Throwing Injuries and Prevention Strategies in Youth Baseball

Abstract

The prevalence and severity of baseball-related injuries in the youth athlete population continue to escalate, despite efforts by health care professionals and sports organizations to quell this trend. This article reviews current research that has investigated the risk factors and possible prevention strategies for the most common injuries in young baseball players, including strengthening programs, pitch count guidelines, and throwing analysis.

As participation in youth baseball rises—with more than 200 000 teams in Little League Baseball alone [13]—the number of adolescent elbow and shoulder injuries rises along with it. Factors such as early sport specialization [21,22], year-round scheduling [14], multiple teams, decreased rest days, playing a secondary position [12], and increased volume [10] may influence the elevated risk of upper-extremity injury, particularly in those athletes who pitch as their primary or secondary position. Because these injuries occur in a skeletally immature population, the possibility of long-term pain and disability is of particular concern.

Throwing a baseball at maximum velocity requires the sequencing of numerous body segments, as well as power generation and energy transfer from the ground to the ball. Musculoskeletal impairments and biomechanical inefficiencies coupled with repetitive throwing and fatigue place stress on multiple joints. At highest risk are the shoulder and elbow, due to the torques they undergo in delivering a high-velocity pitch. To prevent injury in young athletes, it is essential to identify impairments that could lead to inefficient mechanics and potential injury. Prevention should include a musculoskeletal and physical examination, biomechanical analysis, and education on pitch counts and rest.

One controversy centers on the use of weight balls in youth training. Although weight-ball throwing programs have been found to result in an increase in pitching velocity [5], they are also associated with an increased rate of injury [25]. In a recent survey, a majority of baseball pitchers perceived an increased risk of injury but also said they would continue to use a weight-ball throwing program due to anticipated performance advantage [7]. A possible solution is using a lighter ball, which has demonstrated an increase in velocity without the risk of injury [9].

The use of breaking pitches (such as curveballs) for young pitchers has been a contentious topic in the sports medicine community. Due to the wrist movement made during the pitching motion, there is a long-held belief that breaking balls create more stress on the shoulder and elbow. However, several recent studies found that the curveball creates less elbow and shoulder stress than the fastball in both adolescent and professional baseball pitchers [19,30].

Although many teams and organizations are attempting to implement pitch counts, young athletes can circumvent these boundaries by playing on multiple teams and showcases. A recent study found that in pitchers younger than 12 years old, elbow pain was associated with more than 50 pitches per outing or more than 200 pitches per week during the season [18]. Another study in young pitchers found that pitching more than 100 innings per year was a risk factor for shoulder and elbow pain [10]. Consistent education for parents, coaches, and athletes is apparently needed.

Common Throwing Injuries

Injuries in the skeletally immature athlete can differ from those in the mature athlete, especially in the overhead thrower. Lack of strength, especially proximally, as well as open physes in the throwing arm are potential issues for the demands of repetitive throwing. Shoulder and elbow injuries that occur frequently in the skeletally immature throwing athlete are little league shoulder, little league elbow, and osteochondritis dissecans.

Little league shoulder is medically known as proximal humeral epiphysiolysis. In immature throwers with open growth plates, the physis rather than the musculature and ligaments absorbs most of the rotational and distraction forces of throwing. The repetitive stress placed on the physis can lead to a Salter-Harris I fracture, which separates through the physis [6], as well as widening of the physis that can be seen on radiographic images. These injuries may be a threat until full skeletal maturity at ages 18 to 21 years. Symptoms of little league shoulder may include progressive onset of shoulder pain, often laterally during the cocking and acceleration phase of throwing or in active range of motion, and a decrease in velocity and control. In more severe cases, pain at rest may persist. Examination often reveals tenderness to palpation on the lateral proximal humerus at the growth plate, decreased shoulder range of motion, and muscle weakness. Treatment typically involves discontinuing throwing for at least 12 weeks, with core and scapular muscle strengthening followed by 2 to 4 weeks of upper-extremity plyometrics before starting a rehabilitative throwing program.

