Psychophysiological stress responses, muscle tension, and neck and shoulder pain among supermarket cashiers.

This study examined psychological and physiological stress, as well as muscle tension and musculoskeletal symptoms, among 72 female supermarket cashiers. Stress levels were found to be significantly elevated at work, as reflected in the catecholamines, blood pressure, heart rate, electromyographic (EMG) activity, and self-reports. Fifty cashiers (70%) suffering from neck-shoulder pain (trapezius myalgia) were found to have higher EMG activity at work and reported more tension after work. Women who kept a diary for 1 week and reported more musculoskeletal pain (above the median) were older, had higher blood pressure, and reported more work stress and psychosomatic symptoms. The elevated stress levels at work are consistent with data from workers involved in other types of repetitive tasks and can be important for the high prevalence of neck and shoulder symptoms among the cashiers.

Psychophysiological stress and EMG activity of the trapezius muscle.

Although it is generally assumed that mental stress induces muscular tension, the experimental data have, so far, been inconclusive. Likely explanations for these inconsistent findings are (a) too small subject samples in some experiments, (b) the use of only one type of stress stimulation, and (c) the lack of objective (physiological) measurements documenting the stress-inducing properties of the experimental treatment. Furthermore. the effect of mental stress and physical load separately, versus the combined influence of physical and mental load on muscular tension, has not been investigated earlier. Therefore, the aim o f the present experiment was lo examine the effects of mental stress as well as of physical load, separately and in combination, on perceived stress, physiological stress responses, and on muscular tension as reflected in electromyographical (EMG) activity of the trapezius muscle. Sixty two female subjects were individually exposed to mental arithmetic, the Stroop color word test (CWT), the cold pressor test, standardized test contractions (TCs), and the CWT combined with a TC. Compared to baseline, the stress session induced significant increases in systolic and diastolic blood pressure, heart rate, urinary catecholamines, salivary cortisol, and self-reported stress. Each of the two mental stress tests induced a significant increase in EMG activity. The CWT caused a rise in EMG activity also during the TC, which was significantly more pronounced than the increase induced by the CWT alone. Blood pressure responses and self-reported stress followed the same pattern as the EMG activity. The results are consistent with the assumption that psychological stress plays a role in musculoskeletal disorders by increasing muscular tension both in low-load work situations and in the absence of physical load. It is also indicated that the stress-induced increase in muscular tension is accentuated on top of a physical load.