THE LONG TERM ATHLETE DEVELOPMENT PLAN AIMS TO:
A Message from Joseph Myers Lead Author of the USA Baseball LTAD and Director of Baseball Performance Science for the Tampa Bay Rays
As the primary steward for the sport in the United States, USA Baseball recognizes and embraces the powerful impact that the sport has on players and fans across their lifespan. Given its role as the governing body of the game, USA Baseball sought to develop a Long-Term Athlete Development Plan (LTAD) that is rooted in scientific literature, in order to provide a roadmap for players, parents, coaches, and administrators to participate, instruct, and govern the sport of baseball. An interdisciplinary working group of leading sport scientists with expertise in coaching, strength and conditioning, neuromuscular control, biomechanics, motor learning, injury prevention, sport psychology, and clinical care of athletes was assembled to develop an evidence-based LTAD aimed to:
On behalf of the working group, we feel fortunate to have had the opportunity to collaborate with leaders from all across amateur baseball, in order to provide the scientific content to this important project. This collaboration resulted in a program that provides players, coaches, parents, and fans, with a positive, fulfilling experience where talents can be maximized, healthy levels of fitness can be achieved, and ultimately the sport of baseball can be enjoyed for their entire lifetime.
Joseph B. Myers, PhD, ATC LTAD Working Group Chair Director of Baseball Performance Science, Tampa Bay Rays Baseball
A message from Baseball Africa
While acknowledging that The Long Term Athlete Development Plan (LTAD) was developed by USA Baseball, with support from Major League Baseball (MLB) to provide a multi-stage developmental pathway for an individual’s life-long experience within the sport of baseball in the United States, the findings are too valuable not to share with a wider audience.
Despite the encouraging growth of baseball in Africa, the continent simply does not have access to the wealth of resources and experience that participated in the USA Baseball collaboration. Given the magnitude of this plan and the shared vision to grow the game of baseball in under served areas of the globe, it was in the interests of baseball to share this project with the stakeholders on the continent. Input was received from African stakeholders on the minor Africa-specific revisions to the plan. Access to the unedited original plan is also provided.
USA Baseball, with support from Major League Baseball (MLB), has generated a Long Term Athlete Development Plan (LTAD) to provide a multi-stage developmental pathway for an individual’s life-long experience within the sport of baseball in the United States.
This information is provided because it is equally applicable to baseball in Africa.
• J.D. DeFreese, PhD (University of North Carolina at Chapel Hill)
• Lindsay DiStefano, PhD, ATC (University of Connecticut)
• Avery Faigenbaum, EdD, FACSM, FNSCA (The College of New Jersey)
• Elizabeth Hibberd, PhD, ATC (University of Alabama)
• Joseph B. Myers, PhD, ATC (Tampa Bay Rays Baseball)
• James Onate, PhD, ATC, FNATA (The Ohio State University)
• Brett S. Pexa, MA, ATC (University of North Carolina at Chapel Hill)
In addition to the Working Group, the LTAD was reviewed and edited in part by:
• Carlo Alvarez- Former Director of Sports Performance
• Kyle Boyer- National Development Director, USA Field Hockey
• Rob Butler- Director of Performance, St. Louis Cardinals
• Perry Castellano- Strength and Conditioning Coordinator, Minnesota Twins
• Jon Coyles- Vice President, Drug, Health & Safety Programs, Major League Baseball
• Michael Cuddyer- USA Baseball Sport Development Contributor; Former Major League Baseball player
• Keith Dugger- Head Athletic Trainer, Colorado Rockies
• Darren Fenster- USA Baseball Sport Development Contributor; Minor League Manager, Boston Red Sox
• Elliot Hopkins- Director of Sports, Sanctioning and Student Services, National Federation of State High School Associations
• Brendon Huttmann- Major League Strength and Conditioning Coach, Pittsburgh Pirates
• David James- Vice President, Youth Programs, Major League Baseball
• Dean Jordan- USA Baseball Sport Development Contributor; Managing Executive, Global Sports Media Rights at Wasserman Media Group
• Matt Kata- Manager, Youth Baseball Development and Initiatives, Cleveland Indians
• Eric Kibler- USA Baseball Sport Development Contributor; Retired Head Coach Horizon High School; Arizona High School Athletic Coaches Hall of Fame Member
• Andre Lachance- Sport Development Director/Women's National Team Manager, Baseball Canada
• Chris Marinak- Executive Vice President, League Economics & Strategy, Major League Baseball
• Del Matthews- Senior Director of Baseball Development, Major League Baseball
• Tim Maxey- Strength and Conditioning Coordinator, Major League Baseball and the Major League Baseball Players Association
• Darrell Miller- Vice President of Youth and Facility Development, Major League Baseball
• Kim Ng- Senior Vice-President for Baseball Operations, Major League Baseball
• Tony Reagins- Senior Vice President for Youth Programs, Major League Baseball
• Skip Schumaker- USA Baseball Sport Development Contributor; Former Major League Baseball Player
• Dan Schuster- Director of Coach Education, National Federation of State High School Associations
• Mickey Shupin- Specialist, International Game and Market Development, Major League Baseball
• Morgan Sword- Vice President of League Economics and Strategy, Major League Baseball
• Jon Torine- Sports, Physical Education, Health and Safety, Functional Movement Systems
• Dave Turgeon- USA Baseball Sport Development Contributor; Coordinator of Instruction, Pittsburgh Pirates
• Ricky White- Strength Coach, Pittsburgh Pirates
Baseball continues to be one of America’s most prominent sports, commonly referred to as their“national pastime.” On the professional level, baseball is a staple of many American lives from April to October every year. Within the amateur ranks, the Sports and Fitness Industry Association’s Single Sport Participation Report on Baseball concluded that 14,760,000 athletes engaged in baseball in 2016. However, the recent trajectory of amateur participation remains inconsistent.
In 2014, USA Baseball conducted an audit of the amateur marketplace and identified several challenges facing the amateur game. Most acutely were the lack of coaching education, lack of structured guidance throughout a player’s childhood and adolescence, and the increasing costs of participation. Additional challenges included early single sport specialization, year-round play, and the disproportionate ratio between development and competition.
USA Baseball, with support from Major League Baseball (MLB), has generated a Long Term Athlete Development Plan (LTAD) to provide a multi-stage developmental pathway for an individual’s life-long experience within the sport of baseball in the United States
The Long-Term Athlete Development Plan (LTAD) process forces us to critically scrutinize the changing landscape and examines what needs to be done to better position the sport moving forward. This LTAD is influenced by the work of Istvan Balyi and is the culmination of extensive scientific research on childhood development by experts in the field. We believe that the integration and implementation of this LTAD into the baseball culture across Africa will not only help to get our youth onto the fields, but also positively impact their overall experience within the sport. Consider this:
This LTAD has been generated by USA Baseball, with support from Major League Baseball (MLB), (with minor Africa-specific revisions), to provide a multi-stage developmental pathway for an individual’s life-long experience within the sport. The LTAD plan is a culmination of evidence-based information from the principal contributor group and input from a leadership group consisting of experts from the medical safety industry, MLB league and club executives, and an advisory group inclusive of leaders from across the amateur baseball spectrum. This document has been most directly prepared for the main influencers in an athlete’s life including but not limited to parents, coaches, league administrators, teachers, and the athletes themselves.
The Long-Term Athlete Development Plan:
The LTAD recognizes the need to involve all Africans in the developmental pathway, not just the elite athletes, and is made up of a seven-stage framework. Each stage is categorized by a chronological age group, however, an athlete’s skill level may not align with his or her chronological age. Therefore, the skill sets of the individual athlete need to be assessed to determine his or her pathway needs. An athlete can enter into the pathway at any point through his or her progression. In doing so, it may be beneficial to pull recommendations from previous stages of development. Athletes will continue to progress and develop within each individual stage, but the objectives are the underlying drivers of the stages. This framework also allows for athletes to begin an “Advanced Track” within the Develop Stage for 14- to 16-year-olds. Advanced athletes are those who show a high level of aptitude in the sport at their given age. The “Advanced Track” is a pathway of development that allows for elite athletes to dedicate more direct time and energy to training and competition for their high-level progress in the game.
USA Baseball, which as the national governing body for the sport in the United States, draws on these key principles when developing initiatives such as the LTAD.
