Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/44368
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Type: Journal article
Title: Relative contributions of infraspinatus and deltoid during external rotation in healthy shoulders
Author: Bitter, N.
Clisby, E.
Jones, M.
Magarey, M.
Jaberzadeh, S.
Sandow, M.
Citation: Journal of Shoulder and Elbow Surgery, 2007; 16(5):563-568
Publisher: Mosby Inc
Issue Date: 2007
ISSN: 1058-2746
1532-6500
Statement of
Responsibility: 
Natalie L. Bitter, Elizabeth F. Clisby, Mark A. Jones, Mary E. Magarey, Shapour Jaberzadeh and Michael J. Sandow
Abstract: Balanced forces around the shoulder are important for normal function; however, rehabilitation guidelines are not well defined because the muscle contributions and optimal exercise technique to recruit them are poorly understood. This study aimed to determine (1) the conditions of resisted isometric external rotation that optimized the contribution of infraspinatus and (2) the load of external rotation at which the adduction strategy was most effective at reducing deltoid contributions. Eighteen subjects with healthy shoulders (n = 36) performed resisted isometric external rotation at 3 increasing loads--10%, 40%, and 70% of their maximal resisted external rotation voluntary isometric contraction--with and without adduction. Surface electromyographic activity of the infraspinatus, posterior and middle deltoid, and pectoralis major was recorded and normalized against the average activity of all 4 muscles, representing each muscle's relative contribution to the task. To optimize the relative contribution of the infraspinatus with the least deltoid involvement during isometric external rotation, a load between 10% and 40% maximal voluntary isometric contraction is appropriate. At low loads, use of the adduction strategy during external rotation reduces middle deltoid involvement. In contrast, the posterior deltoid is activated in parallel with the infraspinatus at low loads and may even act as an adductor with the arm by the side. This study provides a useful guide to optimize rehabilitative exercises for rotator cuff dysfunction; in particular, highlighting that activation of the deltoid could be counterproductive to infraspinatus retraining.
Keywords: Muscle, Skeletal
Shoulder Joint
Humans
Electromyography
Range of Motion, Articular
Sensitivity and Specificity
Pilot Projects
Sampling Studies
Isometric Contraction
Rotation
Reference Values
Adult
Middle Aged
Female
Male
Description: Copyright © 2007 Journal of Shoulder and Elbow Surgery Board of Trustees Published by Mosby, Inc.
DOI: 10.1016/j.jse.2006.11.007
Description (link): http://www.elsevier.com/wps/find/journaldescription.cws_home/623149/description#description
Appears in Collections:Aurora harvest
Orthopaedics and Trauma publications

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