Thoracic posture, shoulder muscle activation patterns and isokinetic strength of semi-professional rugby union players
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Date
2013Author
Bolton, G.
Moss, S.J.
Sparks, M.
Venter, P.C.
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Background. Shoulder injuries are the most severe injuries in rugby union players, accounting for almost 20% of injuries related to the
sport and resulting in lost playing hours.
Objective. To profile the thoracic posture, scapular muscle activation patterns and rotator cuff muscle isokinetic strength of semi-professional
rugby union players.
Methods. Using the hand-behind-the-neck and -back methods, we manually tested the range of motion (ROM) of the shoulder joints
of 91 uninjured semi-professional rugby union players who consented to participate in the study. Profiling and classification of thoracic
posture was performed according to the New York Posture Test. Activation patterns of the upper and lower trapezius, serratus anterior
and infraspinatus scapular muscles were determined by electromyography. The isokinetic muscle strength of the rotator cuff muscles was
determined at 60°/sec by measuring the concentric and eccentric forces during internal rotation (IR) and external rotation (ER).
Results. Participants presented with non-ideal or unsatisfactory internal (59%) and external (85%) rotators of the shoulder. A slightly
abnormal or abnormal forward head posture was observed in 55% of participants, while 68% had an abnormal shoulder position in the
lateral view. The muscle activation sequence of the rotator cuff muscles was: (i) serratus anterior, (ii) lower trapezius, (iii) infraspinatus, and
(iv) upper trapezius. The isokinetic ER/IR muscle-strength ratio during concentric muscle contraction was 64% (standard deviation (SD)
±14) for the left shoulder and 54% (SD ±10) for the right shoulder. The ER/IR ratio for eccentric muscle contraction was 67% (SD ±12) and
61% (SD ±9) for the left and right shoulders, respectively.
Conclusions. Non-ideal or unsatisfactory flexibility of the external rotators of the shoulder, a forward shoulder posture in the lateral view,
and weakness of the external rotators did not result in an abnormal rotator cuff muscle activation pattern in this study. Postural deviations
may, however, increase the risk of shoulder injury in rugby union players in the long term, and should be corrected
URI
http://hdl.handle.net/10394/16617https://journals.assaf.org.za/index.php/sajsm/article/view/386
https://journals.co.za/doi/pdf/10.10520/EJC132936
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