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Driveline’s Pitching Research Homepage

Shoulder Injury Research

Risk Factors for Shoulder and Elbow Injuries in High School Baseball Pitchers

Authors: Tyler, TF; Mullaney, MJ; Mirabella, MR; Nicholas, SJ; MCHugh, MP

Baseline testing found: athletes dominant arms had less internal rotation (IR), more external rotation (ER) but minimal difference in total range of motion (ROM) in comparison to non-dominant arms.

-This was a study on adolescent (High School) pitchers with relatively low pitching volume whose musculoskeletal systems might not have properly adapted to a pitching motion. There was no conclusive indication that excessive loss of IR or total ROM increased risk of shoulder or elbow injuries. But this does warrant further research of IR and ROM in pitchers of specific populations.

-Preseason supraspinatus weakness (one of four rotator cuff muscles that abducts the shoulder) was related to an increased risk for major injuries (>3 missed games). A training focus should be made of strengthening the supraspinatus (and rotator cuff) in an attempt to prevent injury.

Expand for Vocab
Internal rotation (IR) – term referring to rotation towards the center of the body. If an athlete was laying of their back with their hand at 90 degrees pointing upward, internal rotation would be the motion of the hand going towards the hip.

External rotation (ER) – term referring to rotation away from the body. If an athlete was laying on their back with their hand at 90 degrees pointing upward, external rotation would be the motion of the hand going towards the hip.

Total range of motion (ROM) – Combining internal and external rotation into one measurement

Supraspinatus – one of the four muscles of the rotator cuff muscles. Abducts the arm at the shoulder

Rotator Cuff – group of tendons and muscles in the shoulder that provide stability to the shoulder and connect the upper arm (humerus) to the shoulder blade (scapula)

Preseason Shoulder Strength Measurements in Professional Baseball Pitchers

Authors: Byram, Ian; Bushnell, Brandon; Dugger, Keith; Charron, Kevin; Harrell, Frank; Noonan, Thomas

What we learned from this study:

This study looked at Major and Minor league pitchers from the years 2001-2005. Strength was assessed for prone internal rotation (IR), prone external rotation (PER) seated external rotation (SER) and supraspinatus (one of four rotator cuff muscles that abducts the shoulder).

  • No players were eliminated from the study because of prior injury.
  • There was no control for overuse or type of pitches thrown.
  • There was a significant association between shoulder external rotator and supraspinatus weakness and injury requiring surgery.
    • 70 injuries were found in 50 players, 10 player suffered injuries in multiple seasons
    • 42 injuries were treated nonoperatively, 28 were treated surgically
        • Preseason strength data may help identify players at risk for injury

During throwing motion the glenohumeral joint relies on the rotator cuff and surrounding musculature such as latissimus dorsi and pectoralis major to resist distraction forces. Weakness of the external rotators can lead to a lack of muscular control during lack cocking and deceleration. Therefore strength training plans should be formulated for the rotator cuff as a preventive measure to injury.

Posterior Shoulder Capsules are Thicker and Stiffer in the Throwing Shoulders of Healthy College Baseball Players

Authors: Takenaga, T; Sugimoto, K; Goto, H; Nozaki, M; Fukyoshi, M; Tsuchiya, A; Murase, A; Ono, T; Otsuka, T

It has been reported that the posterior (back) shoulder muscles are thicker in throwing arms than non throwing, which has a relationship to GIRD. This study used Shear-wave ultrasound elastography to measure the stiffness of the thickened capsules.

The posterior capsule, below the infraspinatus, had significantly greater thickness and elasticity (stiffness) in the throwing shoulder vs non throwing. The posteroinferior capsule, below the teres minor, was also significantly thicker and stiffer in the throwing shoulder than non throwing. This suggests that capsular elasticity could more strongly affect GIRD than capsular thickness. More studies are needed with a bigger group size to see if measuring shoulder elasticity in this manner can help identify players at risk.
We want to be able to look at differences in athletes and distinguish common adaptations to repetitive throwing from pathological changes. More progressive studies, like this use, using new non invasive modalities are encouraged.

Relationship between maximum shoulder external rotation angle during throwing and physical variables (Open Access)

Authors: Miyashita, Koji; Urabe, Yukio; Kobayashi, Hirokazu; Yokoe, Kiyoshi; Koshida, Sentaro; Kawamura, Morio; Ida, Kunio

40 high school position players and pitchers participated in a study looking at the relationship between maximum shoulder external rotation (MER) during throwing motions, passive ROM and kinematic variables at stride foot contact (SFC).

MER showed a significant moderate linear correlation with ER and extension angles at SFC in the early cocking phase. It was suggested because of these findings to avoid excessive shoulder IR and extension angles at SFC and to strengthen the internal rotator muscles. There is also a need to maintain passive ROM of ER in a normal range.

