The effect of high ambient temperature on the adjustment of operators to fast rotating 12-hour shiftwork.

The aim of the investigation was to study the effect of high ambient temperature (HAT) on the adjustment to fast rotating 12-h shifts by following the time-of-day variations of certain circadian and stress indicators. We investigated 12 male HAT operators and 21 individuals working in normal ambient temperature (NAT) in a thermoelectric power plant. The shift system of both groups comprised an 8-day cycle of 2 shifts per day (day shift: 0700 to 1900; night shift: 1900 to 0700), with 2 successive days of the same shift followed by 2 days off. We followed variations in oral temperature, 11-oxycorticoids, as well as catecholamines adrenaline and noradrenaline excretion at 4-h intervals during 2 day and 2 night shifts. Our data show daily oriented circadian rhythms of operators working on fast rotating 12-h shifts in conditions of HAT and NAT. Reduced general activation was observed in the second half of the prolonged 12-h night shifts, more pronounced in HAT operators. The stress indicators investigated here showed a stress reaction in HAT operators at the beginning of the first day shift. Both prolonged 12-h shifts and high ambient temperature impose extra demands and may have an impact on the performance and work safety of the operators.

Variations in 6-sulphatoxymelatonin excretion and oral temperature under a 12-hour shiftwork environment.

The aim of the present study was to follow the time-of-day variations in oral temperature and the excretion of a melatonin metabolite, 6-sulphatoxymelatonin (aMT6s), in individuals working fast-rotating, 12-h day and night shifts in a thermoelectric power station. Twenty-three male operators working on a 12-h-shift system (two successive days of the same shift: 0700-1900; 1900-0700, followed by two days off) were investigated. Oral temperature and aMT6s were measured at 4-h intervals on the second day shift and on the first and second night shifts. Clearly expressed "peaks" and "troughs" in aMT6s excretion and in oral temperature were found, indicating that a typical diurnal pattern of variation was preserved during fast-rotating, 12-h-shift work. The differences between the first and the second night shift in the examined parameters, particularly in aMT6s, can be attributed to the changes in sleep time between the two work shifts.

Changes in some biochemical and physiological indexes after hypergravitation.

The purpose of this study was to assess the G-tolerance and G-induced changes in plasma renin activity (PRA), serum cortisol, testosterone, thyroid hormones and blood concentrations of serotonin and histamine. Experiments were performed on 26 student pilots aged 22.7 +/- 0.7 years using simulated aerial combat manoeuvres (SACM) in a centrifuge with radius 7.5 m. G-tolerance was assessed by loss of vision criteria, G-induced loss of consciousness and significant disturbances in heart rhythm. PRA, cortisol, testosterone and thyroid hormones were measured by radioimmunoassay, serotonin and histamine by spectrofluorimetric methods 24 hours before and 5 min after SACM. The statistical significance of hypergravitation and G-tolerance were determined by ANOVA. We found a significant increase in PRA (p = 0.001) and thyroxine concentration (p = 0.005) after hypergravitation loads. It is known that these changes are indicative for cardiovascular adaptation and enhancement of energy mobilization. Histamine levels differed significantly by G-tolerance (p = 0.031), while serotonin concentrations changed by hypergravitation (p = 0.004). Significant dependence on hypergravitation x G-tolerance was found for serotonin values (p = 0.024). Studying G-induced hormonal changes can reveal individual peculiarities in G-tolerance, a limiting factor for the exploitation of high performance aircraft.