Mechanical performance and electromyography during repeated maximal isokinetic shoulder forward flexions in female cleaners with and without myalgia of the trapezius muscle and in healthy controls

Abstract

This cross-sectional study aimed at investigating the influence of occupational exposure to static and highly repetitive work involving the neck and shoulder muscles, myalgia of and tender point in the trapezius muscle on biomechanical output, and electromyogram (EMG) variables (mean frequency MNF, signal amplitude and ability to relax) during maximal forward flexions of the shoulder muscles. Groups of 25 cleaners suffering from chronic myalgia of the trapezius muscle, 25 cleaners free from myalgia of the trapezius muscle and 21 teachers performed 150 forward flexions using an isokinetic dynamometer. Perception of fatigue was reported and surface EMG was recorded from four muscles during the endurance test. The cleaners were stronger than the teachers. Myalgia was associated with lower levels of endurance and a high degree of perceived fatigue. The ability to relax the trapezius muscle decreased with age and was even lower in cleaners with and without myalgia. Higher MNF of the deltoid muscle but not of the trapezius muscle was found in the group suffering from myalgia compared to the groups free from myalgia. This cross-sectional study indicated that myalgia of the trapezius muscle did not influence the strength but did influence the endurance of the forward flexor muscles of cleaners. The observed decrease in the ability to relax the trapezius muscle in cleaners compared to healthy teachers might be indicative of a future insufficiency in the muscle. Prospective studies are needed to define the significance of the results presented here.

Assessment of patients with neck pain: a review of definitions, selection criteria, and measurement tools

“…75 In subjects with neck pain, self-reported pain and disability ratings showed no correlation with strength measurements. 29,75,82 One study evaluated neck muscle endurance in patients with WAD compared with age-matched healthy controls. 83 Cervical flexor endurance tested in a supine position could distinguish well between WAD patients and the controls.…”

“…Muscle endurance measurement by electromyography for repeated forward flexion of the arm tested in people with neck pain and myalgia compared with symptom-free subjects was significantly lower. 82 …”

Bilateral Changes in Forearm Oxygen Consumption at Rest and After Exercise in Patients With Unilateral Repetitive Strain Injury: A Case-Control Study

“…Another hypothesis is related to an impaired ability to relax muscles in patients with RSI. 5,14,33 Veiersted et al 33 found that healthy women with lower rates of brief unconscious interruptions in muscle activity, monitored with electromyography, were prone to develop RSI symptoms over time. The finding suggests that continuous muscle activation during muscle tasks is a predisposing factor for the development of RSI symptoms.…”

Effects of Hot Water Baths Containing Carbon Dioxide and 3-Octylphthalide on Work-Related Chronic Shoulder-Neck Muscle Pain

“…These shoulder-neck symptoms are generally classified into symptomatic and essential groups, with and without etiological factors such as orthopedics and medical disorders. Essential shoulder-neck pain is considered to develop and be exacerbated by corresponding muscle fatigue and hindered microcirculation due to repetitive tension of the shoulder-neck muscles 1,2) . Increases in both mental and physical stresses because of the recent increase in the popularity of information technology devices and the modification of the workplace environment are thought to be predominantly responsible for the increase in shoulder-neck problems.…”