The LTAD utilizes common terms throughout each stage. The major components for each stage are defined as follows.
This document serves as a long-term athlete development plan for the sport of baseball. As a multistage pathway for training, competition, and recovery, the LTAD guides an athlete’s experience in sport and physical activity. Through developmentally appropriate programs for all ages, the LTAD aims to increase participation and optimize performance across the sport of baseball.
Foster a love for the game by introducing children to the sport of baseball through styles of gameplay that promote fun, creative play and success. Athletes in this stage should be developing basic movement and motor skills via sport sampling. Baseball should also be a means for developing friendships and encouraging other positive peer interaction. Proper warm up and cool downs should be part of the sport experience.
Periodization and Competition:
Basic baseball skills are being fostered and in some cases honed. Athletic movement should become more advanced as speed, agility, balance and general coordination all improve. Athletes should be in an environment where they learn to be motivated to succeed, while continuing positive social development amongst teammates and competitors. Sport sampling and informal or deliberate play continue to promote well-roundedness. Injury awareness, including arm care should be present for the athlete, their coach and parents.
Periodization and Competition:
Skill training is now becoming more specific and should include mechanical elements and awareness. Athletes should be self-motivated and will begin understanding how to self-diagnose aspects of their training and performance.
Physical development should be technique driven and age appropriate, and overall wellness should include proper arm care planning. Competency (success or self-improvement) is important in this stage, as is a continued multi-sport approach. While competitive play will increase, more time should still be spent training proportionately.
The athletes physical and skill development should become increasingly individualized and should cater to their own growth and be specific to their preferred position(s). Safe training practices should be maintained, and rest and recovery after workouts, practices, and games remain imperative. Fostering a positive social environment that includes opportunity for self-determination for the athlete, and open communication between the athlete, parents and coaches will aid in success on and off the field. In appropriate instances, specialization may occur in this stage, but multi-sport athletics are still encouraged.
Athletes who demonstrate an advanced level of development within the sport may wish to further dedicate themselves to their progression towards the upper echelons of the game. While maintaining a well-rounded approach, athlete training should further focus on position specific skills and mechanics. Baseball specialized athletes may spend added time throughout the year training and competing but should be even more alert to overuse related injuries, especially connected to throwing. Mentors should be aware that while these athletes may be gifted in sport, they are often on par with their peers’ mental and social development. See “Develop” stage for additional markers.
Training and practices should be working towards team and individual optimization. Athletes should be able to uses elf-observation to identify mechanical and other skill deficiencies. Strength and conditioning activities should be athlete specific and should maintain an approach that ensures total body fitness, muscular strength and motor skill competency. Athletes should maintain an individualized arm care program, especially as the amount of competition increases over time. Single sport specialization among advanced athletes may occur. The promotion of positive developmental environments within teams and personal training settings remains important.
Advanced level athletes within this stage are those who are likely to graduate to the Excel stage, and will play either at the collegiate or professional levels. While those outcomes may motivate the athlete, a process- based development plan should be maintained that promotes a well-rounded approach to the physical, mental and social sides of the sport.
Single sport specialization in this stage is more likely to occur, although it is not mandatory for baseball advancement. Increased competition levels, mean an increased focus should be paid to total body wellness and arm care. Skill specific training should be advanced with the athlete possessing a base of knowledge in individual and situational play. See“Apply” stage for additional markers.
Athletes in this stage are maximizing their physical, psychosocial, and skill specific preparation and performance. Mastery of all individualized mechanical functions and team related situational plays are being worked on as a daily occurrence in practice and in games. Physical competencies should be optimized with athletes training to move and think at levels approaching their personal best. Coaches within this stage should be experts within their specific field. Single sport specialization is highly likely, but other recreational sports can aid in overall well-being as allowable. Position specific training and nutritional guides should be implemented to support the challenging practice and competition schedules athletes will endure.
Periodization and Competition:
This stage of development can be accessed at any point after the Activate stage. Those who inspire within the game continue to participate in a bat and ball sport to foster a healthy lifestyle. Athletes should remain involved in any capacity, whether it is as a player, coach, umpire, or volunteer. Participation in gameplay either at baseball recreational levels or on the softball field is encouraged. Developing a love and mentoring future generations through positive experiences in baseball allows athletes to pass on the many great life lessons learned through the game.
Baseball offers a valuable opportunity for individuals to be physically active across a lifespan. For children, baseball provides a unique exposure to a variety of fundamental movement skills that can be transferred to other sports and activities to ensure physical literacy, the ability to play other sports, and long-term athletic development. Physical literacy is frequently defined as the ability to move with competence and confidence during different types of physical activities. In order to optimize growth and athletic potential, baseball instruction should be tailored to the developmental ability of each child. Children develop mastery of movement control, or sport ability, at different rates and stages of maturation. This is critical to understand because without this mastery of basic fundamental skills, children may not progress in the sport or skill, become injured, and/or choose to leave baseball, and possibly all sports.
The term “fundamental movement skill” is frequently used to describe common motor activities that are the underlying framework for basic movements and complex sport and movement skills. Examples of these fundamental movement skills include walking, running, jumping, hopping, skipping, catching, and throwing. Physical and cognitive maturation are important for the development of these skills, but the environment via practice opportunities and social encouragement also influence whether or not these skills are effectively developed (8). As fundamental skills are attained, they are gradually combined and progressed to become more advanced sport skills (8). Sometimes children have difficulty acquiring these skills and these problems may differ between individuals, but are usually due to incomplete modeling of movements of other individuals, initial success with an incorrect movement, lack of motivation, inappropriate or scarce learning opportunities, or problems with sensorimotor integration (8).
In comparison to other sports, baseball has a unique ability to help children develop a wide variety of fundamental movement skills based on the nature of the sport. For example, catching, running, jumping, overhand throwing, leaping, dodging, forehand strike and two-hand side-arm strike are all fundamental motor skills that can be addressed during baseball. Once mastered, these fundamental movements can be further advanced into sport-specific skills, such as throwing, batting, sliding, diving, and shuffling during baseball. A child needs to be able to strike a stationary object (tee-ball) consistently before moving to a moving object (coach pitch). Mastery of fundamental movements is critical for all children because it is associated with physical activity participation and improved health and well-being in children (8, 9).
Physical education is not compulsory for all children or a large part of many children’s education curriculums. Consequently, if not for sport, many children will not be taught these skills by anyone. Gallahue (8) noted this failure in skill development might be because many people believe children will automatically learn these fundamental skills and do not need to be taught. Acquisition and development of fundamental motor skills needs to be an important objective of society, because possessing these skills leads to improved physical activity levels and increased participation in games and sports. (8, 10, 12) A failure to reach competency in a variety of the fundamental motor skills will cause limited proficiencies of sport specific skills (8). Youth participation in developmentally appropriate sport activities has been recommended to encourage future participation in sports and physical activity throughout a lifetime (8, 11).
An important consideration that baseball instructors should understand is their role as “teachers of movement or skill development.” Coaches and parents need to be involved in the process of skill acquisition and athletic development, not as passive instructors. Coaches and parents need to understand what is appropriate technique and movement quality, as well as how to provide effective instruction and feedback. The ability for a baseball instructor to understand the role of the motor learning process for movement skill acquisition is paramount to being able to provide quality coaching for baseball athletes of all ages.
The main difference between learning and performance is that learning is considered to be relatively permanent and stays relatively constant over time. Performance, on the other hand, is the behavioral act of executing a skill at a specific time in a specific situation. In the baseball instruction setting, an example of the distinction between performance effects and learning effects can be seen when evaluating a ballplayer’s hitting capability. An immediate batting instruction goal could be for the batter to hit line drives to the opposite field. The instructor has the ballplayer perform numerous drills to influence the ballplayer’s ability to hit line drives to the opposite field. At the end of the session, the instructor sees the ballplayer leave the field being able to consistently hit line drives to the opposite field with sound hitting technique. The question here is: Has the ballplayer acquired a good swing pattern that transfers to learning to hit in real game situations or is the ballplayer just performing well during practice drills? The answer cannot be known because the only assessment of performance was done during the practice situation, which involved assistance from the instructor. The more critical analysis should take place later on in the day or over the course of the next few days in a natural game environment (especially in a situation when the ballplayer does not suspect they are being observed and that they should be "performing" proper hitting technique). By making these later observations, the instructor analyzes the retention and transfer effects of the instruction, which is the key markers of learning, rather than the performance effects observed during the practice session. These later observations will allow the instructor to more accurately estimate their success as a "teacher of movement," while also analyzing the ballplayer’s stage of learning the intended skill.
