Perceived fatigue after mental work: an experimental evaluation of a fatigue inventory

The aim of this study was to investigate the perceived fatigue after mental work and to test the Swedish Occupational Fatigue Inventory (SOFI). Twenty male and 20 female participants worked with proof reading (2 x 90 min) and a vigilance task (2 x 60 min). After each task session, perceived fatigue was rated with the SOFI and Borg's CR10O-scale. In addition, physiological reactions were registered; blood pressure, heart rate, heart rate variability and muscle activity in corrugator supercilii, as well as measures of performance: reaction time, number of pages read and number of proof errors found, number of detected signals. As expected, the highest ratings were obtained on Lack of energy, Lack of motivation and Sleepiness, particularly after the vigilance task. High ratings after both work tasks were also found on the CR10-scale. Men and women did not differ significantly with respect to their ratings. No clear-cut physiological reactions were found to correlate with ratings of fatigue. The results indicate the validity of the mental dimension of the SOFI.