Irregularity of rest and activity: studies on circadian rhythmicity in man.

Abstract

SUMMARY1. Rectal temperature, electrolyte excretion and performance were studied in young adults who followed an irregular pattern of work and rest for 9 days in an isolation unit.2. In the analysis, effects evoked by the pattern of work and rest were separated from the oscillatory component, and rhythms for individual days were examined by the cosinor method.3. During the schedule, rhythms no longer showed a period of exactly 24 h, and this effect was confirmed by studies using a repeated cycle of irregular work and rest and by studies using constant routines.4. Temperature and urinary constituents differed in the strength and phase of their rhythms when corrected for evoked effects, as well as in the strength of the evoked effects themselves.5. There was evidence of deterioration in performance during work periods which exceeded 9 h, but there was no evidence of progressive deterioration in performance over the 9 day schedule.

Sports performance: is there evidence that the body clock plays a role?

“…This method can remove eVects due to the environment and separate out those due to the body clock and time awake, but it is time-consuming and arduous to perform. (e) Protocols involving changed sleep times: These protocols have been used mainly with measures of cognitive performance (Åkerstedt et al 1993Minors et al 1986;Waterhouse et al 2001). Their rationale is that, if external conditions are standardised, then performance is the combined result of circadian time (which follows a sinusoid parallel to core temperature) and the homeostatic time-since-waking factor (which declines exponentially).…”

The role of naps in alleviating sleepiness during an irregular sleep-wake schedule

“…There appear to be few comparable measurements in the scientific literature. Our own earlier studies (Minors et al 1986) indicate an increase of about 28% in sleepiness between 6 h (estimated by interpolation) and 13-1 7 h of being awake.…”

“…Thus it is viable to attempt to compare the size of the different factors causing sleepiness and this was the reason why the mathematical model was developed (based on Minors et al 1986). Table 2 enables a comparison of the size of the different factors to be made.…”

“…The isolation unit in which the experiments were performed and the general protocol have been described in detail previously (Elliott et al 1972;Minors et al 1986). Briefly, after four control days during which subjects lived a regular and conventional lifestyle, (sleep 00.00-08.00 h), an irregular sleep-wake schedule lasting nine days was undertaken (figure 1).…”

“…We have previously performed a series of experiments in an isolation unit in which individuals were subjected to an irregular sleep-wake schedule (Minors et al 1986). Measurements of several physiological variables, of performance at a variety of tasks and of a number of self-assessments including sleepiness were made.…”