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Biomedical subjects

H Ihzuka

Publications and source records attributed to H Ihzuka.

5 recordsLinked to original sources
PubMed1979

Studies on heat tolerance at rest and orthostatic heat tolerance in a hot environment.

Twelve young male Japanese were exposed to a hot environment in summer, and changes in systolic blood pressure induced by changing the position from recumbent to sitting were observed. Sweating was induced in a climatic chamber at 30 degree C with 70% relative humidity by immersing both legs up to the knees into a water bath of 42 degree C for 90 min after sitting on a chair at rest for 30 min in the chamber. The mean values of rise in rectal temperature, body weight loss and mean sodium concentration in sweat were 0.62 degree C, 0.67 kg and 46 mEq/l, respectively. The mean values of fall in systolic blood pressure associated with changing posture and its recovery time were 13.7 mm Hg and 77.5 sec, respectively. Heat tolerance at rest was assessed by a numerical heat tolerance index involving relative water loss, relative rise in rectal temperature, and relative salt loss. Values of relative water loss, relative rise in rectal temperature, and the numerical heat tolerance index correlated closely to those of fall in systolic blood pressure and its recovery time.

Adult↗
PubMed1979

Correlation between heat tolerance during exercise and maximum aerobic work capacity.

Observation of the physiological responses during exercise in a hot environment and measurement of maximal work capacity were made on eight young male subjects, ages 20--22. Exercise was performed on a bicycle ergometer at a constant work load of 450 kg . m/min at a cycling rate of 50 rpm for 30 min in a climatic chamber at 30 degree C with 70% relative humidity. The maximum work capacity was measured by bicycle ergometer exercise. Heat tolerance during exercise was assessed by the magnitude of physiological strain expressed by the combination of relative rise in rectal temperature, relative water loss and relative salt loss. Heat load during exercise was calculated using metabolic rates at rest and during exercise, assuming heat loss through the respiratory tract to be 10 percent of metabolic rate. Fairly good correlations were found between the ratio of work done to maximum work capacity and rise in rectal temperature, ratio of body weight loss to body weight and heat tolerance during exercise. Close correlations were found among relative heat load during exercise and rise in rectal temperature, relative body weight loss and heat tolerance. Heat tolerance during exercise in a hot environment correlated well to capacity of heat dissipation and maximum work capacity.

Adult↗
PubMed1976

Studies on physiological responses of residents in Okinawa to a hot environment.

In an attempt to reconfirm Kuno's observation that changes in sweating reaction during long-term heat acclimatization differ from those during short-term heat acclimatization, Ohara's sweating test was performed in summer in Okinawa on 37 male subjects, including 19 residents born and raised in Okinawa (group O) and 18 residents born and raised on one of the main Japanese islands (group M). Seasonal variation of adaptability to heat was also studied in some subjects of both groups. Group O showed significantly less sweat loss, lower Na concentration in sweat and a longer latent period for onset of sweating than group M. Group O showed no seasonal variation in sweat loss, while group M showed considerably greater sweat loss in summer than in winter. In both groups, lower Na concentration in sweat, lower rise in rectal temperature and lesser increase in heart rate in summer than in winter were observed. Seasonal difference in physiological responses of group O to heat exposure was less than that of group M. In conclusion, it was assumed that acclimatization to heat of group O had advanced further than that of group M and this was the reason for longer latent period of sweating and lesser sweat loss in group O in spite of the same rise in rectal temperature in both groups. Discussions were carried out to explain how the sweating pattern and mechanism of acclimatization in group O were different from those in group M.

Acclimatization↗