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Original articles  SPORT INJURIES AND REHABILITATION 

The Journal of Sports Medicine and Physical Fitness 2003 December;43(4):493-9

Copyright © 2009 EDIZIONI MINERVA MEDICA

language: English

Magnetic resonance imaging of the rotator cuff muscles after baseball pitching

Yanagisawa O. 1, Niitsu M. 2, Takahashi H. 3, Itai Y. 2

1 Doctoral Program in Medical Science, Japan University of Tsukoba, Tsukuba, Japan 2 Department of Radiology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan 3 Japan Institute of Sports Sciences, Tokyo, Japan


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Aim. The pur­poses of ­present ­study ­were to inves­ti­gate quan­ti­ta­tively ­using func­tional MR ­imaging the ­effect of a ­series of ­throwing activ­ities on ­rotator ­cuff mus­cles and to com­pare the ­effect of ­pitching ­with ­that of all-out ­shoulder ­external ­rotator exer­cise as the tar­geted ­external ­rotator ­muscle ­group (the infra­spin­atus and the ­teres ­minor).
­Methods. Experi­mental ­design: MRI meas­ure­ments ­after 135 base­ball ­pitches or all-out ­shoulder ­external ­rotator exer­cise (con­cen­tric ­mode) in ­each ­subject’s non­dom­i­nant ­shoulder. Par­tic­i­pants: 6 ama­teur base­ball ­pitchers. Meas­ures: ­serial T2-­weighted ­images of ­rotator ­cuff mus­cles ­were ­obtained ­before ­pitching (or ­shoulder exer­cise) and imme­di­ately, 30, 60 min, 24, 48, 96 hrs ­after ­pitching (or ­shoulder exer­cise). T2 relax­a­tion ­times (T2) at ­each meas­ure­ment ­time ­were cal­cu­lated for the ­rotator ­cuff mus­cles.
­Results. ­Both the supras­pin­atus and the ­external ­rotator ­muscle ­group ­showed sig­nif­i­cant T2 ele­va­tions ­until 96 hrs ­after ­pitching. The sub­sca­pu­laris ­also ­showed sig­nif­i­cantly ­increased T2 ­until post­pitching 48 hrs. On the ­other ­hand, a sig­nif­i­cant T2 ele­va­tion con­tinued ­until 60 min ­after ­shoulder exer­cise, but there­after ­returned ­towards the ­value at ­rest ­over the ­next 24 hrs.
Con­clu­sion. ­Long ­lasting T2 ele­va­tions in ­rotator ­cuff mus­cles ­would be asso­ciated ­with an ­increase in ­each intra­mus­cular ­water con­tent, and may be attrib­uted to the ­muscle ­damage ­that ­resulted ­from eccen­tric con­trac­tion ­during ­pitching. ­This infor­ma­tion ­should ­serve as a ­useful com­ple­ment to ­shoulder ­injury pre­ven­tion for base­ball ­pitchers.

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