Fitts and Posner (13) described a theory related to the stages of motor learning that people go through when learning a new movement task. They suggested that there are three main stages involved in motor learning: (1) cognitive, (2) associative, and (3) autonomous. The first phase of learning, according to Fitts and Posner, is the cognitive stage of learning. The cognitive stage is associated with the learner initially developing an understanding of the requirements of the movement task and initially developing strategies that can be used to carry out the task. Fitts and Posner (13) theorized that this initial stage required a high degree of cognitive activity (e.g., attention, memory) and that a learner often experiments with a variety of movement strategies resulting in large movement variability. The cognitive stage is marked with a large amount of variability, but it also is noted for large improvements in learning as a result of the beginning stages of learning.
The second phase of learning, according to Fitts and Posner (13), the associative stage, is when the learner has selected the best strategy for movement from the cognitive stage and now begins to refine the movement skill. The variability in performance tends to decrease in the associative stage and improvement also occurs at a much slower rate. The associative stage may vary in duration (e.g., days, week, or months) and is dependent upon both skill and learner characteristics.
The final stage of motor learning, according to Fitts and Posner (13), is the autonomous or "automatic" stage. The final autonomous stage is defined by Fitts and Posner (13) as the "automaticity of skill" and requires little attentional demand for performance. In the final stage of motor learning, Fitts and Posner (13) state that learners can begin to devote their attention to other aspects of the movement (e.g., recognizing and hitting a curveball to the opposite field or seeing a runner break for home plate while preparing to field a ground ball). Individuals may move between the associative or autonomous stage dependent on numerous motor skill learning parameters (e.g., practice schedule, feedback, task demands), thus an individual can always enhance or reduce the automaticity of the movement task and attempt to achieve consistent optimal movement skills (e.g., baseball pitching, hitting, fielding). Caution should be taken, as repetition of the exact same movement pattern might cause suboptimal learning compared to allowing the utilization of movement pattern variation, which stimulates the nervous system to create optimal solutions for unanticipated events more effectively (14). A combination of directed practice and variability in movement patterns is optimal for learning new skills.
Instructions from coaches/parents oftentimes start off with information focused on internal aspects of movement (e.g., keep elbow higher, move feet wider, and snap your wrist). These aspects of instruction are termed internal focus of attention and can help to start the guidance of movement, but oftentimes fall short in longer-term motor learning.
Conversely, drawing a learner’s attention towards an outcome or effect of the movement (e.g., pull the cloud down as you throw, exchange your shoulders as you swing through the ball, land light as a feather when stepping to swing) are considered external focus of attention instructions which have demonstrated improved motor learning capabilities in the long-term. Review of the motor learning research has shown that external focus of attention instructions helps to accelerate the initial stages of the learning process by facilitating the development of movement strategies to produce effective movement patterns (15, 16). A typical external focus of attention concept utilization in baseball is the use of a batting tee for hitting mechanics. The external focus of the swing is to hit the ball on the tee towards the opposing team as contrasted to an internal focus of attention concerning hand and elbow placement in swinging a bat. Initial learners can be guided through visual feedback, but oftentimes the physical movement pattern exploration relative to the external focus of attention allows for the learner to create efficient movement tasks to complete the intended goals. Advanced learners can flow back and forth between internal and external attentional foci, but a majority of the learning process is aided by external focus of attention.
Physical literacy can be defined in many different ways. The Aspen Institute and Project Play defines physical literacy as the ability, confidence, and desire to be physically active for life. The Functional Movement Systems program defines physical literacy as competency, complexity, and capacity for physical activity. Sport Canada has developed the following basic movement skills for all sports as:
Receiving and Sending
While there are increasing opportunities to participate in more competitive sport environments at younger ages, in order to perform at an elite level and withstand the mounting demands of training and competition, young baseball athletes must be prepared for their sport. Inadequate or inappropriate preparation during the initial sport preparation stage contributes to compromised skill development, injury, burnout, dropout and unrealized talent potential (17). Player Development Model frameworks should recognize the multidimensional nature of athletic development and the critical importance of physical fitness for each developmental phase (18, 19). A certain level of force production and force attenuation is required to perform all athletic movements, and therefore preparatory physical development should be considered foundational to long-term athletic development (35). At present, leading fitness and sports medicine organizations support participation in youth physical development programs that are consistent with the needs and abilities of young athletes (20).
Despite global physical activity recommendations, a corollary of modern day lifestyles is a lower level of muscular fitness and motor skill competency among school age youth (21-23). Without preventive measures that target deficits in muscular strength, a growing number of aspiring young athletes may not be prepared for the demands of sports practice and games (24). Since participation in organized youth sports does not ensure a suitable level of general fitness that is consistent with sustainable performance at an elite level (25, 26), a structured and progressive approach is needed to develop movement skill competency and muscular strength in young athletes. Clearly, participation in youth baseball should evolve out of general preparatory conditioning and instructional practice sessions that enhance general physical fitness.
Sport participation with strength and conditioning can enhance athletic performance, reduce the incidence of sports related injuries and improve markers of health (19, 20, and 27). Stronger young athletes will be better prepared to learn complex movements, master sport tactics and withstand the demands of long-term sports training and competition (19). From a public health perspective, early exposure to strength and conditioning that emphasize the development of muscular strength and movement skill competency can serve as a foundation for regular participation in physical activity as an ongoing lifestyle choice (18, 35, and 29).
In order to foster positive physical development, maintain adherence to the training programs and optimize long-term adaptations, youth strength and conditioning programs should be sensibly progressed and manipulated over time. Young baseball athletes who are not exposed to this type of training will inevitably need to address technical flaws and neuromuscular deficiencies as part of injury rehabilitation or athletic development later in their sport careers. Moreover, young athletes who engage in intensive year-round training in one sport early in life are more likely to suffer sports-related injuries (30). There is an unparalleled opportunity early in life to target strength development and promote multisport participation to set the stage for enhanced athletic development later in life.
Effective and integrative approaches to long-term athletic development should include the qualified prescription of strength and conditioning programs that are designed to address individual limitations in an attempt to make youth sport more engaging, enjoyable and safe (17, 31). The direct result of sustained participation in developmentally appropriate strength and conditioning programs is the improvement in a wide range of athletic capabilities. Since a certain level of muscular strength is needed to throw, jump and sprint proficiently, the importance of strength and conditioning for young baseball athletes should not be overlooked. Just like reading and writing, the development of muscular strength and motor skills can be enhanced with regular practice, meaningful feedback and qualified instruction.
Owing to the high degree of neuromuscular “plasticity” during preadolescence, the effects of physical development on motor skill performance appear to be more pronounced in children than adolescents (32, 33). Consequently, young baseball athletes need regular opportunities to develop sufficient levels of muscular strength and movement skill competency. The dynamic relationship among muscular strength, motor skill proficiency and athletic performance will likely be reinforced over time, which is consistent with the existence of a positive feedback loop. Without opportunities to gain confidence and competence in their physical abilities early in life, young athletes will be less likely to reach their athletic potential later in life and more likely to experience negative health outcomes.
Training-induced adaptations to physical development are influenced by the neuroplasticity at each stage of development, in addition to the design of the training program and quality of instruction. Different types of strength and conditioning have proven to be effective, although the training intensity and volume are important considerations (34, 35). Significant positive correlations have been found between gains in motor performance skills and the mean intensity (% 1 repetition maximum) of the training program (32). Therefore, once beginners develop proper form and technique with light loads, the amount of resistance should be gradually increased as participants gain confidence and competence in their physical abilities. The minimal dose of training required to elicit the desired effect is different in untrained and trained youth, and therefore it is important to consider each player’s strength and conditioning experience when designing training programs.
