The Effect of Season and Light Intensity on the Core Interthreshold Zone

Mekjavic

2017

J Physiol Anthropol

Self Cite

BackgroundThe core interthreshold zone (CIZ) is defined as the range between temperatures at the onset of shivering and sweating. Its circadian or diurnal variation has not been extensively studied. The present study examined whether the CIZ is subject to a diurnal rhythm. In addition, according to the previous finding that the CIZ was proportionally correlated with peripheral interthreshold zone (PIZ), it was also examined whether cutaneous sensation threshold zone (CSZ), a determinant of the PIZ, is correlated with the CIZ.MethodsThe CIZ and the CSZ were measured in ten Japanese men who underwent three experiments in a single day on the morning, afternoon, and evening in the 2014 experiment (so-called single-day experiment) and six Japanese men underwent the same experiments on the morning of day 1, the afternoon of day 2, and the evening of day 3 in the 2015 experiment (so-called multiple-day experiment). Air temperature was controlled at 20–24 °C. Each subject wore a suit perfused with 25 °C water at a rate of 600 cm3/min and exercised on an ergometer at 50% of their maximum work rate for 10–15 min until their rate of sweating increased. They then remained seated without exercising until their oxygen uptake increased. Rectal temperature, skin temperatures at seven sites, the sweating rate at the forehead, and oxygen uptake were continuously monitored throughout experiment. Cutaneous warm and cold sensation thresholds at three sites were measured using 1- and 2-cm2 probes.ResultsThe results from the single-day experiment demonstrated a small change in the CIZ and core temperature prior to exercise (T c-init) whereas those from the multiple-day experiment demonstrated continuous increase in the CIZ and T c-init. The CSZ measured with a 1-cm2 probe was inversely proportional to the average skin temperature at three sites prior to measurement (T sk-av).ConclusionThe results suggested that the CIZ may be not dependent on time of a day but Tc-init per se and may not be associated with the CSZ.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Diurnal variation in the core interthreshold zone and its relation to cutaneous sensation threshold zone

Mekjavic

2017

J Physiol Anthropol

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“…Because the effect of lighting and season on the CIZ was confirmed in a previous study 5 , luminance was carefully controlled at 1,000 lx, and all experiments were conducted from August to September, as described in the experimental protocol of our previous study 7 .…”

Section: Experimental Protocolmentioning

confidence: 99%

“…Since both the T c and mean skin temperature contribute to the control of sweating and shivering, constant is required to be independent of thermal responses due to changes in Although three different experimental methods have been proposed to keep constant 1,2,3 , Kakitsuba et al 4 devised an alternative method using water-perfused suits, following the method proposed by Mekjavic et al 3 , and demonstrated a seasonal change in the CIZ, and light dependence of the CIZ, which indicated the possible incorporation of a non-visual pathway into the human thermoregulation 5 .…”

Section: Introductionmentioning

confidence: 99%

Diurnal Variation in the Core Interthreshold Zone in Women and its Sex Difference

Mekjavić

2018

IPJ

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“…A constant mean skin temperature (

{\overset{true¯}{normalT}}_{sk}

) is required to be independent of thermal responses due to changes in

{\overset{true¯}{normalT}}_{sk}

, and is recognized as reliable information for evaluating the characteristics of body temperature regulation. Kakitsuba et al [6] demonstrated a seasonal difference in the CIZ as well as the effect of light intensity on the CIZ. The latter effect in particular indicates the possible incorporation of the non-visual pathway into the temperature regulation system.…”

Section: Introductionmentioning

confidence: 99%

The core interthreshold zone during exposure to red and blue light

Mekjavic

Katsuura

2013

J Physiol Anthropol

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BackgroundThis study tested the hypothesis that the core interthreshold zone (CIZ) changes during exposure to red or blue light via the non-visual pathway, because it is known that light intensity affects the central nervous system. We conducted a series of human experiments with 5 or 10 male subjects in each experiment.MethodsThe air temperature in the climatic chamber was maintained at 20 to 24°C. The subjects wore suits perfused with 25°C water at a rate of 600 cm3/min. They exercised on an ergometer at 50% of their maximum work rate for 10 to 15 minutes until sweating commenced, and then remained continuously seated without exercise until their oxygen uptake increased. The rectal temperature and skin temperatures at four sites were monitored using thermistors. The sweating rate was measured at the forehead with a sweat rate monitor. Oxygen uptake was monitored with a gas analyzer. The subjects were exposed to red or blue light at 500 lx and 1000 lx in both summer and winter.ResultsThe mean CIZs at 500 lx were 0.23 ± 0.16°C under red light and 0.20 ± 0.10°C under blue light in the summer, and 0.19 ± 0.20°C under red light and 0.26 ± 0.24°C under blue light in the winter. The CIZs at 1000 lx were 0.18 ± 0.14°C under red light and 0.15 ± 0.20°C under blue light in the summer, and 0.52 ± 0.18°C under red light and 0.71 ± 0.28°C under blue light in the winter. A significant difference (P <0.05) was observed in the CIZs between red and blue light at 1000 lx in the winter, and significant seasonal differences under red light (P <0.05) and blue light (P <0.01) were also observed at 1000 lx.ConclusionsThe present study demonstrated that dynamic changes in the physiological effects of colors of light on autonomic functions via the non-visual pathway may be associated with the temperature regulation system.