[Gas exchange and physical work capacity of natives of different geographical regions]

A study was carried out to investigate exercise tolerance, gas exchange and external respiration of Latin-American students who lived in Moscow for a year. As controls Soviet students residing in and around Moscow were used. The above parameters were measured at a different time of the day in response to a hypercapnic exposure. Exercise tolerance was determined using the test PWC170. External respiration and gas exchange were investigated at rest and during 5 min exercises with a load of 1 and 2 Wt/kg body weight. CO2 sensitivity was determined by means of the rebreathing method. In the evening the Latin-American students showed a trend towards an increase of the cardiorespiratory activity and exercise tolerance. The Soviet students did not display changes in exercise tolerance. The Latin-American students showed an increase in the morning and a decrease in the evening of external respiration reactions. The Soviet students exhibited opposite variations. Direct alveolar measurements demonstrated an increase of pCO2 in the alveolar air in the Latin-American students in the evening and a decrease of the parameter in the Soviet students. It is suggested that cyclic changes in external respiration in response to hypercapnia are associated with exercise tolerance.