The purpose of this study was to reveal the peculiarities of subjective and objective measurements of stress in the mental activity of shiftworkers. The study subjects were electricity distribution network controllers, whose work is characterised by having to deal with many unpredictable situations that may affect their ability to provide a continuous supply of electricity for consumers.

In total, 17 controllers were examined, all of whom worked 12-hour shifts under a two-day shift rotation. Over a three-week period, the following variables were measured in controllers at two-hour intervals during their working shifts: systolic and diastolic blood pressure, and heart rate. A total of 1,224 subject observations was acquired. Haemodynamic parameters, including age and anthropometric data, were calculated for each observation [1,2], and measurements of short-term memory [3] and attention [4] were acquired at the beginning and end of each shift. At the end of every shift, subjects were asked to estimate the level of stress they perceived that they had experienced over that shift using a 5-point scale, where 1 represented very low stress and 5 very high stress.

All parameters studied were recalculated as a percentage of the overall mean, owing to the individual nature of the data. ANOVA and MANOVA were performed, and Pillai's criterion was used to test the significance of any effect of stress on the parameters studied. Diastolic blood pressure and attention were shown to be the most sensitive to stress. The effect of stress on cognitive performance and the cardiovascular system was most pronounced during the first day shift, and less pronounced during the first night shift. It was suppressed during the second consecutive shift. It was also shown that subjective stress evaluation does not accurately reflect the psychophysiological body response, and hence should not be treated as a sufficient measure of stress on its own.

In conclusion, this complex approach to measuring stress can be recommended, using both subjective scores and psychophysiological measurements, as well as accompanying information (e.g. the type of shift) and complex computer-based data processing.

References

1. Arinchin, N.I.; Kulago, G.V. (1969). Hypertonic disease as a disturbance in blood circulation self-regulation. Minsk: Nauka i Tekhnika.
2. Khramov, Y.A.; Veber V.R. (1985). Vegetative maintenance and haemodynamics under hypertonic disease. Novosibirsk: Nauka.
3. Makarenko, N.V.; Pukhov, V.A.; Kolchenko, N.V.; Majdikov, J.L.; Kiyenko, V.M.; Voronovskaja, V.I. (1987). Bases of the professional psychophysiological selection. Kiev: Naukova Dumka.
4. Majdikov, J.L.; Makarenko, N.V.; Petlenko, J.A.; Gerasimov, A.V.; Kolchenko, V.M.; Omelchenko, A.A. (1985). Psychophysiological methods and criteria for the estimation of the professional activity success of the HPPs' operative personnel. Kiev: Methodical Recommendations.

Paper presented at Measuring Behavior 2002 , 4^th International Conference on Methods and Techniques in Behavioral Research, 27-30 August 2002, Amsterdam, The Netherlands

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