Reduced scapular muscle control and impaired shoulder joint position sense in subjects with chronic shoulder stiffness

Yang, Jing-lan; Jan, Mei-Hwa; Hung, Cheng-Ju; Yang, Pei-Lin; Lin, Jiu-jenq

doi:10.1016/j.jelekin.2009.04.007

« Previous Next »Journal of Electromyography and Kinesiology
Volume 20, Issue 2 , Pages 206-211, April 2010

Reduced scapular muscle control and impaired shoulder joint position sense in subjects with chronic shoulder stiffness

Jing-lan Yang
- Department of Rehabilitation and Physical Medicine, National Taiwan University Hospital, 100 Taipei, Taiwan
Mei-Hwa Jan
- School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, 100 Taipei, Taiwan
- Physical Therapy Center and Department of Rehabilitation and Physical Medicine, National Taiwan University Hospital, 100 Taipei, Taiwan
Cheng-Ju Hung
- School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, 100 Taipei, Taiwan
Pei-Lin Yang
- School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, 100 Taipei, Taiwan
Jiu-jenq Lin
- School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, 100 Taipei, Taiwan
- Physical Therapy Center and Department of Rehabilitation and Physical Medicine, National Taiwan University Hospital, 100 Taipei, Taiwan
- Corresponding author. Tel.: +886 2 3366 8126; fax: +886 2 3366 8161.

Received 24 October 2008; received in revised form 4 March 2009; accepted 20 April 2009. published online 15 June 2009.

Abstract

The purpose of the present study was to determine (1) if joint position sense (JPS) in subjects with shoulder stiffness (SS) differs from that in controls; (2) if, when JPS is reduced in SS, it is related to scapular muscular activities in the mid/end ranges of motion; and (3) if a person’s function is associated with his or her level of JPS. Eighteen subjects with unilateral SS and 18 controls were included. Each subject performed abduction by self-selecting an end/mid range position. The electromagnetic motion-capturing system collected kinematic data while surface electromyography collected muscle activities (upper trapezius, lower trapezius, and serratus anterior muscles). Subjects were asked to move the upper limb to the target position (end/mid range) accurately without visual guidance. Reduced JPS was observed in subjects with SS (2.7 degrees in mid range, p<0.05). The JPS was enhanced by an increased scapula muscular activation level in the end range of motion (R=−0.61 for SS and −0.41 for controls) and by coordination among muscles’ activation in the mid-range of motion (R=−0.87 for SS and R=−0.53 for controls). Impaired JPS was also related to self-reported functional status (R=−0.56) in subjects with SS. Shoulder JPS in subjects with chronic SS is impaired in comparison with controls. In the mid-range motion, the coordination of scapula muscular activation is related to shoulder JPS. Impaired JPS is also function-related in subjects with SS. These findings suggest that the coordination among scapula muscles’ activation were important to consider in the rehabilitation of patients with chronic SS.