We review several physiological measurements for evaluation of human-environment systems, and discuss several relatively simple and useful methods focusing on those for evaluation of the autonomic and central nervous system. The methods used to evaluate the autonomic nervous system include blood pressure, electrodermal activity and electrogastrogram. In order to evaluate the central nervous system, we selected electroencephalogram, event-related potential and evoked potential. We demonstrate the examples of the studies which were conducted to evaluate the light environment, sound environment and mental work by using these parameters.

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In order to study the circadian rhythm of cognitive function related to auditory frequency system and melatonin secretion for people who preference to be active in the morning or at night, we have done an experiment at three time sessions. On the basis of a morningness/eveningness questionnaire, nine morning-type subjects (M-types) and ten evening-types subjects (E-types) were selected to participate in the present experiment. Diurnal changes of human cognitive function under 250/500 Hz and 1000/2000 Hz conditions were assessed hourly by auditory event-related brain potential using an oddball task. The melatonin rhythm was estimated by cosine-fitting curve of saliva melatonin concentration. Saliva samples (3–5 ml) were collected every hourly to determine peak salivary melatonin concentration before the measurement of P300. A marginally significant main effect of time of day (P=0.0512) and a significant main effect of stimulus frequency (P<0.05) in reaction time (RT) were found. There was a significant interaction between the circadian typology and time of day in RT (P<0.001). A significant main effect of circadian typology (P<0.001) and time of day (P<0.05) in P300 amplitude was found. The P300 amplitude between M-types and E-types was significantly different at 10:00, 11:00, 12:00, 21:00, 23:00, 24:00 and 01:00. A significant main effect of stimulus frequency in P300 amplitude was found (P<0.01). There was a significant interaction among the circadian typology, time of day and stimulus frequency in P300 amplitude (P<0.05). The P300 amplitude obtained after the low-frequency stimulus was significantly different than that obtained after the high-frequency stimulus at 10:00, 12:00, 19:00, 20:00, 23:00 and 24:00 for M-types, and at 12:00, 19:00, 21:00 and 01:00 for E-types (P<0.05). These findings suggest that the diurnal change of human cognitive function was related to different circadian typology, and may have important implications for industries employing different work shifts or workers using flexible working hours.

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It is well known that elevations in body temperature can impair both physical and cognitive performance. For helicopter pilots, the major heat source during flight originates from solar radiation. However, when nuclear, biological and chemical (NBC) protective clothing is worn, metabolic heat generated during the pre-flight period, and during the mission, is trapped, exacerbating thermal strain. In this project, the hypothesis that elevations in body heat content would degrade flight performance was tested. Six helicopter pilots completed three, two-hour flight simulations under three levels of thermal strain, administered in a balanced order. Thermal strain was induced using a water-perfusion garment, worn under flight and NBC clothing, and supplied with water that would elicit skin temperatures of 33°C (control), 37°C (moderate) and 39°C (hot). Each sortie was programmed and controlled by the simulator flight officer (blind to treatment order), and was comprised of eight flight circuits, each involving takeoff and landing exercises. During each circuit, the pilots were required to identify and solve two operational problems, graded as “easy”, “moderate” and “hard”. Terminal core temperatures for each trial were: 37.4°C (±0.13; control), 38.4°C (±0.16; moderate) and 38.8°C (±0.15; hot). This strain was also reflected within the terminal heart rates: 85.0 b.min⁻¹ (±5.2; control), 126.0 b.min⁻¹ (±5.0; moderate) and 147.3 b.min⁻¹ (±6.0; hot). The simulator officer independently graded pilot performance, and while the moderate trial resulted in slightly reduced performance scores, relative to control (P>0.05), scores were significantly lower in the hot trials (P<0.05). Strong correlations existed between the thermal load and both the effort needed to sustain the appropriate flight performance, and the pilots’ own assessment of performance quality. From these data, it appears that mean body temperature may be linked with perceived performance quality, whilst mean skin temperature appears to be linked with effort perception. In both instances, the explained variance exceeded 65%.

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It is important to understand the applicable conditions and characteristics of thermal indices for their proper application. In this paper, the characteristics of the required sweat rate of the previous ISO 7933 standard are investigated from the viewpoints of the thermal physiology and thermal equilibrium of the human body. A linear multiple regression formula used for the prediction of skin temperatures is not always consistent with the relation between the thermal physiological states and sweat secretion in the human body. With the decrease in the sweat efficiency brought about by hot and humid conditions, an error in the evaluation of skin temperature leads to a larger error in operative temperature according to the previous ISO 7933. In order to compensate for this error, this paper suggests that both the skin temperature and sweat rate should be evaluated based on the thermal equilibrium of the human body and the relationship between the thermoregulatory system and thermal physiological states. In order to create a new hot environmental index based on the previous ISO 7933 standard, which uses heat storage and dehydration as parameters for evaluation, the authors present an example of such evaluation methods. In this example, sweat secretion corresponds with the rise in skin temperature.

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Thermal sensation is influenced by both individual and environmental factors. However, it is unknown which individual factors are significant to determine thermal sensation of humans. The purpose of this study was to clarify the relationship between the thermal sensations, skin temperatures and individual factors such as exercise experiences by observational methods. 334 young examinees who entered Tokyo Metropolitan University in 2003 cooperated with these experiments during the classes of physical education. Interview and questionnaire on individual factors (gender, exercise experiences, climates in the past-to-present habitations and thermal sensation votes) of examinees, taking thermal infrared images of them and meteorological observations were conducted in the gymnasium of the university in the seven days. To evaluate the relationship with exercise experiences, obtained data were divided into 3 categories, i.e., (1) no exercise experiences in schools, (2) experiences until the end of junior high school, and (3) experiences until the end of high school or still getting exercise. The following results were obtained.

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It was proposed to calculate a formula for mean skin temperature weighted with both the heat transfer coefficient and skin surface area ratios. Calculating the mean skin temperature based on the heat balance equation between the human body and the environment yielded the formula with the weighting factor including not only the skin surface area ratio but also the heat transfer coefficient ratio. Local heat transfer coefficients in the weighting factor for calculating mean skin temperature were measured using a thermal manikin. New weighting factors were determined at seated and standing postures. The weighting factors were not influenced by either air velocity or the temperature difference between the skin surface and the air. Mean skin temperature calculated using the weighting factor of the present study was compared with that calculated using the weighting factor previously proposed.

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