Twenty-four-hour patterns in human performance, subjective and physiological variables and differences between morning and evening active subjects.

A study was undertaken to investigate differences between habitually morning active and evening active subjects as regards 24-hr patterns in physiological and subjective arousal and performance efficiency under conditions of 72 hr of sleep deprivation. The results were that very consistent 24-hr rhythmic were present in some of the performance variables, subjective alertness, oral temperature and urinary adrenaline excretion. No significant differences in 24-hr patterns could be detected between a group of habitually morning active and a group of evening active subjects. Significant correlations were obtained between oral temperature and some of the performance measures, while adrenaline excretion was not significantly correlated with performance. There were rather high correlations between subjective alertness ratings and some of the performances.