Youth baseball participation from ages 6 – 12 years of age account for over 4 million athletes.  While participation rates fluctuate slightly there is cause for concern regarding the increased incidence of reported arm pain during a regular season specifically at the shoulder and elbow.  Factors associated with incidence of shoulder and elbow pain include improper pitching mechanics, year round play, showcase participation at tryouts, playing on multiple teams, inadequate recovery between pitching outings and overtraining or training errors. 

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The repetitive pitching motion in youth baseball places extraordinary stress on the immature musculoskeletal system.  A complete understanding of these stress forces and the relationship to pitch mechanics is crucial for coaches, parents, athletes and sports medicine clinicians to reduce the incidence of injury and maintain maximum performance.  The pitching motion can be thought of as the coordinated interaction of body segments stacked upon each other in a sequential pattern from the ground up.  There is a common belief among sports medicine clinicians that proper pitching mechanics, taught early, may help reduce the risk of injury by minimizing the detrimental forces placed on the segments of the kinetic chain from the foot to the hand as they interact.

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There are generally six phases of pitching accepted by coaches that include the wind‐up, stride (early cocking), late cocking, acceleration, deceleration, and follow through.  The lower extremity, pelvis and trunk are responsible for initiating the wind-up phase of the pitching motion with the production of kinetic force and a stable base from which to generate movement down the mound.  This energy cascades through the phase of pitching picking up speed as it reaches the shoulder and elbow which in turn imparts this force on the baseball as velocity.  The stride phase in baseball pitching is initiated after the lead side knee reaches its maximum height and the player’s starts movement towards home plate.  The stride phase encompasses movement patterns including arm path, foot placement and contact stride angle, stride length, arm position at foot contact and the relationship of speed and timing between the lead leg hips and dominant shoulder segment. Late cocking incorporates elbow position in flexion, shoulder external rotation and trunk inclination forward angle. It has been reported that pitchers who have experienced shoulder injuries often indicate that the late cocking phase of pitching, specifically in the position where maximum shoulder external rotation (MER) occurs.  The MER position is reported to be between 166 and 178 degrees at the transition from late cocking to acceleration phase of pitching. Elbow flexion position is reported to be 74-85 degrees at foot contact during the stride phase while knee flexion is between 40-49 degrees. Thomson SF, et al reported that in younger pitchers the most common uniform characteristics in healthy youth was the position of the elbow, specifically flexion, at foot contact, the total amount or maximum elbow flexion, and MER as described above. The position of the elbow at foot contact during the stride phase is recognized as an important parameter for pitching efficiency. The 90 degree flexion position with the elbow at shoulder height during this segment of the phase is thought to be ideal by many coaches. 

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The goal then is to correct inefficient pitching mechanics that can contribute to high valgus loads at the elbow to assist coaches in training techniques. The acceleration phase includes dominant arm shoulder internal rotation velocity, trunk forward flexion and side bending movements towards the target, and body position at ball release. The deceleration and follow through phase includes trunk positioning, lead leg extension, and the subsequent dissipation of force through upper extremity horizontal adduction and trunk forward flexion. 

Utilizing high speed video analysis can enabled an accurate dissection and description of these sub‐segments of the major phases of pitching.  The analysis can give valuable information on training techniques, form efficiency and developing specific neuromuscular patterns in the design of prevention of injury strategies. 

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It is important to train form and technique at a young age so that the sequential acceleration and deceleration of body segments can transfer the energy needed to throw a baseball effectively and efficiently.  Whether training for improved performance or returning from a throwing injury it is important to include a systematic and comprehensive strategy to incorporate all segments of the motion.  The pre-throwing activities should include proper functional warm-up, and progressive throwing prior to pitching from a regulation indoor mound.  Shadow pitching is described as using an implement, often a towel drill, rather than a ball to perform the throwing motion in preparation for actual pitching. Shadow pitching acts to neurologically pre-program the muscles and tendons so that repeated consistent form can be achieved during practice and competition.  Recent research has questioned whether shadow pitching (towel drill) can have an adverse effect on the pitching motion by changing the muscle recruitment patterns and thus negatively affecting throwing form specifically at the ball release (BR) phase and increasing shoulder joint forces.  The driving question is does shadow pitching using the towel drill mirror the actual throwing motion when utilizing the ball or does it change mechanics?

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The pilot investigation purpose was to compare the pitching motion utilizing shadow pitching technique with the towel drill, Strikeout Strippz (Perfect Throw USA) and compare that to a regulation baseball thrown by the same pitcher.  Players between the ages of 13 – 20 were included in the pilot data collection to determine age related differences in the throwing motion from a single baseball training facility with parental consent.  Each pitcher was instructed in the proper fit and performance related information for the Strikeout Strippz and towel, while each was instructed on the standard grip for a four seam fast ball for the live pitching testing.  Video analysis was performed for sagittal (side-view) and frontal view positions utilizing Dartfish software (Dartfish USA, Inc.) that was digitalized for motion measurements by a single clinician to measure stride length, elbow flexion at foot flat, shoulder abduction, and lead side knee flexion at foot flat.  Additionally 4 pitchers (14-22 years of age) were tested utilizing high speed motion capture to compare throwing shoulder horizontal abduction, elevation and external and internal rotation, elbow flexion at ball release, and lateral trunk flexion at ball release. 