Existing research indicates that regular participation in integrative strength and conditioning programs can elicit performance improvements in muscular strength, muscular power, running velocity, change of direction speed, dynamic balance and flexibility in children and adolescents (35,36). Other researchers reported favorable improvements in throwing velocity (41, 42) and torso rotational and sequential hip-torso-arm rotational strength (43) following several weeks of supervised physical development in young baseball athletes. Integrative training includes general and specific exercises that improve muscular fitness and enhance a range of physical qualities including fundamental movement skills (36). Naturally, as muscular strength and skill proficiency improve, the load and complexity of the strength and conditioning program should be consistent with the training experience and technical abilities of young athletes. This is where the art and science of developing youth strength and conditioning programs come into play because the principles of pediatric exercise science need to be balanced with effective coaching in order to enhance a player’s physical, social, cognitive and emotional well-being (28). Inappropriate coaching approaches and extreme conditioning protocols can result in overtraining, injury and burnout. Qualified professionals who are well versed in physical development and skilled in teaching and communicating with young athletes should design and implement youth strength and conditioning programs.
While catastrophic injury in baseball is rare, other less severe injuries have a more common occurrence, even among young athletes. These injuries, such as bruises, cuts, scrapes and other minor injuries are often understood. However, there is significant attention focused on chronic and overuse injuries occurring in the sport of baseball across all age groups. There are many injuries that a baseball player may experience and various mechanisms for how these injuries can occur (91).
For youth baseball injuries, because there is no overall surveillance mechanism to capture exposure, these data are presented as relative frequencies of injuries that have occurred between January 1994 and February 2015. The youth data provided are from accident insurance claims data broken out into two age categories: ages 5-12 and ages 13-19.
These data may reflect more severe injuries as they are from accident claims data, but do describe patterns of injury occurring in youth baseball. These data do not include exposure to risk of injury or overall injury prevalence out of all participants over the course of a season.
In addition to the claims data, literature around throwing related injuries among youth has also suggested that a much higher percentage of youth baseball pitchers are suffering chronic, overuse injuries and having surgery (91).
The high school baseball injury data presented here are a summary of the most recent injury pattern data available through high school injury surveillance systems. As exposure to risk is captured in these types of studies, we are able to estimate incidence rate (how many injuries occur per so many exposures to injury risk) and prevalence (what proportion of the population suffers an injury).
Many baseball injuries are due to overuse of the throwing arm. Monitoring throwing activities, especially among pitchers, may aid in decreasing the relative frequency and occurrence of these types of injuries. There are many valid resources for aiding parents, coaches, and athletes in injury prevention including education programs, pitch count limits, and training programs that may aid in preventing injuries in baseball, these can be found through the Amateur Resource Center and Pitch Smart websites (91).
While all positions present some risk, pitchers account for 73 percent of injuries in high school baseball athletes, of which approximately 38 percent require surgery (37). In a longitudinal evaluation, five percent of adolescent baseball pitchers developed a shoulder or elbow injury that resulted in surgery or retirement from sport (38). In youth baseball, almost half of all pitchers report elbow or shoulder pain at some point during a baseball season (39, 40). With baseball, especially pitching, a large number of injuries and lost time is attributed to upper extremity injuries such as impingement, rotator cuff injury, shoulder instability, labral tears, and elbow ulnar collateral ligament injury (48, 39-45).
Pitching mechanics are critical to injury prevention, independent of pitch type, and considerable time should be spent teaching mechanics that decrease the stress on the shoulder and elbow for both decreased injury risk and improve performance. The pitching motion is a complex movement that generates tremendous force and places significant strain on the soft-tissue restraints of the upper extremity (46).
Interestingly, some of the pitching mechanics that have been reported to increase elbow joint stress also are associated with greater throwing velocity. Specifically, greater shoulder external rotation range of motion was found in collegiate pitchers who were classified as high-velocity pitchers (mean >85mph) compared to low-velocity pitchers (mean <76.5 mph) (47). Greater shoulder external rotation has been hypothesized to increase the stored elastic energy of the internal rotators and improve the stretch-shortening cycle increasing the concentric strength of the internal rotators during the acceleration phase of pitching thus ultimately increasing pitching velocity (47). In addition, excessive contralateral trunk tilt has been associated with greater pitching velocity (47). The authors of this study suggest that with increased contralateral trunk tilt indirectly increases maximum shoulder external rotation, which results in a greater pitching velocity. Continued research is needed in order to maximize performance, while minimizing injury risk.
Davis et al (48) identified 5 parameters that can be evaluated on video analysis: leading with the hips, hand on-top position, arm in throwing position (elbow at max height at stride foot contact), closed-shoulder position, and stride foot toward home plate. Youth pitchers who perform three or more of these parameters correctly display lower elbow valgus load, thus decreasing the stress on the UCL and lower humeral internal rotation torque decreasing stress on the shoulder passive and dynamic restraints (48). In addition, serial evaluations at all levels of baseball can also serve as indicators of changes that are occurring in the pitching motion due to fatigue or injury and may provide valuable information to the coach and clinician.
Repetitive throwing causing microtrauma without adequate time for recovery has been proposed as a risk factor for upper extremity injuries (39, 49, and 50). High pitch counts are often blamed for injury in the media and among parents of younger athletes. In youth baseball athletes, higher pitch counts have been associated with increased risk for shoulder and elbow pain (39, 40). Olsen et al (51) saw that higher number of warm-up pitches, more innings pitched per game, more pitches thrown per game, and pitching eight or more months out of the year were associated with a higher risk of elbow injuries in youth baseball pitchers. In a group of 9-12 year old pitchers, the risk of should pain increased 15 percent for every 10 additional pitches thrown and pitchers who threw more than 75 pitches per outing were three times more likely to experience shoulder pain those who pitched 1-24 pitches (40). The risk of elbow pain increased six percent for every 10 pitches thrown, and pitchers who threw more than 75 pitches per outing were 1.5 times more likely to experience shoulder pain those who pitched 1-24 pitches (40).
The USA Baseball Medical and Safety Advisory Board and American Sports Medicine Institute combined research evidence with clinical expertise to create participation recommendations for youth and high school baseball athletes in the Pitch Smart Guidelines (52). These guidelines specify outing pitching limits, as well as rest and recovery periods. Work by USA Baseball Medical and Safety Advisory board and American Sports Medicine Institution have identified outing, weekly, and season guidelines for youth and adolescent baseball athletes (53, 54). These organizations also recommend that youth pitchers have inning restrictions in a year and take at least two to four months off from baseball participation each year. It is imperative that parents and coaches track the number of pitches that their athlete is throwing. These guidelines are of cumulative load and are not team specific.
Participating in baseball across the lifespan represents a key activity that can promote lifetime physical fitness as well as psychosocial development. When approached properly, baseball athletes can gain much from lifelong participation including development of: 1) social skills and peer relationships, 2) physical competence and psychological well-being and3) enjoyment of and intrinsic motivation for participation in competitive and/or recreationally baseball for a lifetime. When considering a player’s maturation within the sport, efforts should be made to prevent burnout and minimize dropout so young athletes may gain these benefits. Beyond injury prevention and maturation concerns discussed in other sections, baseball specialization decisions should be made thoughtfully relative to psychosocial well-being based on the guidelines described below.
More self-determined forms of motivation are driven by individual choice rather than from internal pressures, like guilt, or external pressures such as reward, punishment or expectations from others. Intrinsic motivation, participation in the sport/activity because of love/enjoyment of it, is the most self-determined form or motivation. Therefore, efforts to promote either intrinsic motivation or more self-determined motivation can promote psychosocial well-being for athletes. Self-determination theory (SDT) further explains motivation to be influenced by the psychological needs of autonomy (personal choice or control), competence (success or effectiveness in one’s environment) or relatedness (social connection to others, acceptance, belonging). When athletes feel these needs are met within their social sport environments more self-determined, and potentially intrinsic, forms of motivation are expected. Such feelings could be instilled in athletes by behaviors and strategies utilized by coaches, parents, administrators or teammates to help satisfy these needs. This leads to the most adaptive psychosocial outcomes for athletes. SDT provides an extremely useful framework to guide this section because it highlights key environmental factors, which can be changed to enhance athlete motivation, psychosocial health and, ultimately, long-term sport involvement.