Little league elbow is medically known as medial epicondyle apophysitis. The repetitive valgus stress on the elbow during the late cocking phase of throwing creates tensile forces between the medial epicondyle and ulnar collateral ligament (UCL). If the apophysis is still open, it will take up more stress than the soft tissue around it (such as the UCL). In severe cases, the medial epicondyle may avulse from the bone as well. The medial epicondyle is the last growth center in the elbow to close, which may occur between ages 10 and 17 years [24]. The athlete may report pain on the medial epicondyle with palpation or throwing, most often during the cocking phase, as well as decreased throwing velocity and control and reduced elbow extension. Treatment involves stopping throwing for at least 12 weeks while completing therapeutic exercises to strengthen muscle and address forearm flexor tightness.

Most elbow injuries in the throwing athlete occur in the medial elbow, but the lateral elbow is also subject to injury, due to repetitive compressive forces that generate large varus stresses at the radiocapitellar joint during the cocking/acceleration phases. This repetitive injury can lead to traumatic degeneration of the subchondral bone, which may be exacerbated by the lack of blood supply to the capitellum [1] and cause capitellum fragmentation and loose body formation. Symptoms of an elbow osteochondritis dissecan lesion include tenderness to palpation of the radiocapitellar joint, swelling, and loss of extension, as well as locking or catching in the elbow, especially if a loose body is present. Treatment depends on the severity of the lesion and if it is stable or unstable. Unstable lesions with loose body formation typically require surgical intervention, such as excision with microfracture or osteochondral autologous transplantation (OATS) with chondral plugs taken from knee cartilage. Stable lesions are often treated nonoperatively with a hinged brace, anti-inflammatories, proximal strengthening, and a break from throwing until symptoms resolve.

Current Injury and Prevention Strategies

The observed increase in upper-extremity injuries in youth baseball suggests these athletes need an arm-care program consisting of strengthening and joint mobility. One study found that total shoulder rotational motion, hip internal rotation range of motion, and thoracic kyphosis angle were the primary modifiable risk factors for medial elbow injury [27]. A randomized controlled trial found that a 10-minute warmup program consisting of 5 stretching, 2 dynamic mobility, and 2 balance training exercises reduced injuries in young players by 50% compared with a control group [28]. The Youth Thrower’s Ten—a variation of the original Thrower’s Ten exercise program developed by Wilk et al [33]—addresses the entire kinetic chain through a multiphasic approach.

One of the most effective, albeit difficult to implement, injury risk-reduction strategies is to limit overall volume of pitches and increase rest [3]. USA Baseball and Major League Baseball have combined to make recommendations that include age considerations and rest days along with an overall year limitation [32] (Table 1). Bohne et al [4] found that young athletes require more education on these guidelines and on injury risk factors.

Table 1.

Pitch count limits and required rest recommendations [16].

Age	Daily max (pitches)	Required rest
		0 Days	1 Day	2 Days	3 Days	4 Days	5 Days
7-8	50	1-20	21-35	36-50	N/A	N/A	N/A
9-10	75	1-20	21-35	36-50	51-65	66+	N/A
11-12	85	1-20	21-35	36-50	51-65	66+	N/A
13-14	95	1-20	21-35	36-50	51-65	66+	N/A
15-16	95	1-30	31-45	46-60	61-75	76+	N/A
17-18	105	1-30	31-45	46-60	61-80	81+	N/A
19-22	120	1-30	31-45	46-60	61-80	81-105	106+

Other studies have shown that there is a significant association between the number of pitches thrown in a game and during the season and elbow and shoulder pain [15]. The importance of rest and recovery is sometimes understated, but young players need time to recover from the microtrauma caused by throwing. Following the recommended rest guidelines proposed by USA Baseball is a good start, but players also need to manage their workload, even at a young age. To minimize risk, other studies have emphasized the importance of adding rest days and monitoring workload in single-sport–specialized youth athletes [20].

Comprehensive injury risk reduction must go beyond the arm-care program and address the entire kinetic chain. Programs that address full-body range of motion and strength address multiple risk factors or impairments [17] and are considered a safe and effective injury risk-reduction strategy for young athletes [29].

