Akinori Yasuda

Effects of partial sleep restriction and subsequent daytime napping on prolonged exertional heat strain

Objectives It is considered that sleep restriction is one of the risk factors for the development of exertional heat stroke and illness. However, how sleep restriction affects exertional heat strain and the nature of the coping strategy involved in this phenomenon remain unclear. Methods Fourteen healthy subjects were studied on four occasions: after a night of normal sleep (NS, 7–8 h) and after a night of partial sleep restriction (PSR, 4 h), each with or without taking a daytime nap during the subsequent experimental day. The laboratory test consisted of two 40 min periods of moderate walking in a hot room in the morning and the afternoon. Results The increase in rectal temperature during walking was significantly greater in PSR than in NS in the afternoon. The rating scores for physical and psychological fatigue and sleepiness were significantly greater in PSR than in NS, both in the morning and in the afternoon. The reaction times and lapses in the psychomotor vigilance task (PVT) after walking were significantly worse in PSR than in NS in the morning and after lunch. The nap intervention attenuated significantly the scores for fatigue and sleepiness in PSR. Furthermore, the decreased PVT response in PSR was significantly reversed by the nap. Conclusions These results suggest that PSR augments physiological and psychological strain and reduces vigilance in the heat. Taking a nap seemed to be effective in reducing psychological strain and inhibiting the decrease in vigilance.

Pre-cooling by hands and feet water immersion reduces heat strain while wearing protective clothing

Pre-cooling (i.e., removal of heat from the body immediately prior to exercise) is a popular strategy for improving exercise performance in hot conditions. Whole body immersion in water is the procedure most commonly used to pre-cool in sports activities. However, the supply of a large volume of water and ice in all occupational settings is not always possible, or practical. In the present study, we examined the effectiveness of hands and feet water immersion and cooling vest as practical pre-cooling method on heat strain while wearing protective clothing.

Examination of validity of a conditioned odor aversion (COA) procedure using low-dose of organic solvent as an applied procedure of the conditioned taste aversion

Smell of very low dose of chemical might evoke subjective physical symptoms in human by some process of learning named the aversion conditioning. But few scientific evidences of the hypothesis have been reported so far. Validity of conditioned odor aversion (COA) using low-doses of organic solvent as odor conditioned stimulus (CS) was examined. In conditioning phase, water-deprived male Sprague-Dawley rats were presented low, medium or high dose solution for 30 min followed by 0.3 M Lithium Chloride (LiCl) solution or saline injection. The xylene solution and drink water were simultaneously provided on the next day as two-bottle test. Consumption of medium dose of xylene solution was significantly decreased in LiCl injection group as compared with saline group. There was no difference between LiCl and saline injected animals in low group. Animals in high dose did not access to xylene even on the conditioning. These results indicate that animals showed high sensitivity for discrimination against concentration of xylene and that the medium dose of xylene functioned as the CS. We concluded that the COA used in the present study may be one of useful procedures to investigate olfaction of animal.

Physiological responses and balance ability are affected by physical workload and heat exposure in workers

Japan is experiencing high temperatures and relative humidity (rh) during the summer months, which lead to increases in the incidence of heat stroke among outdoor workers. According to the Ministry of Health, Labour and Welfare in Japan, between 2010 and 2012, approximately 86 deaths were caused by heat stroke, of which 40% occurred at construction sites [1]. This study aimed to determine whether physical performance, especially balance ability, deteriorates with increased physical workload and heat exposure. In addition, we aimed to determine the relationship of physiological responses and balance function with heat exposure.