Makoto Mayuzumi

Comparative studies on physical characteristics and resting metabolism between young male highlanders of Papua New Guinea and young male Japanese

Anthropometric measurements and measurements of resting metabolism were made on 15 young male highlanders in Beha village at altitudes between 1,500 m and 1,800 m in the Eastern Highland of Papua New Guinea in August in 1978 and 10 young male Japanese in Nishinomiya in September. New Guineans showed significantly lower height, considerably lower body weight than Japanese but heavier body weight for height and significantly greater mean values of Rohrers index and Brugschs index than Japanese. Skinfold thicknesses for New Guineans were significantly smaller than those for Japanese. Thus, physically, New Guineans were more muscular and athletic when compared with Japanese. The mean value of resting metabolic rate for New Guineans, 46.35 W/m2, at 25°C was considerably lower than that for Japanese, 51.01 W/m2. New Guineans showed significantly lower mean value of resting metabolism 47.57 W/m2 at 30°C than Japanese 55.16 W/m2. The mean values of respiratory quotient for New Guineans (RQ = 0.950 at 25°C and 0.971 at 30°C) were significantly greater than those for Japanese (0.81 at 25°C and 0.81 at 30°C). New Guineans showed considerably lower mean value of heart rate at 30°C (71.1 beats/min) than Japanese (79.2 beats/min). The smaller physique of New Guineans might be the result of lower caloric intake and protein intake as well as of living in a tropical climate.

COMPARISON OF SWEATING REACTIONS BETWEEN SUBTROPICAL AND TEMPERATE NATIVES

Publisher Summary This chapter presents a comparison of sweating reactions between subtropical and temperate natives. It is known that unacclimatized individuals sweat more readily and more profusely and that the sodium concentration in sweat decreases after repeated heat exposure in short-term heat acclimatization. These adaptative changes in sweating reaction observed during short-term heat acclimatization gradually disappear after cessation of heat exposure. The adaptive changes induced by short-term heat acclimatization in sweat reaction disappear within several weeks after cessation of heat exposure. On the contrary, fully acclimatized individuals sweat more slowly and less than unacclimatized subjects, and their sweating reaction is affected less by a change in ambient temperature. The cooling power of sweat is dependent on the degree of wetness of the skin and the difference between vapor pressure on the skin surface and that in the surrounding air.

Effects of different ambient temperatures on physiological responses during exercise and recovery with special reference to energy requirement

Observation of the physiological responses was made on seven young male subjects ages 27–31, during pedalling a bicycle ergometer at the constant work load of 600 kg. m/min for 20 min and recovery in 35°C with 50% RH, in 30°C with 50% RH and in 23°C with 50% RH. Heart rate, respiratory volume, total oxygen intake and energy requirement were increased with an increase in ambient temperature, while blood pressures were lower in a hot environment than in cooler environments. In 35°C, oxygen intake during exercise, oxygen debt and anaerobic fraction of oxygen debt had increased when compared with those in 23°C. Thus it is inferred that the energy requirement, the oxygen debt and the anaerobic fraction of the oxygen debt for a fixed work had increased more in a hot environment than in a comfortable environment. Factors which caused differences in the physiological reactions during exercise and recovery in different conditions are discussed.