The effects of bright light exposure during the daytime on circadian urinary melatonin and salivary immunoglobulin A (IgA) rhythms were investigated in an environmental chamber controlled at a global temperature of 27 degrees C+/-0.2 degrees C and a relative humidity of 60%+/-5%. Seven diurnally active healthy females were studied twice, in bright and dim light conditions. Bright light of 5000 lux was provided by placing fluorescent lamps about 1 meter in front of the subjects during the daytime exposure (06:30-19:30) from 06:30 on day 1 to 10:30 on day 3. Dim light was controlled at 200 lux, and the subjects were allowed to sleep from 22:30 to 06:30 under both light exposure conditions. Urine and saliva were collected at 4h intervals for assessing melatonin and IgA. Melatonin excretion in the urine was significantly greater during the nighttime (i.e., at 06:30 on day 1 and at 02:30 on day 2) after the bright light condition than during the dim light condition. Furthermore, the concentration and the amount of salivary IgA tended to be higher in the bright light than in the dim light condition, especially during the night-time. Also, salivary IgA concentration and the total amount secreted in the saliva were significantly positively correlated with urinary melatonin. These results are consistent with the hypothesis that bright light exposure during the daytime enhances the nocturnal melatonin increase and activates the mucosal immune response.

Following the previous studies on the influence of light with different wavelengths on human biological rhythms during nighttime, present experiments were conducted to investigate the influence of morning light on the behavior of the core temperature and melatonin in humans. The experiments were carried out in four subjects with normal color vision. The subjects were exposed between 4:00 h to 9:00 h to red, green and blue light of 1,000 lux and 2,500 lux, and with an incandescent light of 50 lux as control. The main results were as follows: No differences in the behavior of core temperature and melatonin were found under the influences of red, green and blue light of 1,000 lux and the control light of 50 lux. On the other hand, a tendency to promote the increase of core temperature and the fall of melatonin secretion was found after exposure to green light of 2,500 lux, compared with control and red light. These results indicate that the behavior of core temperature and melatonin differs according to the wavelength of light, and that the phenomenon arises with morning as well as nocturnal irradiation. However, the intensity of light required to bring about the phenomenon seems to be different between morning and evening; an irradiation of 1,000 lux x 5h at night in the previous report, and one of 2,500 lux x 5h in the morning in the present experiments, were found to be necessary for green light to cause the effects.

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This study investigated the effects of three different types of clothing on the circadian rhythms of core temperature and urinary catecholamines. One type of clothing consisted of long-sleeved shirts, full-length trousers, and socks (Type L, 1,042 g); the second type was of half-sleeved shirts and knee-length trousers (Type H, 747 g); the third type was of Type H during the daytime and Type L during night sleep (Type M). Six healthy females participated in this study where rectal temperature, skin temperatures, heart rate, and urinary catecholamines were continuously measured for 37.5 h at an ambient temperature of 23.8 +/- 0.2 degrees C and a relative humidity of 60 +/- 5%. The results were as follows: (1) The nocturnal minimum of rectal temperature decreased significantly in the sequence Type L < Type M < Type H clothing, and 27.2 and 12.4% of the circadian amplitude were influenced by type of clothing during the daytime and the nighttime, respectively. (2) The rise of skin temperatures in the extremities increased significantly more after the subjects retired for sleep with Type M or Type H clothing than with Type L. (3) Urinary catecholamines decreased more in the evening and increased more in the morning with Type H and Type M clothing than with Type L. These results show that the circadian rhythm of core temperature, especially the nocturnal minimum value, was influenced by the type of clothing worn not only during the nighttime, but also during the daytime.

Hyperthermia is considered to be one of the most important factors limiting human physical performance [1][2][3][4][5][6][7][8][9]. González-Alonso et al. [3] showed that high internal body temperature caused fatigue in the trained subjects during prolonged exercise in uncomfortable hot environments and time to exhaustion in hot environments was inversely related to the initial internal body temperature. Edward et al. [2] have demonstrated that the heating of the leg resulted in a marked reduction of endurance time during repeated isometric contractions in comparison with that achieved when muscle temperature was lowered. Furthermore, Olschewski and Brück [8] found that an increase in endurance time after precooling was accompanied by several muscular, cardiovascular and thermoregulatory advantages. Furthermore, Zhang and Tokura [10] found that the mean number of contractions during handgrip exercise with a hand ergometer was significantly higher after prior exposure to bright light (5000 lux) than to dim light (50 lux), and hypothesized that the prolonged duration of handgrip exercise arises because of reduced setpoint of core temperature. Therefore, fatigue in heat stress conditions might be related to higher core and active muscle temperatures, which affects the exercise performance. 1 In addition, human thermophysiological responses during exercise were greatly influenced by kinds of clothing [11][12][13][14][15][16][17][18][19][20]. Many investigators have found that hydrophilic textiles such as cotton and wool seem to have beneficial influences on thermal physiological response as well as overall comfortAbstract The purpose of this study was to investigate the effects of the hygroscopic properties of clothing material on pitching speed and some physiological responses in amateur baseball players. The experiments were performed on four male players of a regular high school baseball team and comprised two clothing types with different moisture absorption properties, namely, cotton (Type C) and polyester and polypropylene (Type P). One test session was conducted with seven innings, with a 5-minute rest time between each inning. During each inning the test subject pitched 20 balls with a 20-second interval between each pitch. From the results, in the hot environments, the trained baseball players tended to pitch balls with higher speed and less deviation of speed when wearing Type C clothing, especially in the second session. Type C clothing with a higher moisture regain compared to Type P clothing may have diminished accumulated thermal induced fatigue in the subjects.