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      Does a SLAP lesion affect shoulder muscle recruitment as measured by EMG activity during a rugby tackle?

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      1 , , 2 , 1
      Journal of Orthopaedic Surgery and Research
      BioMed Central

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          Abstract

          Background

          The study objective was to assess the influence of a SLAP lesion on onset of EMG activity in shoulder muscles during a front on rugby football tackle within professional rugby players.

          Methods

          Mixed cross-sectional study evaluating between and within group differences in EMG onset times. Testing was carried out within the physiotherapy department of a university sports medicine clinic. The test group consisted of 7 players with clinically diagnosed SLAP lesions, later verified on arthroscopy. The reference group consisted of 15 uninjured and full time professional rugby players from within the same playing squad. Controlled tackles were performed against a tackle dummy. Onset of EMG activity was assessed from surface EMG of Pectorialis Major, Biceps Brachii, Latissimus Dorsi, Serratus Anterior and Infraspinatus muscles relative to time of impact. Analysis of differences in activation timing between muscles and limbs (injured versus non-injured side and non injured side versus matched reference group).

          Results

          Serratus Anterior was activated prior to all other muscles in all (P = 0.001-0.03) subjects. In the SLAP injured shoulder Biceps was activated later than in the non-injured side. Onset times of all muscles of the non-injured shoulder in the injured player were consistently earlier compared with the reference group. Whereas, within the injured shoulder, all muscle activation timings were later than in the reference group.

          Conclusions

          This study shows that in shoulders with a SLAP lesion there is a trend towards delay in activation time of Biceps and other muscles with the exception of an associated earlier onset of activation of Serratus anterior, possibly due to a coping strategy to protect glenohumeral stability and thoraco-scapular stability. This trend was not statistically significant in all cases

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          Most cited references51

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          Kinetics of baseball pitching with implications about injury mechanisms.

          Elbow and shoulder kinetics for 26 highly skilled, healthy adult pitchers were calculated using high-speed motion analysis. Two critical instants were 1) shortly before the arm reached maximum external rotation, when 67 N-m of shoulder internal rotation torque and 64 N-m of elbow varus torque were generated, and 2) shortly after ball release, when 1090 N of shoulder compressive force was produced. Inability to generate sufficient elbow varus torque may result in medial tension, lateral compression, or posteromedial impingement injury. At the glenohumeral joint, compressive force, joint laxity, and 380 N of anterior force during arm cocking can lead to anterior glenoid labral tear. Rapid internal rotation in combination with these forces can produce a grinding injury factor on the labrum. After ball release, 400 N of posterior force, 1090 N of compressive force, and 97 N-m of horizontal abduction torque are generated at the shoulder; contribution of rotator cuff muscles in generating these loads may result in cuff tensile failure. Horizontal adduction, internal rotation, and superior translation of the abducted humerus may cause subacromial impingement. Tension in the biceps tendon, due to muscle contraction for both elbow flexion torque and shoulder compressive force, may tear the anterosuperior labrum.
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            SLAP lesions of the shoulder.

            A specific pattern of injury to the superior labrum of the shoulder was identified arthroscopically in twenty-seven patients included in a retrospective review of more than 700 shoulder arthroscopies performed at our institution. The injury of the superior labrum begins posteriorly and extends anteriorly, stopping before or at the mid-glenoid notch and including the "anchor" of the biceps tendon to the labrum. We have labeled this injury a "SLAP lesion" (Superior Labrum Anterior and Posterior). There were 23 males and four females with an average age of 37.5 years. Time from injury to surgery averaged 29.3 months. The most common mechanism of injury was a compression force to the shoulder, usually as the result of a fall onto an outstretched arm, with the shoulder positioned in abduction and slight forward flexion at the time of the impact. The most common clinical complaints were pain, greater with overhead activity, and a painful "catching" or "popping" in the shoulder. No imaging test accurately defined the superior labral pathology preoperatively. We divided the superior labrum pathology into four distinct types. Treatment was performed arthroscopically based on the type of SLAP lesion noted at the time of surgery. The SLAP lesion, which has not been previously described, can be diagnosed only arthroscopically and may be treated successfully by arthroscopic techniques alone in many patients.
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              Is there a role for transversus abdominis in lumbo-pelvic stability?

              P Hodges (1999)
              There has been considerable interest in the literature regarding the function of transversus abdominis, the deepest of the abdominal muscles, and the clinical approach to training this muscle. With the development of techniques for the investigation of this muscle involving the insertion of fine-wire electromyographic electrodes under the guidance of ultrasound imaging it has been possible to test the hypotheses related to its normal function and function in people with low back pain. The purpose of this review is to provide an appraisal of the current evidence for the role of transversus abdominis in spinal stability, to develop a model of how the contribution of this muscle differs from the other abdominal muscles and to interpret these findings in terms of the consequences of changes in this function.
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                Author and article information

                Journal
                J Orthop Surg Res
                Journal of Orthopaedic Surgery and Research
                BioMed Central
                1749-799X
                2010
                25 February 2010
                : 5
                : 12
                Affiliations
                [1 ]Sheffield Centre for Sports Medicine, University of Sheffield, UK
                [2 ]Centre of Rehabilitation and Human Performance Research, University of Salford, UK
                Article
                1749-799X-5-12
                10.1186/1749-799X-5-12
                2842247
                20184752
                f89fb8d7-5bb4-4cf8-9084-61699188833b
                Copyright ©2010 Horsley et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 12 January 2008
                : 25 February 2010
                Categories
                Research article

                Surgery
                Surgery

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