physical kinematic, dynamic and energetic methods, in the study of the manifestation of physical laws during the non-participatory observation of their performance, when throwing the ball, both in national and international pitchers and testimonies of people with experiences as pitchers. The objective of this article is to propose a physical explanation of how the biomechanics of the pitcher's body works during the technical gestures of pitching to guarantee a fast ball and minimize injuries. With this work, it is also intended to instruct the pitcher on how the biomechanics of his body works during the pitching of the ball, taking advantage of the height of the mound with arguments from the physical science. This contributes to faster, more elegant pitches and to minimize injuries. As a result, a physical explanation by phases was elaborated for the pitcher, in addition, an isolated mass-spring system to experiment biomechanical and energetic movements, which evidenced in their performance manifestations of the physical laws of Newton's classical mechanics, conservation of mechanical energy, kinetic momentum and angular momentum.

Indicadores de rendimiento deportivo para el proceso de selección del lanzador abridor / Indicadores de desempenho esportivo para o processo de seleção de batedores iniciais / Sports performance indicators for the opening pitcher selection process

RESUMEN El talento deportivo no se define por una sola capacidad, sino por la interrelación y complementación, lo que implica análisis y valoraciones integrales. En el béisbol, a pesar de que cuenta con programas de preparación del deportista, actualizados y de parámetros establecidos para la selección deportiva, aún continúan siendo deficientes los indicadores que permiten una selección objetiva para cumplir funciones especializadas, lo que constituye un aspecto de esencial importancia en el desempeño competitivo contemporáneo. Sin embargo, en el proceso de conformación de los equipos a participar en campeonatos nacionales, se evidencian insuficiencias que limitan la calidad de su alcance. De ahí que el objetivo general de la investigación consistió en proponer indicadores de rendimiento deportivo para el proceso de selección del lanzador abridor, en la conformación de equipos de béisbol de alto rendimiento en la Isla de la Juventud. Se seleccionó una muestra compuesta por 11 lanzadores de béisbol de la categoría juvenil de la Isla de la Juventud que representa el 52,38 % de la población; de ellos, ocho son derechos que representan el 72.72 % y tres zurdos que representan el 27.27 %, además de cuatro entrenadores que representan el 19,04 % y 6 especialistas que representan 28,57 % de la población. Los métodos de investigación empleados fueron la observación, revisión de documentos normativos que rigen el proceso de selección deportiva en el béisbol, la encuesta a entrenadores y el criterio de especialistas, lo que permitió identificar la inexistencia de una herramienta que oriente la labor del profesor deportivo en lo referido a la selección de los lanzadores abridores.

RESUMO O talento esportivo não é definido por uma única capacidade, senão pela inter-relação e complementação, que envolve análise e avaliações abrangentes. No beisebol, apesar de ter atualizado programas de preparação dos atletas e estabelecido parâmetros para a seleção esportiva, os indicadores que permitem uma seleção objetiva para cumprir funções especializadas ainda são deficientes, o que é um aspecto de importância essencial no desempenho competitivo contemporâneo. Entretanto, no processo de conformação das equipes para participar de campeonatos nacionais, existem insuficiências que limitam a qualidade de seu escopo. Assim, o objetivo geral da pesquisa foi propor indicadores de desempenho esportivo para o processo de seleção do arremessador titular, na conformação de equipes de beisebol de alto rendimento na Ilha da Juventude. Foi selecionada uma amostra composta por 11 jogadores de beisebol da categoria jovem da Ilha da Juventude, representando 52,38 % da população; oito deles são destros, representando 72,72 % e três são canhotos, representando 27,27 %, além de quatro treinadores representando 19,04 % e 6 especialistas representando 28,57 % da população. Os métodos de pesquisa utilizados foram a observação, a revisão de documentos normativos que regem o processo de seleção esportiva no beisebol, o levantamento dos treinadores e os critérios dos especialistas, o que permitiu identificar a inexistência de uma ferramenta para orientar o trabalho do professor de esportes em relação à seleção dos arremessadores iniciantes.

