RESEARCH ARTICLE


Kinematic Differences between Two Types of Forward Elevations of the Shoulder Joint: Flexion and Reaching Elevation



Ryo Sahara1, Junichiro Hamada2, *, Kunio Yoshizaki1, Kazuhiro Endo1, Daisuke Segawa1, Mitsukuni Yamaguchi3
1 Department of Rehabilitation, Kuwano Kyoritsu Hospital, 2-9-18 Shima, Koriyama, Fukushima, Japan
2 Department of Orthopaedic Surgery, Kuwano Kyoritsu Hospital, 2-9-18 Shima, Koriyama, Fukushima, Japan
3 Therapy Laboratory, 1-1-5-201 Tsuchihashi, Miyamae-ku, Kawasaki, Kanagawa, Japan


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Creative Commons License
© 2020 Sahara et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Orthopaedic Surgery, Kuwano Kyoritsu Hospital, Zip cord 963-8034, Address 2-9-18 Shima, Koriyama, Fukushima, Japan; Tel: +81-24-933-5422; Fax: +81-24-923-6169; E-mail: i-hamada@koriyama-h-coop.or.jp


Abstract

Background:

Extension of the elbow joint is maintained during shoulder flexion. In contrast, the arm starts from the flexed position of the elbow joint and the joint gradually extends during reaching elevation.

Objectives:

This study aimed to compare the kinematic elements and electromyographic (EMG) activities of the rotator cuff muscles between flexion and reaching elevation.

Methods:

The study included 10 healthy young men. (average age, 21.5 ± 3.4 years), and measurements were performed on their dominant arms. A three-dimensional motion analyzer was used to record the following elements during shoulder flexion and reaching elevation: the angles of glenohumeral joint elevation and scapular upward rotation, scapulohumeral rhythm, external rotation of the humerus, and glenohumeral plane shifting from the coronal plane. The EMG activities in the supraspinatus, infraspinatus, subscapularis, and teres minor were recorded simultaneously.

Results:

The plane of reaching elevation was retained at 60° from the coronal plane. The glenohumeral planes (P < 0 .01) and the external rotation angles of the humerus below 90° of elevation (P < 0.05) were significantly different between both the motions. The EMG activities in the supraspinatus (P < .01), infraspinatus (P < 0.05), and teres minor (P < 0.01) were significantly lower while reaching elevation than those during flexion.

Conclusion:

The motion plane at 60° from the coronal plane, movement of the humeral external rotation, and EMG activities of the rotator cuff muscles were different during reaching elevation and shoulder flexion.

Keywords: Shoulder joint, Flexion, Reaching elevation, 3-dementional motion analysis, Rotator cuff muscles, Electromyography.