Electromyogram and perceived fatigue changes in the trapezius muscle during typewriting and recovery

Abstract

The purpose of the present study was to investigate the development and recovery of muscle fatigue in the upper trapezius muscle by analyzing electromyographic signals. Six male subjects performed a simulated typewriting task for four 25-min sessions. During fatigue and the following rest periods, subjective fatigue and surface electromyography (EMG) from the trapezius muscle during isometric contraction at 30% maximum voluntary contraction (MVC) were periodically measured in the interval. We detected a significant decrease in muscle fiber conduction velocity (MFCV) (P = 0.008) and median frequency (MDF) (P = 0.026) as well as an increase in root mean square (RMS) (P = 0.039) and subjective fatigue (P = 0.0004) during the fatigue period. During the recovery period, subjective fatigue decreased drastically and significantly (P = 0.0004), however, the EMG parameters did not recover completely. Thus, physiological muscle fatigue in the trapezius developed in accordance with subjective muscle fatigue during typewriting. On the other hand, differences between the physiological and subjective parameters were found during recovery. Further studies should be necessary to reveal the discrepancy could be a major factor of a transition from temporal phenomena to serious chronic muscle fatigue and to identify the necessity of some guidelines to prevent VDT work-related chronic muscle fatigue in the trapezius.

Cervical flexion–relaxation response to neck muscle fatigue in males and females

“…Repetitive arm and neck exertions are also known to contribute to the fatigue of the neck muscles Hagberg, 1981;Hansson et al, 1992). Some studies have also shown an active contribution by the neck muscles during forceful arm exertions leading to the fatigue (Kimura et al, 2007;Nimbarte, 2014;Nimbarte et al, 2012Nimbarte et al, , 2013Troiano et al, 2008).…”

Assessment of force and fatigue in isometric contractions of the upper trapezius muscle by surface EMG signal and perceived exertion scale

“…The use of surface EMG techniques in ergonomic studies has been documented in different tasks, including repetitive work at a car assembly line [12], work at the visual display terminal [13], and other studies [1]. In occupational health, upper trapezius (UT) muscle is usually investigated by surface EMG, as it is a superficial muscle and its activity is influenced by neck or shoulder pain [14].…”

The time course of autonomic parameters and muscle tension during recovery following a moderate cognitive stressor: Dependency on trait anxiety level

“…It should be noted that recovery time is different in the trapezius muscle and the gastrocnemius muscle following the stressful task. This different recovery time could depend on muscle types and could be related to firing rate modulation of motor units or biochemical changes in metabolites (Kimura et al, 2007).…”