ABSTRACT Sports talent is not defined by a single capacity, but by the interrelation and complementation, which implies comprehensive analysis and assessments. In baseball, in spite of having updated athlete preparation programs and established parameters for sports selection, the indicators that allow an objective selection to fulfill specialized functions are still deficient, which is an aspect of essential importance in contemporary competitive performance. However, in the process of forming the teams to participate in national championships, there are insufficiencies that limit the quality of their scope. Hence, the general objective of the research consisted in proposing sports performance indicators for the selection process of the opening pitcher, in the conformation of high performance baseball teams in La Isla de la Juventud. A sample composed of 11 baseball pitchers of the youth category of La Isla de la Juventud was selected, representing 52.38 % of the population; of them, eight are right-handed representing 72.72 % and three are left-handed representing 27.27 %, in addition to four coaches representing 19.04 % and 6 specialists representing 28.57 % of the population. The research methods used were observation, review of regulatory documents governing the process of sports selection in baseball, the survey of coaches and the criteria of specialists, which allowed identifying the lack of a tool to guide the work of the sports teacher in relation to the selection of the opening pitchers.

Efectividad en la zona de strike de los lanzadores pinareños / Eficácia na zona de strike dos lançadores de Pinar del Rio / Effectiveness in the strike zone of the pitchers from Pinar del Río

Resumen Teniendo presente la importancia del pitcheo y su peso para el éxito en el juego de béisbol, es que el objetivo de la investigación se centra en analizar la efectividad en la zona de strike de los lanzadores del equipo de béisbol de Pinar del Río, primera categoría, participantes en la Serie Nacional. Par ello, se trabajó con una población integrada por los 13 lanzadores que constituyen el staff de pitcheo y los dos entrenadores responsables de la preparación de estos en dicho equipo. Se emplearon métodos y técnicas científicas como el análisis de la estadística de cada uno de los juegos, así como la observación, la encuesta y la entrevista. El análisis de los resultados obtenidos revela que el 61,5 % de los lanzadores del equipo, fundamentalmente los más jóvenes, presentan problemas con el control de los lanzamientos en la zona de strike, aflorando una serie de insuficiencias relacionadas con el dominio de la mecánica de pitcheo, el escaso repertorio de lanzamientos, unido a un bajo dominio sobre los mismos, entre otros elementos vinculados a la preparación. Estos resultados, junto al control sistemático y análisis de la labor de los lanzadores durante los juegos, constituyen elementos importantes para trazar estrategias más eficientes en la preparación de estos atletas, atemperadas a sus particularidades individuales e insuficiencias, en aras de lograr una mayor efectividad de los mismos, y, por ende, superar los resultados competitivos del equipo.

Resumo Tendo em conta a importância do lançamento e o seu peso para o sucesso no jogo de basebol, o objectivo do presente trabalho está centrado na análise da efetividade na zona de strike dos lançadores da equipe de basebol de Pinar del Río, primeira categoria, participantes da Série Nacional. Para isso, trabalhamos com uma população composta pelos 13 lançadores que integram a equipe de pitcheo e os dois técnicos responsáveis pela preparação destes em tal equipe, para o qual foram utilizados métodos e técnicas científicas, como a análise das estatísticas de cada um dos jogos, assim como a observação, o inquérito e a entrevista. A análise dos resultados obtidos revela que 61,5% dos lançadores da equipe, principalmente os mais jovens, apresentam problemas com o controle dos lances na zona de strike, revelando uma série de deficiências relacionadas com o domínio da mecânica de lançamento, o escasso repertório de lançamentos, juntamente com um domínio baixo sobre os mesmos, entre outros elementos ligados à preparação. Estes resultados, juntamente com o controle e análise sistemática do trabalho dos lançadores durante os jogos, constituem elementos importantes para traçar estratégias mais eficientes na preparação destes atletas, temperados às suas particularidades e insuficiências individuais, a fim de alcançar uma maior efetividade dos mesmos e, portanto, para superar os resultados competitivos da equipe.

Abstract Bearing in mind the importance of pitching and its weight for the success in the baseball game, the objective of the present work is focused on the analysis of the effectiveness in the strike zone of the pitchers of the Pinar del Río baseball team, first category, participants in the national series. For this purpose, it was worked with a population integrated by the 13 pitchers that constitute the pictching staff and the two coaches responsible for the preparation of these in such team, for which we used scientific methods and techniques such as the analysis of the statistics of each one of the games, as well as observation, survey and interview. The analysis of the results obtained reveals that 61,5 % of the pitchers of the team, mainly the youngest ones, present problems with the control of the throws in the strike zone, revealing a series of deficiencies related to the domain of the mechanics of pick-up, the scarce repertoire of throws, together with a low domain on the same ones, among other elements linked to the preparation. These results, together with the systematic control and analysis of the work of the throwers during the games, constitute important elements to trace more efficient strategies in the preparation of these athletes, tempered to their individual particularities and insufficiencies, in order to achieve a greater effectiveness of the same and therefore to overcome the competitive results of the team.

