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Muscle activation patterns in shoulder impingement patients

Muscle activation patterns in shoulder impingement patients

Strickland, Jennifer, Goss-Sampson, Mark ORCID: 0000-0002-2662-559X and White, Trina (2009) Muscle activation patterns in shoulder impingement patients. In: Loland, S., Bø, K., Fasting, K., Hallén, J., Ommundsen, Y., Roberts, G. and Tsolakidis, E., (eds.) Book of Abstracts of the 14th Annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009. European College of Sport Science, Oslo, Norway, p. 290. ISBN 9788250204201

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Introduction: Shoulder impingement is one of the most common presentations of shoulder joint problems 1. It appears to be caused by a reduction in the sub-acromial space as the humerus abducts between 60o -120o – the 'painful arc'. Structures between the humeral head and the acromion are thus pinched causing pain and further pathology 2. Shoulder muscle activity can influence this joint space but it is unclear whether this is a cause or effect in impingement patients. This study aimed to observe muscle activation patterns in normal and impingement shoulder patients and determine if there were any significant differences.
Method: 19 adult subjects were asked to perform shoulder abduction in their symptomatic arm and non-symptomatic. 10 of these subjects (age 47.9 ± 11.2) were screened for shoulder impingement, and 9 subjects (age 38.9 ± 14.3) had no history of shoulder pathology. Surface EMG was used to collect data for 6 shoulder muscles (Upper, middle and lower trapezius, serratus anterior, infraspinatus, middle deltoids) which was then filtered and fully rectified. Subjects performed 3 smooth unilateral abduction movements at a cadence of 16 beats of a metronome set at 60bpm, and the mean of their results was recorded. T-tests were used to indicate any statistical significance in the data sets. Significance was set at P<0.05.
Results: There was a significant difference in muscle activation with serratus anterior in particular showing a very low level of activation throughout the range when compared to normal shoulder activation patterns (<30%). Middle deltoid recruitment was significantly reduced between 60-90o in the impingement group (30:58%).Trends were noted in other muscles with upper trapezius and infraspinatus activating more rapidly and erratically (63:25%; 60:27% respectively), and lower trapezius with less recruitment (13:30%) in the patient group, although these did not quite reach significance.
Conclusion: There appears to be some interesting alterations in muscle recruitment patterns in impingement shoulder patients when compared against their own unaffected shoulders and the control group. In particular changes in scapula control (serratus anterior and trapezius) and lateral rotation (infraspinatus), which have direct influence on the sub-acromial space, should be noted. It is still not clear whether these alterations are causative or reactionary, but this finding gives a clear indication to the importance of addressing muscle reeducation as part of a rehabilitation programme in shoulder impingement patients.

Item Type: Book Section
Additional Information: This abstract forms part of the book of abstracts from the 14th Annual Congress of the European College of Sport Science, held 24-27 June 2009, Oslo, Norway.
Uncontrolled Keywords: shoulder impingement, shoulder joint, abduction, muscle activation,
Subjects: R Medicine > RM Therapeutics. Pharmacology
Faculty / School / Research Centre / Research Group: Faculty of Education, Health & Human Sciences > School of Human Sciences (HUM)
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Last Modified: 09 Oct 2021 04:46

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