Some physiological responses of man to workload and environment

¹ North Carolina State College, Raleigh, North Carolina

The heart rate, ventilation rate, oxygen consumption rate, and mechanical efficiency responses of a subject to a series of temperatures, relative humidities, and workloads were observed. A quadratic prediction equation of each of the responses as steady-state functions of the independent variables was derived. Each of the equations represents a four-dimensional hypersurface. For the heart rate, ventilation rate, and oxygen consumption rate the hypersurfaces are quite similar, the responses increasing rapidly with respect to workload and about one-third as rapidly with respect to temperature. The effect of relative humidity was present primarily as interactions. Mechanical efficiency was represented by a more complex hypersurface. In three dimensions, with relative humidity as a parameter, the response was a saddle-shaped surface with the highest efficiency at a condition of low temperature, high workload. At constant environment, the heart rate responses of 19 subjects to workloads was observed and found to be linear with a normal distribution of slopes.