Abstract
The aim of this study was to compare the circadian variation of circulatory functions in physically average and very fit male dayworkers. Six physical very fit (group I, O2 max 57.4ml/kg/min) and six average fit (group II, mean O2 max 34.6ml/kg/min) railroad workers, mean age 32.1, were measured at 0200, 0600, 1000, 1400, 1800 and 2200 hours during a period of eight weeks. Mean group values were calculated according to the periodic regression analysis for harmonic intensities, and day and night mean values were compared with a paired t-test. In group I, heart rate at rest and at work and the ratings of perceived exertion were lower and the recovery of heart rate after work was faster both during the day and night than in group II. In the daytime, the reaction time was shorter in group I than in group II. At nighttime, the oral temperature was lower in group I than in group II. The amplitude of most of the variables was greater and the day-night differences became more pronounced in group I than in group II. The results indicate that there are rather constant differences in the physiological responses between the physically average and very fit male subjects throughout the circadian period. The lower responses to work, the faster recovery after work and the larger amplitude of physiological functions among very fit people suggest that they can better tolerate shiftwork.
