Variations of physiological functions and psychological measures and their relationships on delayed shift of sleeping time

The variations of sublingual temperature, pulse rate, flicker fusion frequency (CFF), subjective fatigue feelings (SFF) and 8 selected reaction times and the relationships between them were examined in six university students under the condition of successive 6-h delayed shift with 8 sleeping h and 22 waking h for 6 d. SFF was measured by the scales proposed by the Japanese Society for Industrial Fatigue Research. On the 2nd d when the shifting was started after the subjects had slept from 00:00 to 08:00 and on the 3rd d after sleeping h of 06:00 to 14:00, the variations of sublingual temperature, pulse rate and CFF showed a pattern of circadian rhythm. However, on the 4th-5th d the rhythms of sublingual temperature and pulse rate were flattened. On the other hand, CFF demonstrated a variation of having a nearly constant tendency till 08:00, followed by a gradual decrease during the daytime. The variation of SFF (the scale of "sleepiness and dullness") was similar to that of CFF, although the change of the score was in the opposite direction. On the 3rd-4th d, the 4th-5th d and the 6th d, significantly high rank correlations were observed between sublingual temperature and pulse rate and between CFF and SFF. However, between sublingual temperature and CFF, a high correlation which was observed on the 1st and the 2nd d was not seen on the 4th-5th and 6th d. Eight selected reaction times were shortened during the experimental days, but there was no consistent pattern of variation within these days. The results of the experiment showed that the relationship between CFF and SFF exists during the daytime when the arousal level is low.