Sport represents an environment where feelings of competence can impact youth and adolescent self-esteem (55). Sport commitment represents a key means by which to understand athlete sport experiences including healthy participation as well as more negative outcomes like burnout or dropout. Researchers (56) proposed that outcomes of burnout and dropout result from athlete feelings regarding the rewards and costs of sport participation when accounting for enjoyment level and attractiveness or other sports or activities. Using this theory, a sport scientist (57) examined patterns of athletic identity and commitment and found that athletes reporting higher burnout scores, reported lower sport enjoyment, fewer benefits, fewer attractive alternatives to sport and less control over their sport experience. They also reported higher sport costs, more investments, higher social constraints (demands) and a unidimensional sport identity. Though not all athletes experiencing this pattern of commitment will burn out and ultimately dropout. Preventing such a pattern could promote more positive athlete sport experiences and prevent dropout. Promoting a more positively social environment including athlete enjoyment and developing of other aspects of athlete identity beyond sport could facilitate this aim.
Athlete burnout is one of many psychological health variables that should be considered when promoting the health and well-being of athletes. Athlete burnout is characterized by emotional/physical exhaustion, reduced accomplishment and sport devaluation (58). One reason that burnout is so important to prevent/manage is that it is associated with other key variables of sport participation. An integrated model of athlete burnout (59) explains that burnout is associated with described (57) maladaptive patterns of sport commitment, sport stress, mood disturbances, low social support, low sport autonomy and coping skills, and is influenced by the motivational climate (i.e., coach or other environmental influences) associated with sport training/competition. Thus, positively influencing any of these variables could serve to prevent burnout as well as sport stress and potentially mood disturbances. Research supports that coping behaviors are negatively associated with burnout (60) and, therefore, could be promoted as a means to manage or prevent the occurrence of symptoms. Moreover, social support from teammates may represent a key factor in ensuring burnout and stress prevention as a means to promote athlete psychosocial well-being (61). Education about important aspects of psychological health, including sport stress, athlete burnout and mood-related outcomes in sport (depression, anxiety) further serves to aid in their prevention. Beyond individual athlete efforts, coaches, parents and administrators also have potential to positively influence athlete psychological health and well-being.
Guided by theory, research and clinical judgment, the sport-based social environment can be utilized to positively impact the development of athlete social and motivational experiences. Coaches represent a key member of this environment with the ability to positively influence athlete psychosocial health and motivation. Autonomy supportive coaching behaviors, including training decisions, how feedback is provided and coaching style, have been shown to positively influence athlete self-determined motivation (62) and psychological needs of autonomy, competence and relatedness (63). Thus, coaches have potential to positively impact athlete motivation and psychological health by utilizing facets of autonomy supportive coaching. Mageau and Vallerand (64) have described examples of autonomy supportive coaching behaviors including: 1) providing athletes choices within coach-directed rules and limits, 2) providing athletes a rationale for tasks and limits, 3) acknowledging athletes’ feelings and perspectives on key issues, 4) providing athletes with opportunities for initiative taking, 5) providing feedback which supports athlete competence, 6) avoiding unnecessary criticism and controlling statements and behaviors, and 7) promoting task/mastery -involvement and preventing ego involvement among athletes. Involved parents could benefit by using similar strategies relative to the baseball participation of their children. Ultimately, autonomy supportive behaviors directed towards Baseball athletes will have important positive implications for burnout prevention, as well as for the psychological health and well-being of baseball athletes across the lifespan.
From the perspective of individual athletes, psychological skills training (also known as mental skills training) represents an important tool to deter sport stress and other negative psychological outcomes (burnout) and promote positive outcomes of psychological health (motivation, enjoyment) and performance. Psychological skills include goal setting, arousal-regulation, visualization/imagery, concentration/mindfulness techniques and coping skill development, among others. Education on the basics of such techniques can be provided from a variety of sources including trained coaches or administrators, particularly at very young ages. However, advanced training, implementation and evaluation of psychological skills programs for athletes should be conducted by a certified sport psychology consultant and take into account developmental differences based on the ages of the athletes being worked with (65). Clinical issues related to athlete mental health (e.g. clinical anxiety or depression, substance use) require work with an appropriately clinically trained and licensed psychologist or psychiatrist. Collectively, psychological skill development represents an important means to positively impact athlete psychological health and well-being and potentially facilitate optimal performance. It is important to remember that just because youth athletes look like (and occasionally act like) small adults does not mean that they are adults. They still think like children/adolescents and their thoughts regarding their early sport experiences may not be the same as those of their parents/coaches. Accordingly, their psychosocial health should be monitored appropriately whether they choose to specialize in baseball or not. These efforts will involve inclusion of
administrators, coaches, parents and athletes themselves.
Sports specialization is defined as near year round (typically greater than 8 months per year), intensive training in a single sport, and excluding participation in other sports (6, 67, 68). While single sport specialization can be a pathway to achieve elite status (67-70), early sport specialization is also linked to player burnout (4, 7, 71-75) and increased injury risk (4, 67, 68, 71, 72, 74-79) often leading many athletes to cease participation in the game (4, 5, 7, 67, 69, 71, 74, 76, 80-85). Thus, early specialization is not conducive to fostering talent while promoting lifelong participation and enjoyment of the sport of baseball (67, 68).
One of the most pressing issues relative to athlete psychosocial health is sport specialization (66). From a psychosocial standpoint, discouraging specialization until athletes mature cognitively and emotionally supports healthy social and identity development via exposure to multiple sport environments (e.g., coaches) and social groups (e.g., teammates). Thus, specialization should be discouraged until at least age 14. Beyond this age, specialization could be permitted, though it should be carefully monitored and never be required of an athlete (but rather be the result of a decision the athlete is actively involved in making). For ages 14 and older, specialization will not necessarily harm social or identity development; but at the same time, is not necessary to facilitate peak performance and should be monitored carefully. To allow for healthy social and identity development as well as to prevent low motivation, burnout and ultimately dropout, specialization should be permitted (but not required) for baseball athletes who are physically and mentally prepared to do so.
There is a misconception that the only way athletes become elite in any sport is through early specialization. It has been recognized that there are two pathways to achieve a high level of performance: through early specialization and through early sampling (1). All sports can be classified as either early or late specialization. Early specialization sports, such as gymnastics, diving, and figure skating, take a great deal of specific training and development to succeed. However, most sports are late specialization sports. Baseball, football, basketball, and soccer all fall into the late specialization category.
The difference between the two is that early specialization sports require complex skills to be learned before maturation since they cannot be mastered if taught afterwards, whereas late specialization sports allow for athletes to learn sport specific skills at later ages.
While early engagement in baseball is encouraged, specialization should not take place until athletes are developmentally matured. Specializing too early in a late specialization sport can lead to:
Contrary to early specialization, early sampling focuses on aiding in the general developmental needs of children through participation in many different activities (1). This allows children to engage in a wide range of physical movements that may not be able to be developed as well during sport specific training.
Children are encouraged to participate in and sample multiple sports during their important developmental years (from entry into the sport through at least age 14) rather than specializing in a single sport. Sampling involves both participation in multiple sports and focusing primarily on deliberate play when participating in those sports. While deliberate play should be the emphasis, some deliberate practice (conducted in a manner that contributes to sport performance), should be included to contribute both skill building and physical fitness.
Sampling as an alternative to single sport specialization has been shown to facilitate athletic prowess and ultimately obtaining elite status as well as often requiring less sport specific practice to acquire expertise (86). Partaking in a variety of sports allows participants to experience a number of different physical, cognitive, affective, and psychosocial environments, and experience different social interactions with peers and adults (76, 83, and 87). Additionally, early sampling followed by eventual specialization leads to more sport enjoyment, lower injury risk, and longer participation (73, 80, and 85). Finally, taking a deliberate play sampling approach during childhood resulted in increased physical activity as an adult, thus foster lifelong engagement and physical activity (88). Ultimately, early diversification and sampling is linked to longer sport career and long-term sport involvement (89).
A large part of early sampling is deliberate play. Deliberate play is defined as an activity that is intrinsically motivating and is meant to be enjoyed, such as playing whiffle ball (2). These activities allow for children to try a variety of movements while learning how to handle different athletic situations (1). Early specialization programs infrequently incorporate deliberate play, which can be detrimental to an athlete. Instead, early specialization programs focus on deliberate practice, which are extrinsically motivated activities focused on sport-specific skill acquisition that can lack enjoyment, like repetitively fielding groundballs (2). Research has shown that deliberate play between the ages of 6-12 correlates positively with baseball specific training after the age of 13, while the high volume of deliberate practice in early specialization programs lead to higher dropout rates (1).
