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C. Bascour-Sandoval1,2, R. Gajardo-Burgos3, G. Galvéz-García4,5, M. Barramuño2
1Universidad de La Frontera, Departamento de Medicina Interna, Temuco, Chile, 2Universidad Autónoma de Chile, Carrera de Kinesiología, Temuco, Chile, 3Universidad Austral de Chile, Instituto de Aparato Locomotor y Rehabilitación, Valdivia, Chile, 4Universidad de La Frontera, Departamento de Psicología, Temuco, Chile, 5Université Lyon 2, Département de Psychologie Cognitive & Neuropsychologie, Institut de Psychologie, Laboratoire d’Étude des Mécanismes Cognitifs, Lyon, France
Background: To add of adduction pressure on the biofeedback unit during glenohumeral external rotation exercises is widely used during physical rehabilitation, in order to promote muscle synergy in the scapulohumeral muscles. Nevertheless, the effect of adduction on muscle activity is controversial. This could be explained by the amount of pressure and/or position while carrying out external rotation.
Purpose: The aim of this study was to evaluate the effect of carrying out adduction during external rotation exercises in low and high shoulder positions on the electromyographic (EMG) activity of the infraspinatus (IS), middle deltoid (MD) and posterior deltoid (PD) muscles.
Methods: EMG activity of the IS, MD and PD muscles was evaluated in 20 healthy participants. Subjects performed 6 ER exercises that combined two factors: i) different adduction pressures on a biofeedback unit (0, 5 and 10 mmHg), and ii) low and high shoulder position. The pressure was controlled using a biofeedback unit. The low and high shoulder positions consisted in 20° and 90° of abduction.
Results: In low shoulder position, the activity of the IS muscle increased as the pressure on the biofeedback unit increased and the MD and PD muscles presented the higher activity at 10 mmHg. In high shoulder position, the activity of the IS muscle was higher at 0 and 10 mmHg, the MD muscle presented higher activity at 5 mmHg, and PD muscle activity did not vary with the pressure.
Conclusion(s): The addition of adduction at a pressure of 5 mmHg in low shoulder position promotes IS muscle activity. Likewise, adduction at a pressure of 10 mmHg will promote activity of the IS, MD and PD.
Implications: This exercise can be used in early stages of rehabilitation to increase the activity of the IS while maintaining the activity of the deltoids.
Funding, acknowledgements: This study was financed by Universidad de La Frontera grant DI20-0046.
Keywords: Electromyography, Exercises, Shoulder
Topic: Musculoskeletal: upper limb
Did this work require ethics approval? Yes
Institution: Universidad de La Frontera
Committee: Comité Ético Científico de la Universidad de La Frontera
Ethics number: 008/20
All authors, affiliations and abstracts have been published as submitted.