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The dartfish acquired sagittal (Side-view) key results indicate that the elbow flexion angle at foot flat becomes more acute with greater flexion (24 deg) when using a towel drill as compared to ball thus positioning the hand closer to the head with greater than 90 degrees of elbow flexion.  The elbow flexion angle at foot flat becomes more acute with less flexion (14 deg) when using the Strikeout Strippz compared to the ball or towel drill thus closer to the 90 degree position. The Strikeout Strippz produced less elbow flexion than the towel which can be described as closer to 90 degrees of elbow flexion many coaches desire.  Following a three week training period the elbow angle at foot flat when using the strap remained consistent (~15 deg) and did not adversely affect a change in pitching form and demonstrated consistency of position.  The stride length change was negligible within training sessions regardless if the athlete was using the towel, Strikeout Strippz, or ball, therefore no device or ball affected stride length. 

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The dartfish acquired frontal view key result demonstrated that the Strikeout Strippz positions the elbow angle 28deg more acute (closer to 90 degrees of elbow flexion) at ball release in collegiate pitchers off the mound when compared to throwing a regulation ball. 

The high speed analysis key results indicated that collegiate pitchers demonstrated increased horizontal shoulder abduction utilizing the Strikeout Strippz with instruction compared to a baseball only (Figure 1) with no significant change utilizing device compared to baseball only in the high school pitcher. (Figure 2)

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Key Take-A-Way

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It is well understood that sequential body segment motions during throwing influences pitch efficiency and joint forces or stress on both the shoulder and elbow. The goal then for coaches and clinicians treating the injured player is to utilize methods of training and return to throw techniques that minimize these stresses while positively affecting the mechanics to reduce the high loads placed on the elbow and shoulder. The shadow pitching, or towel drill has been a mainstay for coaches as a means by which to affect the training for pitchers of all ages. The understanding associated with the potentially detrimental changes in mechanics that the towel drill reinforces should cause coaches to reflect on using this technique. The variables associated with the towel size both in length and density, and the muscular contraction effect of the pitcher gripping the towel has the potential for negative effects on reinforcing good mechanics. While the towel drill has been described as a means to increase the players stride length and follow through form the comparison made with other product methods like the Strikeout Strippz demonstrated a more natural elbow and shoulder position compared to throwing a regulation baseball. The pilot testing data demonstrated a trend towards the Strikeout Strippz, rather than a towel for shadow pitching, positioned the elbow closer to the form exhibited using a regulation baseball. The Strikeout Strippz therefore in our sample size more closely resembles throwing a regulation ball when compared to the towel drill. The consistent elbow position utilizing the Strikeout Strippz in the foot contact stride phase aids in a better hands-on-top position during arm separation which has been associated with reduced HIRT (Humeral Internal Rotation Torque) and Elbow Valgus no instruction instruction device+baseball baseball only Load (EVL) which theoretically should put reduced stress on the elbow ligaments and
the throwing shoulder. 

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In summary the collegiate pitchers utilizing the Strikeout Strippz demonstrated improved shoulder horizontal abduction, a longer stride, greater shoulder internal/external rotation, and improved lateral trunk flexion at ball release. The high school pitchers demonstrated improved shoulder elevation at ball release, improved elbow flexion slot angle at ball release, and improved lateral trunk flexion at ball release. The Strikeout Strippz more closely resembles the pitching motion with a regulation baseball when compared with the towel drill. 

The limitations of this preliminary pilot data include the use of two video analysis methods and small sample size in each category.

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References
      1. Crotin RL et al. Altered stride length in response to increasing exertion among baseball pitchers. Medicine Science and Sports Exercise, 2014, 46: 565-571.

      2. Davis JT et al. The effect of pitching biomechanics on the upper extremity in youth and adolescent baseball pitchers. Am J Sports Med, 2009, 37: 1484-1491.

      3. Dillman CJ et al. Biomechanics of pitching with emphasis upon shoulder kinematics. Journal of Orthopedics and Sports Phys Ther, 1993, 18: 402-408.

      4. Oyama S et al. Improper trunk rotation sequence is associated with increased maximal shoulder external rotation angle and shoulder joint force in high school            baseball pitchers. Am J Sports Med, 2014, 42: 2089-2094.

      5. Thompson SF et al. Youth Baseball Pitching Mechanics: A Systematic Review.  Sports Health. 2018,10: 133-140.

      6. Calabrese GJ , Pitching mechanics, revisited. Int J Sports Phys Ther. 2013 Oct;8(5):652-60.