Evidence exists that suggests early sampling is an effective method to reach elite levels in baseball. A study published in The Journal of Clinical Sport Psychology supports that early sampling is a strong pathway to take for athletes (1). The voluntary study surveyed 708 minor league professional baseball athletes that were trying out for their major league team during spring training. It was found that these athletes, who had a mean age of 22.85, played an average of 2.48 sports during the ages of 11-14 (1). While 98% of the athletes surveyed during this age range played baseball, it was observed that the mean age that athletes specialized in baseball was 15.52 (1). The combination of playing multiple sports at a young age and waiting until the 14-16 developmental age years to specialize in baseball allowed for these athletes to see success later on within the professional level.
7. Periodization and Competition
Periodization refers to the timeframes that are used to schedule training, competition, and recovery. Periodization structures the training components into weeks, days and sessions, and is situation-specific, depending on priorities and the time available for training and competition improvement. In the LTAD context, periodization connects the stage the athlete is in to the requirements of that stage.
The balance of training and competition, or deliberate play and deliberate practice, is crucial in each stage of the LTAD. Deliberate play is defined as developmental physical activities that are intrinsically motivating, provide immediate gratification, and are specifically designed to maximize enjoyment (2). Deliberate play activities typically occur between the ages of 6 and 14, and include classic neighborhood pickup games, such as backyard baseball and street basketball. These games are usually comprised of small-sided teams with flexible, peer-defined rules. Deliberate practice is defined as highly structured practice undertaken with the specific purpose of improving performance. In addition, deliberate practice is characterized as requiring sustained cognitive and/or physical effort, being solely directed toward positive skill development and error correction, and not necessarily being inherently enjoyable (2).
Appropriate use of periodization and competition can aid in building confidence in athletes at all levels. The ratios of time dedicated to deliberate play to time dedicated to deliberate practice differ in each developmental stage to allow for an increased opportunity for success. The younger stages, such as Activate and Discover, should be training (or participating in deliberate play) for 75 percent of the time, over one to two days per week in season. Young athletes should be permitted to participate in deliberate play as much as possible with the focus of fostering confidence, ability, and desire to participate in physical activity. Over-competition and under-training in these stages can result in a lack of basic skills and fitness.
After the age of 14, athletes can begin to specialize and move to the elite track. In this scenario, athletes in the Develop, Apply, Excel and Inspire stages can begin to shift to more deliberate practice and competition time versus deliberate play. Specifically, the Excel and Inspire stages will depend on the level of competition the athlete is involved in, such as collegiate baseball in Division I, II, III, or junior college, or professional baseball.
While schedules are often set for baseball by leagues and organizations and not by the coach and athlete, making optimal training based on periodization difficult, it is important to remember that the level and length of the competitive season should be aligned with the changing needs of the developing athlete progressing through the LTAD.
The Long-Term Athlete Development Plan is a vehicle for change in the way baseball is designed and delivered. It is athlete-centered from the moment a child is first introduced to the sport and includes the development of that child through adulthood. While no two athletes are exactly alike, this LTAD provides a pathway and general guidelines for optimal performance based on the various stages within an athlete’s development.
(1) Ginsburg, R. D., Danforth, N., Ceranoglu, T. A., Durant, S. A., Robin, L., Smith, S. R., and ... Masek, B. (2014). Patterns of Specialization in Professional Baseball Players, Journal of Clinical Sport Psychology, 8(3), 261-275.
(2) Berry, J., Abernethy, B., and Cote, J. (2008). The Contribution of Structured Activity and Deliberate Play to the Development of Expert Perceptual and Decision-Making Skill, Journal of Sport and Exercise Psychology, 30, 685-708.
(3) Physical Activity Guidelines for Americans. (n.d.). Retrieved from http://health.gov/paguidelines/
(4) Malina RM. Early sport specialization: roots, effectiveness, risks. Curr Sports Med Rep. 2010;9(6):364-71. doi: 10.1249/JSR.0b013e3181fe3166. PubMed PMID: 21068571.
(5) Mostafavifar AM, Best TM, Myer GD. Early sport specialisation, does it lead to long-term problems? Br J Sports Med. 2013;47(17):1060-1. doi: 10.1136/bjsports-2012-092005. PubMed PMID: 23258850.
(6) Myer GD, Jayanthi N, DiFiori J, Faigenbaum AD, Keifer AW, Logerstedt D, Micheli L. Sport specialization: Part 1:Does early sports specialization increase negative outcomes and reduce opportunity for success in youngathletes? Sports Health. 2015:(in press). doi: 10.1177/1941738115598747.
(7) Smucny M, Parikh SN, Pandya NK. Consequences of single sport specialization in the pediatric and adolescent athlete. Orthop Clin North Am. 2015;46(2):249-58. doi: 10.1016/j.ocl.2014.11.004. PubMed PMID: 25771319.
(8) Gallahue DL, Ozmun JC. Understanding Motor Development: Infants, Children, Adolescents, Adults. 6th ed. New York, NY: McGraw-Hill; 2006.
(9) Lai SK, Costigan SA, Morgan PJ, Lubans DR, Stodden DF, Salmon J, Barnett LM. Do school-based interventions focusing on physical activity, fitness, or fundamental movement skill competency produce a sustained impact in these outcomes in children and adolescents? A systematic review of follow-up studies. Sports Med. 2014;44(1):67-79. doi: 10.1007/s40279-013-0099-9. PubMed PMID: 24122775.
(10) Lubans DR, Morgan PJ, Cliff DP, Barnett LM, Okely AD. Fundamental movement skills in children and adolescents: review of associated health benefits. Sports Med. 2010;40(12):1019-35. doi: 10.2165/11536850- 000000000-00000. PubMed PMID: 21058749.
(11) Jurimae T, Jurimae J. Growth, Physical Activity, and Motor Development in Prepubertal Children. Boca Raton, FL: CRC Press LLC; 2000.
(12) Gabbard CP. Lifelong Motor Development. 5th ed. San Francisco, CA: Pearson Benjamin Cummings; 2008.
(13) Fitts PM, Posner MI. Human Performance. Belmont: Brooks/Cole; 1967.
(14) Feijen L, Hodges NJ, Beek PJ. Acquiring a novel coordination skill without practicing the correct motor commands. J Mot Behav. 2010;42:295-306.
(15) Wulf G. Attentional focus and motor learning: a review of 15 years. Int Rev Sport Exerc Psychol. 2013;6:77-104.
(16) Wulf G, Shea C, Lewthwaite R. Motor skill learning and performance: a review of influential factors. Med Educ. 2010;44:75-84.
(17) Bergeron M, Mountjoy M, Armstrong N, Chia M, Côté J, Emery C, Faigenbaum A, Hall G, Kriemler S, Léglise M, Malina R, Pensgaard A, Sanchez A, Soligard T, Sundgot-Borgen J, van Mechelen W, Weissensteiner J, Engebretsen L. International Olympic Committee consensus statement on youth athletic development. BritishJournal of Sports Medicine. 2015;49(13):843-51.
(18) Lloyd R, Oliver J, Faigenbaum A, Howard R, De Ste Croix M, Williams C, Best T, Alvar B, Micheli L, Thomas D, Hatfield D, Cronin J, Myer G. Long-term athletic development-Part 1: A pathway for all youth. Journal of Strength and Conditioning Research. 2015;29(5):1439-50.
(19) Faigenbaum A, Lloyd R, MacDonald J, Myer G. Citius, Altius, Fortius: Beneficial effects of resistance training for young athletes British Journal of Sports Medicine. 2015;epub before print.
(20) Lloyd R, Faigenbaum A, Stone M, Oliver J, Jeffreys I, Moody J, Brewer C, Pierce K, McCambridge T, Howard R, Herrington L, Hainline B, Micheli L, Jaques R, Kraemer W, McBride M, Best T, Chu D, Alvar B, Myer G. Position statement on youth resistance training: the 2014 International Consensus. British Journal of Sports Medicine. 2014;48(7):498-505.
