Combined influences of ambient temperature and graded work on cardiopulmonary functions

Several cardiopulmonary items were measured in eight adult females who had performed stationary ergometer cycling of 75-450 kgm/min in air temperature between 14 degrees and 35 degreesC. The experiments were designed on the basis of the Latin square method and the results were analyzed by computing the analysis of variance and multiple regression equations for each item linked with work rate and air temperature. In view of the degree of affinity of the effect of work rate and that of air temperature, the items could be divided into three groups. The first group consisted of items of pulmonary functions closely related with work rate but independent of air temperature, such as pulmonary ventilation, oxygen intake, carbon dioxide production, respiratory exchange ratio, and ratio of oxygen removal. The second group characterized by linear dependency on air temperature included mean skin temperature and mean innermost air temperature. The third group consisting of heart rate, pulse sum during work, and work pulse sum was intermediate. In spite of the confusion in the literature about the attitude of oxygen intake or mean skin temperature during work in heat, the former was the most stable in relation to change in air temperature and the latter was independent of work intensity.