An Acute Throwing Episode Decreases Shoulder Internal Rotation

Kibler WB, Sciascia A, Moore S.  Clin Orthop Relat Res. 2011 Dec 17. [Epub ahead of print]

Glenohumeral range of motion has been examined for decades in baseball players.  It is comprised of both glenohumeral internal rotation (GIR) and glenohumeral external rotation (GER).  In addition, the sum of the GIR and GER has been termed total arc of motion (TAM).  It has been suggested that decreases in GIR and TAM and increases in GER are associated with shoulder and elbow injuries.  However, the temporal response of an acute bout of throwing on shoulder motion is currently not known.  Therefore the objectives of this study were to determine if (1) GIR and TAM would change in response to a 4-day pitching cycle; (2) the change in GIR would be slow to return to baseline; and (3) rotation magnitude and duration would differ between starters and relievers. They measured GIR, GER, and TAM in 45 professional baseball pitchers (starters = 22 and relievers = 23) before a live game pitching outing (averaged 61 pitches for starters and 41 for relievers), immediately after, 24, 48, and 72 hours after throwing.  The team did not perform any stretching, ice, exercise or massage after throwing.  They only perform aerobic exercise.  Shoulder measures were performed using standard goniometer measurements with the scapula stabilized.  They found that GIR was significantly greater prior to throwing compared to all of the post throwing time points (immediately following, 24, 48, and 72 hours).  They also found that GER increased following throwing and remained elevated until 72 hours post throwing when it returned to baseline.  Therefore, TAM remained the same until 72 hours post throwing when it decreased. 

When it comes to throwing there are both acute and chronic effects.  They both have separate etiologies but help us to understand the overall adaptations that occur to the throwing shoulder. To date research hasn’t performed many studies to separate the two.  This was a nice examination of the isolated acute effects of throwing and to identify what clinicians can expect to see following pitching.  They found that the main motion effected following throwing is GIR and doesn’t return to baseline at the 72 hour time point.  GER is also effected but does return to baseline by 72 hours.  These findings suggest to me that since GIR does not return to baseline prior to 72 hours (the normal off time after a pitching session) then pitchers need to augment with stretching to regain that motion.  GIR has been linked to shoulder and elbow injuries so it is important to regain this motion.  If motion is not restored prior to another bout of throwing the reductions in GIR may be exasperated and continue to worsen.  This main be one of the mechanisms that cause the development of glenohumeral internal rotation deficits (GIRD).  The other interesting finding is that GER increased and remained increased until 72 hours post throwing.  When calculating TAM these findings of decreased GIR and increased GER cause TAM to remain unchanged and would suggest that everything is normal.  This stresses the importance of examining the measures separately, in addition to the sum, to identify which motion is being affected.   I hope this is only the start of research examining these acute and semi-chronic effects of throwing.  There are still many unanswered questions including if players do continue throwing without returning GIR to baseline does their baseline measures progressively worsen throughout the season?  Is this change in motion initially from muscular stiffness and progress to capsular adaptations in a more chronic state?  These are all questions that need to be answered.

Written by:  Stephen Thomas
Reviewed by:  Jeffrey Driban

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Kibler WB, Sciascia A, & Moore S (2011). An Acute Throwing Episode Decreases Shoulder Internal Rotation. Clinical Orthopaedics and Related Research PMID: 22179981