(21) Cohen D, Voss C, Taylor M, Delextrat A, Ogunleye A, Sandercock G. Ten-year secular changes in muscular fitness in English children. Acta Paediatrica. 2011;100(10):e175-e7.
(22) Hardy L, Barnett L, Espinel P, Okely A. Thirteen-year trends in child and adolescent fundamental movement skills: 1997-2010. Medicine and Science in Sports and Exercise. 2013;45(10):1965-70.
(23) Runhaar J, Collard DC, Singh A, Kemper HC, van Mechelen W, Chinapaw M. Motor fitness in DUtch youth: Differences over a 26-year period (1980-2006). Journal of Scinece and Medicine in Sport. 2010;13:323-8.
(24) American Academy of Pediatrics. Baseball and softball. Pediatrics. 2012;129(4):e842-56.
(25) Leek D, Carlson J, Cain K, Henrichon S, Rosenberg D, Patrick K, Sallis JF. Physical activity during youth sports practices. Archives of Pediatric and Adolescent Medicine. 2010;165(4):294-9.
(26) Guagliano J, Rosenkranz R, Kolt G. Girls' physical activity levels during organized sports in Australia. Medicine and Science in Sports and Exercise. 2013;45(1):116-22.
(27) Lauersen J, Bertelsen D, Andersen L. The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. British Journal of Sports Medicine. 2014;48(11):871-7.
(28) Faigenbaum A, Lloyd R, Myer G. Youth resistance training: Past practices, new perspectives and future directions. Pediatric Exercise Science. 2013;25:591-604.
(29) Oliver J, Lloyd J, Meyers R. Training elite child athletes: promoting welfare and wellbeing. Strength and Conditioning. 2011;33(4):73-9.
(30) Difiori J, Benjamin H, Brenner J, Gregory A, Jayanthi N, Landry G, Luke A. Overuse injuries and burnout in youth sports: a position statement from the American medical society for sports medicine. Clinical Journal of Sports Medicine. 2014;24(1):3-20.
(31) Lloyd R, Oliver J, Faigenbaum A, Howard R, De Ste Croix M, Williams C, Best T, Alvar B, Micheli L, Thomas D, Hatfield D, Cronin J, Myer G. Long-term physical development: Barriers to success and potential solutions-Part 2. Journal of Strength and Conditioning Research. 2015;29(5):1451-64.
(32) Behringer M, Vom Heede A, Matthews M, Mester J. Effects of strength training on motor performance skills in children and adolescents: a meta-analysis. Pediatric Exercise Science. 2011;23(2):186-206.
(33) Myer G, Faigenbaum A, Edwards E, Clark. J., Best T, Sallis R. 60 minutes of what? A developing brain perspective for activation children. British Journal of Sports Medicine. 2015;epub before print.
(34) Behringer M, vom Heede A, Yue Z, Mester J. Effects of resistance training in children and adolescents: A metaanalysis. Pediatrics. 2010;126(5):e1199-e210.
(35) Faigenbaum A, Myer G. Resistance training among young athletes: Safety, efficacy and injury prevention effects. British Journal of Sports Medicine. 2010;44:56-63.
(36) Myer G, Faigenbaum A, Chu D, Falkel J, Ford K, Best T, Hewett T. Integrative training for children and adolescents:techniques and practices for reducing sports-related injuries and enhancing athletic performance. Physician andSports Medicine. 2011;39(1):74-84.
(37) Krajnik S, Fogarty KJ, Yard EE, Comstock RD. Shoulder injuries in US high school baseball and softball athletes,
2005-2008. Pediatrics. 2010;125(3):497-501. doi: 10.1542/peds.2009-0961. PubMed PMID: 20142288.
(38) Fleisig GS, Andrews JR, Cutter GR, Weber A, Loftice J, McMichael C, Hassell N, Lyman S. Risk of serious injury for young baseball pitchers: A 10-year prospective study. Am J Sport Med. 2011;39(2):253-7. doi: 10.1177/0363546510384224.
(39) Lyman S, Fleisig GS, Andrews JR, Osinski ED. Effect of pitch type, pitch count, and pitching mechanics on risk of elbow and shoulder pain in youth baseball pitchers. Am J Sports Med. 2002;30(4):463-8. PubMed PMID: 12130397.
(40) Lyman S, Fleisig GS, Waterbor JW, Funkhouser EM, Pulley L, Andrews JR, Osinski ED, Roseman JM. Longitudinal study of elbow and shoulder pain in youth baseball pitchers. Med Sci Sports Exerc. 2001;33(11):1803-10. PubMed PMID: 11689728.
(41) Chambless KM, Knudtson J, Eck JC, Covington LA. Rate of injury in minor league baseball by level of play. American journal of orthopedics. 2000;29(11):869-72. Epub 2000/11/18. PubMed PMID: 11079105.
(42) Conte S, Requa RK, Garrick JG. Disability days in major league baseball. Am J Sports Med. 2001;29(4):431-6. PubMed PMID: 11476381.
(43) McFarland EG, Wasik M. Epidemiology of collegiate baseball injuries. Clin J Sport Med. 1998;8(1):10-3. PubMed PMID: 9448950.
(44) Posner M, Cameron KL, Wolf JM, Belmont PJ, Jr., Owens BD. Epidemiology of Major League Baseball injuries. Am J Sports Med. 2011;39(8):1676-80. doi: 10.1177/0363546511411700. PubMed PMID: 21709023.
(45) Oberlander MA, Chisar MA, Campbell B. Epidemiology of shoulder injuries in throwing and overhead athletes. Sports Med Arthrosc. 2000;8(2):115-23. doi: Doi 10.1097/00132585-200008020-00001. PubMed PMID: WOS:000165896400001.
(46) Fleisig GS, Andrews JR, Dillman CJ, Escamilla RF. Kinetics of baseball pitching with implications about injury mechanisms. Am J Sports Med. 1995;23(2):233-9. PubMed PMID: 7778711.
(47) Oyama S, Yu B, Blackburn JT, Padua DA, Li L, Myers JB. Effect of excessive contralateral trunk tilt on pitching biomechanics and performance in high school baseball pitchers. Am J Sports Med. 2013;41(10):2430-8. doi: 10.1177/0363546513496547. PubMed PMID: 23884305.
(48) Davis JT, Limpisvasti O, Fluhme D, Mohr KJ, Yocum LA, Elattrache NS, Jobe FW. The effect of pitching biomechanics on the upper extremity in youth and adolescent baseball pitchers. Am J Sports Med. 2009;37(8):1484-91. doi: 10.1177/0363546509340226. PubMed PMID: 19633301.
(49) Petty DH, Andrews JR, Fleisig GS, Cain EL. Ulnar collateral ligament reconstruction in high school baseball players: clinical results and injury risk factors. Am J Sports Med. 2004;32(5):1158-64. doi: 10.1177/0363546503262166. PubMed PMID: 15262637.
(50) Fleisig GS, Andrews JR, Cutter GR, Weber A, Loftice J, McMichael C, Hassell N, Lyman S. Risk of serious injury for young baseball pitchers: a 10-year prospective study. Am J Sports Med. 2011;39(2):253-7. doi: 10.1177/0363546510384224. PubMed PMID: 21098816.
(51) Olsen SJ, 2nd, Fleisig GS, Dun S, Loftice J, Andrews JR. Risk factors for shoulder and elbow injuries in adolescent baseball pitchers. Am J Sports Med. 2006;34(6):905-12. doi: 10.1177/0363546505284188. PubMed PMID: 16452269.
(52) Guidelines for Youth and Adolescent Pitchers. Pitch Smart; USA Baseball, 2014.
(53) Major League Baseball and USA Baseball: Pitch Smart 2014 [updated 2014]. Available from: http://m.mlb.com/pitchsmart/.
(54) Little League Online 2011. Available from: http://www.littleleague.org/about/aroundtheworld.asp.
(55) Ebbeck V, Weiss MR. Determinants of children's self-esteem: An examination of perceived competence and affect in sport. Pediatric Exercise Science. 1998;10:285-98.
(56) Schmidt GW, Stein GL. Sport commitment: A model integrating enjoyment, dropout, and burnout. Journal of Sport and Exercise Psychology. 1991;13:254-65.
