Berckmans K1, Castelein B1, Borms D1, Palmans T1, Parlevliet T2, Cools A1
1Ghent University, Rehabilitation Sciences and Physiotherapy, Gent, Belgium, 2University Hospital Ghent, Physical Medicine and Orthopaedic Surgery - Faculty of Medicine, Gent, Belgium

Background: Shoulder complaints are common in our population. Possible underlying reasons are scapular dyskinesia and a change in muscle pattern activation. In rehabilitation programs, exercises are often prescribed to prevent or heal the poor scapular kinematics and activate the scapular muscles in a proper way. A lot of research has been done to gain information about the activity of scapular muscles while performing exercises. The use of surface electrodes was preferred in most studies for the electromyography of the superficial scapular muscles. However, limited information exists about the activity of the deeper layer of the scapular muscles measured with fine-wire electrodes. Moreover, little is known about the 3D kinematics of the scapula in combination with muscle recruitment patterns during shoulder exercises.

Purpose: The aim of this study is to report combined scapular kinematics with scapulothoracic muscle activity by use of the surface as well as fine wire electrodes during the performance of low load shoulder exercises in healthy people.

Methods: The muscle activity of 8 scapulothoracic muscles was measured in 13 subjects in combination with the measurements of 3D-kinematics of the scapula with a motion capture system (Qualisys).
For the 3 parts of the trapezius (upper (UT), middle (MT), lower (LT)) and serratus anterior (SA), bipolar surface electrodes were used. The fine-wire electrodes were placed under the guidance of ultrasound in following muscles: the levator scapulae (LS) , rhomboid (Rm), infraspinatus (IS) and pectoralis minor (Pm).
The 3D-kinematics and muscle activity was measured during four shoulder exercises (inferior glide, low row, robbery and lawn mower). The sequence was randomly allocated. An ANOVA for repeated measures with Bonferroni correction was applied for statistical analysis.

Results: The functional exercises (lawn mower and robbery) show significantly (p 0.05) more activation of the MT and RM in comparison with the isometric exercises (inferior glide and low row). The LS and UT are significantly more active during the robbery exercise compared to the isometric exercises (p 0.05), although only the low row for the UT (p 0.05). The kinematics of the scapula reveal an internal rotation for all exercises, despite the inferior glide. The scapula performs more downward rotation during the functional exercises compared to more upward rotation during the isometric exercises. Furthermore, the low row shows significantly (p 0.001) more anterior tilt comparing all three other exercises. The scapula is moving towards anterior tilt during the lawn mower and low row, on contrary to the robbery and inferior glide where the scapula is moving in posterior tilt direction.

Conclusion(s): These results confirm specific scapular movements and muscle activation patterns of the surface EMG as well as fine-wire EMG depending the exercises.

Implications: This information gives a physiotherapist the possibility to adapt a rehabilitation program to the needs of a patient. Although, the tentative results should be interpreted with caution when extended to a shoulder patient population.

Keywords: Scapula kinematics, EMG, Shoulder exercises

Funding acknowledgements: The work was unfunded.

Topic: Musculoskeletal: upper limb; Outcome measurement

Ethics approval required: Yes
Institution: Ethical Committee of Ghent University Hospital
Ethics committee: Ethical Committee of Ghent University Hospital
Ethics number: B670201629881

All authors, affiliations and abstracts have been published as submitted.

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