Metodología para el perfeccionamiento del accionar técnico táctico de los lanzadores de béisbol / Methodology for the improvement of the tactical technical action of baseball pitchers

Resumen El accionar técnico táctico de los lanzadores de béisbol exige la búsqueda de herramientas novedosas que se deriven en un contexto pedagógico que gestione, de manera creativa, las formas del conocimiento; a tono con esto, las metodologías actuantes en béisbol reclaman una continua actualización en el orden teórico, metodológico y práctico. De ahí que la presente investigación tuvo por objetivo elaborar una metodología para el perfeccionamiento del accionar técnico-táctico de los lanzadores de béisbol, en correspondencia con la función que desempeñan dentro del juego. Para ello se trabajó con una muestra primaria de 15 lanzadores del equipo Pinar del Río, en el último año de la categoría 17-18, así como una muestra secundaria de 12 entrenadores, 20 especialistas y 20 atletas que incursionan regular u ocasionalmente como lanzadores. Se emplearon métodos y técnicas científicas de investigación como el análisis de documentos, la observación, la entrevista estandarizada e individual y el criterio de expertos. Se constataron carencias en el tratamiento del contenido de la preparación técnico-táctica para el perfeccionamiento del accionar del lanzador de béisbol, según la función que desempeña en el juego, a partir de la cual se propone una metodología que contiene la estructura, contenido y planificación de la preparación técnica-táctica de los lanzadores de béisbol, según su función en el juego, a partir de situaciones simplificadas que didácticamente actúan sobre los componentes de esta preparación deportiva y bajo leyes y principios del entrenamiento deportivo.

Abstract The technical tactical action of baseball pitchers requires the search for new tools that are derived in a pedagogical context that creatively manages the forms of knowledge, in line with this, the methodologies used in baseball demand a continuous updating in the theoretical, methodological and practical order. Hence, the objective of the present research was to develop a methodology for improving the tactical technical action of baseball pitchers in correspondence with the function they perform within the game. In order to do this, we worked with a primary sample of 15 pitchers from the Pinar del Río team, in the last year of the 17-18 category, as well as a secondary sample of 12 coaches, 20 specialists and 20 athletes who regularly or occasionally enter as pitchers. Scientific research methods and techniques such as document analysis, observation, standardized and individual interviews and expert judgment were used. There were shortcomings in the treatment of the contents of the tactical technical preparation for improving the actions of the baseball pitcher according to the role played in the game, from which a methodology is proposed that contains the structure, content and planning of the technical-tactical preparation of baseball pitchers, according to their function in the game, from simplified situations that didactically act on the components of this sports preparation and under laws and principles of sports training.

Elbow Impingement Syndrome in Athletes / 대한스포츠의학회지

Overhead athletes often suffer from elbow injuries due to repetitive throwing movements. In particular, in the baseball pitching motion, a high shear torque generated in the late corking and early acceleration stage causes tensile loads on the medial elbow and shear force on the posterior of the elbow. These repetitive movements can lead to valgus extension overload syndrome. The valgus extension overload syndrome mainly occurs in overhead athletes, and is characterized by limited elbow flexion and pain at the end of extension. It is necessary to differentiate from the stress fracture or the avulsion fracture of the olecranon which complain of posterior elbow pain through computed tomography. The treatment is primarily rehabilitation that restricts the elbow motion. If refractory or mechanical symptoms persist, arthroscopic surgery may be an effective treatment modality for the removal of the osteophytes. In the surgical field, it is desirable to reconstruct the medial collateral ligament when it is confirmed that the ligament is ruptured. Patients who underwent arthroscopic removal of olecranon osteophytes had immediate active elbow exercises and for 3 months were prohibited from pitching exercises. During this period, they were rehabilitated with the focus on strengthening muscles around the scapula, rotator cuff and shoulder. After 3 months, the pitching exercise is gradually started. Six months after the operation, the elbow strength should be restored to the level at which the game starts. Patients who underwent a combined ulnar collateral ligament reconstruction, half pitching are allowed at 6 months.

