Trapezius muscle EMG as predictor of mental stress

Abstract

Stress is a growing problem in society and can, amongst others, induce musculoskeletal complaints, related to sustained muscle tension. The ability to measure stress with a wireless system would be useful in the prevention of stress-related health problems. The aim of this experiment was to derive stress levels of subjects from electromyography (EMG) signals of the upper trapezius muscle. Two new stress tests were designed for this study, which aimed at creating circumstances that are similar to work stress.An experiment is described in which EMG signals of the upper trapezius muscle were measured during three different stressful situations. Stress tests included a calculation task (the Norinder test), a logical puzzle task and a memory task, of which the last two were newly designed.The results show significantly higher amplitudes of the EMG signals during stress compared to rest and fewer gaps (periods of relaxation) during stress. Also, mean and median frequencies were significantly lower during stress than during rest. The differences in EMG features between rest and stress conditions indicate that EMG is a useful parameter to detect stress. These results show opportunities for the inclusion of EMG sensors in a wireless system for ambulatory monitoring of stress levels.