(57) Raedeke TD. Is athlete burnout more than just stress? A sport commitment perspective. Journal of Sport and Exercise Psychology. 1997;19:396-417.
(58) DeFreese JD, Smith AL, Raedeke TD. Individual and Organizational Solutions to Athlete Burnout. In: Williams JM, Krane V, editors. Applied Sport Psychology. 7 ed. New York: McGraw-Hill; 2015.
(59) Gustafsson H, Kenttä G, Hassmén P. Athlete burnout: an integrated model and future research directions. International Review of Sport and Exercise Psychology. 2011;4(1):3-24. doi: 10.1080/1750984x.2010.541927.
(60) Raedeke TD, Smith AL. Coping resources and athlete burnout: An examination of stress mediated and moderation hypotheses. Journal of Sport and Exercise Psychology. 2004;26:525-41.
(61) DeFreese JD, Smith AL. Teammate social support, burnout, and self-determined motivation in collegiate athletes. Psychology of Sport and Exercise. 2013;14(2):258-65. doi: 10.1016/j.psychsport.2012.10.009.
(62) Amorose AJ, Anderson-Butcher D. Autonomy-supportive coaching and self-determined motivation in high school and college athletes: A test of self-determination theory. Psychology of Sport and Exercise. 2007;8(5):654-70. doi: 10.1016/j.psychsport.2006.11.003.
(63) Hollembeak J, Amorose AJ. Perceived Coaching Behaviors and College Athletes' Intrinsic Motivation: A Test of Self-Determination Theory. Journal of Applied Sport Psychology. 2005;17(1):20-36. doi:10.1080/10413200590907540.
(64) Mageau GA, Vallerand RJ. The coach-athlete relationship: A motivational model. Journal of Sports Sciences. 2003;21:883-904.
(65) Visek AJ, Harris B, Blom LC. Mental Training with Youth Sport Teams: Developmental Considerations and Best Practice Recommendations. J Sport Psychol Action. 2013;4(1). Epub 2013/11/26. doi: 10.1080/21520704.2012.733910. PubMed PMID: 24273682; PMCID: 3834981.
(66) Myer GD, Jayanthi N, Difiori JP, Faigenbaum AD, Kiefer AW, Logerstedt D, Micheli LJ. Sport Specialization, Part I: Does Early Sports Specialization Increase Negative Outcomes and Reduce the Opportunity for Success in Young Athletes? Sports health. 2015;7(5):437-42. Epub 2015/10/27. doi: 10.1177/1941738115598747. PubMed PMID: 26502420; PMCID: 4547120.
(67) Jayanthi N, Pinkham C, Durazo R, Dugas L, Luke A. The risks of sports specialization and rapid growth in young athletes. Clin J Sports Med. 2011;21(2):157.
(68) Jayanthi NA, LaBella CR, Fischer D, Pasulka J, Dugas LR. Sports-specialized intensive training and the risk of injury in young athletes: a clinical case-control study. Am J Sports Med. 2015;43(4):794-801. doi: 10.1177/0363546514567298. PubMed PMID: 25646361.
(69) Côté J, Fraser-Thomas J. Youth involvement in sport. In: Crocker P, editor. Sport psychology: A Canadian perspective. Toronto: Pearson; 2007. p. 270-98.
(70) Côté J, Baker J, Abernethy B. Practice and play in the development of sport expertise. In: Tenebaum G, Ecklund RC, editors. Handbook of sport psychology. 3rd ed. Hoboken: Wiley; 2007. p. 184-202.
(71) Brenner JS, American Academy of Pediatrics Council on Sports M, Fitness. Overuse injuries, overtraining, and burnout in child and adolescent athletes. Pediatrics. 2007;119(6):1242-5. doi: 10.1542/peds.2007-0887. PubMed PMID: 17545398.
(72) DiFiori JP, Benjamin HJ, Brenner JS, Gregory A, Jayanthi N, Landry GL, Luke A. Overuse injuries and burnout in youth sports: a position statement from the American Medical Society for Sports Medicine. Br J Sports Med. 2014;48(4):287-8. doi: 10.1136/bjsports-2013-093299. PubMed PMID: 24463910.
(73) Gould D, Udry E, Tuffey S, Loehr J. Burnout in competitive junior tennis players: pt 1 - A quantitative psychological assessment. Sport Psychol. 1996;10:322-40.
(74) Jayanthi N, Pinkham C, Dugas L, Patrick B, Labella C. Sports specialization in young athletes: evidence-based recommendations. Sports Health. 2013;5(3):251-7. doi: 10.1177/1941738112464626. PubMed PMID: 24427397; PMCID: 3658407.
(75) Nyland J. Coming to terms with early sports specialization and athletic injuries. J Orthop Sports Phys Ther. 2014;44(6):389-90. doi: 10.2519/jospt.2014.0109. PubMed PMID: 24881902.
(76) Valovich McLeod TC, Decoster LC, Loud KJ, Micheli LJ, Parker JT, Sandrey MA, White C. National Athletic Trainers' Association position statement: prevention of pediatric overuse injuries. J Athl Train. 2011;46(2):206-20. doi: 10.4085/1062-6050-46.2.206. PubMed PMID: 21391806; PMCID: PMC3070508.
(77) DiFiori JP. Evaluation of overuse injuries in children and adolescents. Curr Sports Med Rep. 2010;9(6):372-8. doi: 10.1249/JSR.0b013e3181fdba58. PubMed PMID: 21068572.
(78) Launay F. Sports-related overuse injuries in children. Orthop Traumatol Surg Res. 2015;101(1 Suppl):S139-47. doi: 10.1016/j.otsr.2014.06.030. PubMed PMID: 25555804.
(79) Paterno MV, Taylor-Haas JA, Myer GD, Hewett TE. Prevention of overuse sports injuries in the young athlete. Orthop Clin North Am. 2013;44(4):553-64. doi: 10.1016/j.ocl.2013.06.009. PubMed PMID: 24095071; PMCID: PMC3796354.
(80) Barynina I, Vaitsekhovskii S. The aftermath of early sports specialization for highly qualified swimmers. Fitness Sports Rev Int. 1992;27:132-3.
(81) Capranica L, Millard-Stafford ML. Youth sport specialization: how to manage competition and training? International journal of sports physiology and performance. 2011;6(4):572-9. PubMed PMID: 22174125.
(82) Feeley BT, Agel J, LaPrade RF. When Is It Too Early for Single Sport Specialization? Am J Sports Med. 2015. doi: 10.1177/0363546515576899. PubMed PMID: 25825379.
(83) Wiersma L. Risks and benefits of youth sport specialization: perspectives and recommendations. Pediatr Exerc Sci. 2000;12:13-22.
(84) Wojtys EM. Sports Specialization vs Diversification. Sports Health. 2013;5(3):212-3. doi: 10.1177/1941738113484130. PubMed PMID: 23734282; PMCID: PMC3658411.
(85) Wall M, Côté J. Developmental activities that lead to dropout and investment in sport. Phys Educ Sport Pedagogy. 2007;12:77-87.
(86) Baker J, Côté J, Abernethy B. Learning from the experts: practice activities of expert decision makers in sport. Res Q Exerc Sport. 2003;74(3):342-7. doi: 10.1080/02701367.2003.10609101. PubMed PMID: 14510301.
(87) Moesch K, Elbe AM, Hauge ML, Wikman JM. Late specialization: the key to success in centimeters, grams, or seconds (cgs) sports. Scand J Med Sci Sports. 2011;21(6):e282-90. doi: 10.1111/j.1600-0838.2010.01280.x. PubMed PMID: 21401722.
(88) Robertson-Wilson J, Baker J, Derbinshyer E, Côté J. hildhood sport involvement in active and inactive adult females. AVANTE. 2003;9:1-8.
(89) Côté J, Lidor R, Hackfort D. ISSP position stand: To sample or to specialize? Seven postulates about youth sport activiites that lead to continued participation and elite performance. USEP. 2009;9:7-17.
(90) Sports and Fitness Industry Association (2019). Sports, Fitness, and Leisure Activities Topline Participation Report. Retrieved from https://www.sfia.org/
(91) Common Baseball Injuries. (n.d.) Retrieved from http://web.usabaseball.com/arc/health-and-safety/generalhealth/common-baseball-injuries/