Shoulder and Elbow Injury Rates and Patterns in Korean Rookie Professional Baseball Pitchers

BACKGROUND: To investigate how many rookie pitchers suffered from injuries while playing in the amateur league without guidelines for prevention of excessive pitching, we analyzed their amateur pitching patterns based on the pitch count, use of breaking balls, and pitches during winter camp. METHODS: Forty-one rookie pitchers who graduated from high school or university in 2013 and joined professional baseball teams. Participants were interviewed by a trainer using our questionnaire. Injury inclusion criteria were 1) history of shoulder surgery, 2) history of elbow surgery, 3) shoulder pain requiring treatment, and 4) elbow pain requiring treatment. RESULTS: Mean number of pitches per game and warm-up pitches for practice was 84.5 pitches (range, 15 to 130 pitches) and 16.4 pitches (range, 2 to 210 pitches), respectively. Mean number of pitches during the last year was 906.9 (range, 80 to 2,000). Mean number of maximal pitches was 127 pitches (range, 50 to 210 pitches). Fourteen pitchers had pitched over 150 pitches. Twenty-seven pitchers (65.9%) had pitched in spite of enduring pain. During winter training (mean 1.8 months), mean number of pitches per day was 162.5 pitches, and 20 pitchers (48.8%) had practiced pitching excessively despite the cold weather. Twenty-six rookies (63.4%) had shoulder pain or history of shoulder surgery, and 31 pitchers (75.6%) had elbow pain or history of elbow surgery. Only four participants (9.8%) did not have pain and history of surgery. CONCLUSIONS: For young baseball pitchers, guidelines for prevention of excessive pitching and for regulating the winter training program may be needed.

Shoulder and Elbow Injury Rates and Patterns in Korean Rookie Professional Baseball Pitchers

BACKGROUND: To investigate how many rookie pitchers suffered from injuries while playing in the amateur league without guidelines for prevention of excessive pitching, we analyzed their amateur pitching patterns based on the pitch count, use of breaking balls, and pitches during winter camp. METHODS: Forty-one rookie pitchers who graduated from high school or university in 2013 and joined professional baseball teams. Participants were interviewed by a trainer using our questionnaire. Injury inclusion criteria were 1) history of shoulder surgery, 2) history of elbow surgery, 3) shoulder pain requiring treatment, and 4) elbow pain requiring treatment. RESULTS: Mean number of pitches per game and warm-up pitches for practice was 84.5 pitches (range, 15 to 130 pitches) and 16.4 pitches (range, 2 to 210 pitches), respectively. Mean number of pitches during the last year was 906.9 (range, 80 to 2,000). Mean number of maximal pitches was 127 pitches (range, 50 to 210 pitches). Fourteen pitchers had pitched over 150 pitches. Twenty-seven pitchers (65.9%) had pitched in spite of enduring pain. During winter training (mean 1.8 months), mean number of pitches per day was 162.5 pitches, and 20 pitchers (48.8%) had practiced pitching excessively despite the cold weather. Twenty-six rookies (63.4%) had shoulder pain or history of shoulder surgery, and 31 pitchers (75.6%) had elbow pain or history of elbow surgery. Only four participants (9.8%) did not have pain and history of surgery. CONCLUSIONS: For young baseball pitchers, guidelines for prevention of excessive pitching and for regulating the winter training program may be needed.

Scapulothoracic Bursitis in a Amateur Baseball Pitcher / 대한스포츠의학회지

Scapulothoracic bursitis refers to inflammation of the bursae secondary to trauma or overuse owing to sports activities or work. It usually causes persistent pain and scapulothoracic crepitus by irritation of bursa but can be presented as painless mass around chest wall. We report a case of scapulothoracic bursitis in a baseball pitcher presenting as rapidly growing chest wall mass confused with a soft tissue tumor. Computed tomography and magnetic resonance imaging revealed as a well-demarcated cystic mass situated between the scapula and chest wall. Incisional drainage resulted in complete resolution of the mass within a couple of weeks. Scapulothoracic bursitis may be presented as painless huge mass in overhead sports athlete and one of the differential diagnoses of soft tissue tumor of the chest wall.

