Shoulder Muscular Activity During Isometric Three-Point Kneeling Exercise on Stable and Unstable Surfaces

in Journal of Applied Biomechanics
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The purpose of this study was to determine if performing isometric 3-point kneeling exercises on a Swiss ball influenced the isometric force output and EMG activities of the shoulder muscles when compared with performing the same exercises on a stable base of support. Twenty healthy adults performed the isometric 3-point kneeling exercises with the hand placed either on a stable surface or on a Swiss ball. Surface EMG was recorded from the posterior deltoid, pectoralis major, biceps brachii, triceps brachii, upper trapezius, and serratus anterior muscles using surface differential electrodes. All EMG data were reported as percentages of the average root mean square (RMS) values obtained in maximum voluntary contractions for each muscle studied. The highest load value was obtained during exercise on a stable surface. A significant increase was observed in the activation of glenohumeral muscles during exercises on a Swiss ball. However, there were no differences in EMG activities of the scapulothoracic muscles. These results suggest that exercises performed on unstable surfaces may provide muscular activity levels similar to those performed on stable surfaces, without the need to apply greater external loads to the musculoskeletal system. Therefore, exercises on unstable surfaces may be useful during the process of tissue regeneration.

Rodrigo Cappato de Araújo (Corresponding Author) is with the Department of Physical Therapy, University of Pernambuco, Recife, BR-PE, Brazil. Rodrigo de Andrade, Helga Tatiana Tucci, Jaqueline Martins, and Anamaria Siriani de Oliveira are with the Department of Biomechanics, Medicine, and Locomotor Rehabilitation Apparatus, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, BR-SP, Brazil.