Guidelines for Youth Baseball Practice, Competition, and Pitching

The 2022 Sports & Fitness Industry Association’s Topline Participation Report identified more than 5 million athletes between the ages of 6 to 17 years participating in baseball in 2021 [2]. USA Baseball and Major League Baseball have established advisory committees consisting of medical practitioners, sports biomechanists, coaches, and strength and conditioning professionals to develop the American Development Model (ADM) and Pitch Smart to increase sport participation, optimize performance, and minimize the risk of arm injuries in youth baseball [32], including age-appropriate days per week and months per year spent in competition (Table 2) [16].

Table 2.

American development model recreational and advanced track [32].

Recreational track
ADM stage	Age	Training	Competition	Days per week in season	Months of calendar year
Activate	Entry to 7	75%	25%	1-2	4 months
Discover	7 to 12	75%	25%	1-2	4 months
Progress	12 to 14	65%	35%	2-3	4 to 8 months
Develop	14 to 16	65%	35%	3-4	4 to 8 months
Apply	16 to 18	65%	35%	4-5	4 to 8 months
Inspire	ANY	70%	30%	At leisure (>3x per week for health benefits)	Include participation as part of year-round health regiment
Advanced track
ADM stage	Age	Training	Competition	Days per week in season	Months of calendar year
Develop	14 to 16	50%	50%
Apply	16 to 18	45%	55%
Excel	19 +	College/Pro level dependent	College/Pro level dependent	College/Pro level dependent	College/Pro level dependent

The ADM is a developmental pathway to facilitate lifelong participation in baseball. Its 7-stage framework provides athletes, coaches, parents, and leagues guidance for age-specific training goals, proper competition guidelines, and recovery strategies. Each of the 7 stages comprises 6 areas of focus: physical literacy, physical development, injury prevention, psychosocial well-being, specialization, periodization, and competition.

Directed toward players, coaches, and parents, the Pitch Smart guidelines continue to be adopted as youth and amateur baseball organizations become members of the Pitch Smart Compliance Program. Awareness of the Pitch Smart guidelines is still lacking among parents and coaches as reported by Reintgen et al [26].

Throwing Evaluation

To prevent injury and optimize performance, HSS has created an overhead athlete screening that includes musculoskeletal assessment of range of motion, strength, and movement profiling. Assessment begins with cervical, thoracic, and lumbar mobility and progresses to measurements for shoulder flexion, horizontal adduction, and total arc of motion. Elbow flexion and extension, total hip rotation, and ankle dorsiflexion are also evaluated. Gross asymmetries are identified, but well-recognized abnormalities are accepted. For example, as youth athletes age, increases in external rotation on the throwing arm and decreases in internal rotation are expected. However, normal total arcs of motion as described by Wilk et al [34] should be maintained.

Next is a comprehensive strength and balance assessment. The player demonstrates their ability to balance on 1 foot, followed by an assessment of hip, core, shoulder, and forearm strength. Players with UCL tears typically score lower on the Y Balance Test for both the stance and lead lower extremity than non-injured players [11]. Strength is assessed using handheld dynamometers. Ideally, dominant-arm strength is greater than that of the non-dominant arm. Adolescent pitchers with throwing-related pain exhibit reduced dominant-arm strength in the middle trapezius and supraspinatus [31]. Assessment of shoulder endurance is performed using the posterior shoulder endurance test [23].

Weaknesses throughout the kinetic chain that alter the transfer of power can place additional stress on the arm during throwing. A biomechanical assessment evaluating the overhead throw can help identify faulty movement patterns that might increase stress and injury. The player is instructed to throw at maximum velocity off of a mound into a target at the distance used during play. Markerless motion capture studies over 18 joint angles and key metrics including stride length, knee extension, shoulder external rotation, trunk rotation, shoulder abduction, elbow flexion, and hip and shoulder separation. In 2009, Davis et al [8] studied biomechanical parameters that might lower shoulder and elbow torque in 169 youth baseball pitchers; they concluded that proper throwing mechanics (leading with the hips, hand on top of the ball, arm in throwing position, closed shoulder position, and stride foot toward home plate) were correlated with decreased shoulder and elbow torque and improved pitching efficiency.

In conclusion, restrictions on pitch counts combined with physical training can safeguard young baseball throwers. Implementation of these programs requires the efforts of sports medicine professionals, coaches, players, and parents. Identification of important muscle group weakness and altered range of motion throughout the kinetic chain enables early and appropriate corrective measures to be implemented, ultimately reducing the risk of injury in this population.