Re-entrainment of diurnal variation of psychological and physiological performance at the end of a slowly rotated shift system in hospital workers

Eighteen normal male nurses were tested on a battery of simple psychomotor tasks, subjective self-ratings and physiological tests on three weekly occasions, during the 6th day of each shift (morning, afternoon, night) of their actual job rotation pattern. The shift order was assigned according to a fully balanced design and the tests were carried out between the 3rd and the 5th h from the beginning of work (approximately at 10 a.m., 6 p.m., and 2 a.m.). During the night shift, the subjects rated themselves as most tired and reported higher perceived exertion at different work loads performed on a bicycle ergometer. None of the psychological and physiological variables showed significant inter-shift differences except heart rate and blood pressure: both were lower in the night, the former only at rest and after a light effort, the latter only under hardest work loads. A very high correlation was found between perceived exertion and heart rate in all three shift conditions while a negative correlation between perceived exertion and extraversion emerged in the night occasion only. The present results are discussed and the hypothesis of an adaptation of performance, on most of the tests used, to this weekly rotating shift system is suggested