Because of the limitations of the study design the researchers were unable to conclude whether the increase of MER was a cause or result of the physical and kinematic variables. More research is needed to find factors contributing to the increase of MER.

Shoulder Adaptations Among Pitchers and Position Players Over the Course of a Competitive Baseball Season

Authors: Laudner, KG; Lynall, R; Meister, K

This study compared 16 pitchers and 16 position players before and after a 140 game season. They were measured in: scapular upward rotation (0,60,90,120 degrees), forward scapular posture. glenohumeral head (GH) range of motion (horizontal adduction, bilateral GH internal rotation ROM). The pitchers in this study completed a team-mandated shoulder exercise program during the season, this was not required of the position players

  • No significant differences in GH horizontal adduction were found
  • No significant differences in  bilateral internal rotation ROM
  • Forward scapular posture and scapular upward rotation at 0 degrees and 120 degrees of humeral elevation were not significantly different
  • Pitchers developed significantly less scapular upward rotation at 60 degrees and 90 degrees of humeral elevation compared to position players

Proposed reasons for this were changes in length tightness and strength of various periscapular muscles such as pectoralis minor, rhomboids, and levator scapulae. Strengthening and stretching of these muscles during the season was suggested.

More studies are needed in comparing ROM of pitchers versus position players over longer time frames such as pre and post season.

Glenohumeral Rotational Range of Motion in Collegiate Overhead-Throwing Athletes During an Athletic Season (Open Access)

Authors: Dwelly, Priscilla; Tripp, Brady; Tripp, Patricia; Eberman, Lindsey; Gorin, Steven

This was an observational study looking at 29 healthy baseball athletes and 19 healthy softball athletes. Measurements were taken over 3 time during one athletic season: prefall, pre spring and post spring. The measures were of glenohumeral ROM: external rotation (ER), internal rotation (IR), total arc and GIRD.

Athletes had increased ER and total arc (because of the ER gains) but their IR did not change significantly over their season.

Both calculations for GIRD (IR difference between dominant and nondominant arms and percentage of total arc) appeared to quantify a specific characteristic of relative ROM, yet they reflected different deficits. More studies are needed to compared the these two measurements of GIRD long term.

Differences in Scapular Upward Rotation between Baseball Pitchers and Position Players

Authors: Laudner, KG; Stanek, JM; Meister K

Baseball pitchers have significantly less scapular upward rotation than do position players at high angles of humeral elevation (60 & 90).

The body will compensate through loss of range of motion in the scapula. Which can impact the function of the kinetic chain and put the shoulder at risk for instability, impingement and further injury

It was suggested that muscle tightness of the rhomboids, levator scapula and pectoralis minor may limit how much upward rotation is available. Because of this we suggest athletes use a lacrosse ball to massage these areas before throwing.

Further studies are needed to investigate the role that joint laxity and muscle fatigue play in the differences of upward rotation of the scapula.

Effects of Acute Static Stretching of the Throwing Shoulder on Pitching Performance of National Collegiate Athletic Association Division III Baseball Players

The researchers had 6 pitchers and 6 position players go through 2 separate throwing protocols, one control group and one group that went through a 6 static stretch routine.The literature on static stretching before exercise has been mixed, usually showing either a decrease or no change in performance.

In the experiment each athlete held the 6 stretches for 30 seconds. The stretches included a horizontal adduction, horizontal abduction, external rotation, internal rotation, flexion and extension stretch.

The 6 stretches did not have any significant effect of pitching performance, velocity or accuracy. This is in line with previous research by Young et al. which proposed that participants with well-developed movements patterns wouldn’t be significantly affected by acute static stretching. This would also somewhat explain why position players experience less accuracy than the pitchers in the study. The pitchers obviously have more experience throwing off a mound.

This study only recorded 10 pitches and there was a rest period of 5-10 minutes before each athlete pitched. This rest may have negated the effects of the static stretching. Results may be different with different time between the stretching and throwing or having the participants throw more pitches.

  • This study was brought to our attention by Jarad Vollkommer

Shoulder Rotator Muscle Dynamometry Characteristics: Side Asymmetry and Correlations with Ball-Throwing Speed in Adolescent Handball Players (Open Access)

This study wanted to compare shoulder external/internal rotator muscle peak and average measurements and then determine the correlations between those measurements and throwing velocity.

The researchers found positive correlations between certain isokinetic measurements and ball speed. The correlation between external rotator muscle peak torques and ball speed was (r=0.69) higher than internal rotator muscle peak torque and ball speed (r=0.61) at the fastest velocity measured(240 degrees/second). This suggests that external rotational force may be more important to higher velocity that internal rotation force. More research is need, especially with baseball players, to examine the relationship between external and internal rotational force and velocity.

There was no significant asymmetry in shoulder external/internal rotator muscle peak torques and average power values at the measured speeds.