The relationship between asymmetric characteristics of muscle thickness and ball speed in baseball pitchers / 体力科学

The primary purpose of this study was to investigate whether the baseball pitchers have asymmetric characteristics of muscle thickness (MT) in upper extremities, trunk, and lower extremities because of repetitive pitching. The secondary purpose of this study was to investigate the relationship between MT and ball speed. Twenty-six college baseball pitchers participated in this study. Twenty-six sites were selected to quantify the asymmetric characteristics of MT. The MT was measured by a B-mode ultrasound. The ball speed, measured by a radar gun, was used to quantify the pitching performance. The MT of forearm, subscapula, and chest in dominant side (pitching side) were significantly greater than those in nondominant side, and the MT of abdomen, lateral abdomen, and anterior thigh in nondominant side were significantly greater than those in dominant side. On the other hand, the MT of forearm in both sides and the MT of lateral abdomen in dominant side were significantly and positively correlated with ball speed. These results suggest that asymmetric muscle thickness in upper extremity, trunk, and lower extremity in baseball pitchers resulted from repetitive pitching, and the MT of forearm and lateral abdomen are related to the ball speed.

MUSCLE VOLUME AND STRENGTH CHARATERISTICS OF THE ROTATOR CUFF AND DELTOID MUSCLES IN ASYMPTOMATIC BASEBALL PITCHERS / 体力科学

The purpose of this study was to investigate muscle volume (MV) and strength characteristics of the rotator cuff (supraspinatus, infraspinatus, teres minor, and subscapularis) and deltoid muscles in each shoulder of asymptomatic baseball pitchers. Twelve collegiate baseball pitchers (PG) and ten male students (CG) who never played an overhand sports volunteered to participate in this study. Magnetic resonance imaging (Straits II, Hitachi Medico, 1.5 T) was used to measure the MV of rotator cuff and deltoid muscles in both shoulders of each subject. Since the individual muscles were difficult to identify on MRI scans, the infraspinatus and teres minor were analyzed as one infraspinatus muscle. Shoulder abduction (ABD), external rotation (ER), and internal rotation (IR) strengths were measured each side using a hand-held dynamometer (Power Track II, Jtech Medical Industry) . The MV of deltoid muscle was significantly larger value on the dominant side (DOM) than on the non-dominant side (NDOM) in both the PG and CG groups (p<0.05) . However, no significant differences in the MV of the rotator cuff muscles and the measured shoulder strength (ABD, ER, and IR) were observed between both sides in either group. Similarly, no significant differences in the DOM/NDOM ratio of the muscle volume and the measured shoulder strength were observed between the two groups. These results suggest that the rotator cuff muscle volume and strength does not differ in both sides of the PG, and DOM/NDOM ratios of the rotator cuff muscle volume and strength of the PG does not differ in those of the CG.

Hyperextension Overload Syndrome of the Elbow in Baseball Pichers / 대한정형외과학회잡지

Some baseball pichers have the symptom-complex of the elbow joint due to repetitive throwing. The Hyperextension overload syndrome is symptom-complex caused by impingement between olecranon tip and fossa during hyperextension of the elbow. The patients of hyperextension overload syndrome is have some pathology of his elbow such as bony spur on olecranon tip, intra-articular loose body or degenerative arthritis. And they complaint of pain or limitation of extension. The authors diagnosed and treated five cases of hyperextension overload syndrome. All of them had flexion contracture. Three cases of them had cubitus valgus. But no had medial instability of the elbow. Three cases of them had tenderness on the olecranon tip. Four patients treated by excision of osteophyte or loose body with arthroscopic or open operative technique.

Little Leaguer's Elbow report of 4 Cases / 대한정형외과학회잡지

Repeated throwing of baseballs by juvenile pitchers is known to cause damages to bone and cartilage as well as soft tissue in the involved upper extremity. Authors present 4 cases of osteochondral lesion at capitellum of the humerus as a result of repeated insult by throwing baseballs in the juvenile pitchers. Pain and limitation of extension of the affected elbow were the commonest symptoms. Cystic change or osteochondral loose body was found on plain X-ray. Treatment consisted of rest and analgesic administration in the patient who has no loose body, while in case of having loose body it was removed surgically without further treatment to the crater. In spite of the rapid relief of the pain by these treatment, limitation of extension persisted for considerable period of time. It is strongly suggested not to overlook elbow pain in young adolescent whose bone is still growing and who can hardly withstand repeated insult to prevent the development of baseball elbow.