Electromyographic study during isometric exercise of the shoulder in head-out water immersion

Water exercises are used for early rehabilitation programs after shoulder i njury such as rotator cuff tear, yet no literature discusses the muscle act ivity of such rehabilitation programs in water. The purpose of this study w as to analyze the electromyographic activity from 8 volunteers during isome tric exercises in water and on land Nine isometric exercises were studied: with 30 degrees 60 degrees and 90 degrees shoulder flexion and abduction, a nd 3 positions of shoulder rotation at 0 degrees abduction (both maximal in ternal and external rotation and mid-position). Nine parts of 6 muscles wer e studied: the supraspinatus, infraspinatus, subscapularis, 2 parts of the pectoralis major (clavicular and costal), 3 parts of the deltoid (anterior, middle, and posterior), and the latissimus dorsi. The electromyographic si gnals were low-pass filtered, full-wave rectified, and integrated for 5 sec onds. The electromyographic activity was quantified as a percentage of the maximal manual muscle test. The results showed that supraspinatus activity at 90 degrees abduction significantly decreased from 22.3 +/- 15.8 on land to 3.9 +/- 3.3% manual muscle test in water (P < .01). Other muscle activit ies in wafer also decreased remarkably compared with those on land. These r esults provide valuable information for the safety of water exercise for ea rly rehabilitation programs after shoulder injury such as rotator cuff tear .