OBJECTIVE The objective of the present study was to develop a numerical model of the shoulder able to quantify the influence of the shape of the humeral head on the stress distribution in the scapula. The subsequent objective was to apply the model to the comparison of the biomechanics of a normal shoulder (free of pathologies) and an osteoarthritic shoulder presenting primary degenerative dise...

The main purpose was to analyze quantitatively the the average surface EMGs of the muscles that function around the elbow and shoulder joints of both arms in bimanual "rowing" movements, which were produced under identical elastic loads applied to the levers ("oars"). The muscles of PM group ("pulling" muscles: elbow flexors, shoulder extensors) generated noticeable velocity-dependent dynamic E...

BACKGROUND Shoulder pain is reported to be highly prevalent and tends to be recurrent or persistent despite medical treatment. The pathophysiological mechanisms of shoulder pain are poorly understood. Furthermore, there is little evidence supporting the effectiveness of current treatment protocols. Although myofascial trigger points (MTrPs) are rarely mentioned in relation to shoulder pain, the...

Proprioception is essential for shoulder neuromuscular control and shoulder stability. Exercise of the rotator cuff and scapulothoracic muscles is an important part of shoulder rehabilitation. The purpose of this study was to investigate the effect of rotator cuff and scapulothoracic muscle exercises on shoulder joint position sense. Thirty-six healthy subjects were recruited and randomly assig...

[Purpose] This study aimed to clarify activation of the infraspinatus and scapular stabilizing muscles during shoulder external rotation at various shoulder elevation angles. [Subjects] Twenty subjects participated in this study and all measurements were performed on the right shoulder. [Methods] Isometric shoulder external rotation strength and surface electromyographic data were measured with...

Many studies have demonstrated that muscle activity 50-100 ms after a mechanical perturbation (i.e., the long-latency stretch response) can be modulated in a manner that reflects voluntary motor control. These previous studies typically assessed modulation of the long-latency stretch response from individual muscles rather than how this response is concurrently modulated across multiple muscles...

BACKGROUND Muscles are important "sensors of the joint instability". The aim of this study was to identify the neuro-motor control strategies adopted by patients with anterior shoulder instability during overhead shoulder elevation in two planes. METHODS The onset, time of peak activation, and peak magnitude of seven shoulder muscles (posterior deltoid, bilateral upper trapezius, biceps brach...

This study was performed to determine the changes in electromyographic activities in the shoulder and forearm muscles when using the bare hands, well-fitting gloves, and gloves that are one size smaller or one size larger for simulated assembly operations. Sixteen asymptomatic seated workers with normal hands and no obvious deformities, skin diseases, or allergies were recruited. The subjects w...

BACKGROUND Functional shoulder instability (polar type III) is caused by underactivity of rotator cuff and periscapular muscles, which leads to subluxation or dislocation during shoulder movement. While surgical treatment has shown no benefits, aggravates pain, and frequently diminishes function even further, conservative treatment is often ineffective as well. OBJECTIVES The aim was to inves...

The purpose of this review is to scrutinize the physiology of neck-shoulder pain and trapezius myalgia based on the most recent scientific literature. Therefore, systematic literature searches have been conducted. Occurrence of neck-shoulder pain, risk factors for development of neck-shoulder pain, and its work-relatedness are addressed. Furthermore, the latest information on the biochemical mi...