Abstract
Experimental data further defining the region of predominant respiratory stress is presented. Within this region, energy requirements of respiration increase disproportionately to the overall energy expenditure of the body as exercise intensity increases. Addition of a mask accentuates this tendency, especially since no physiological compensation is possible in mask parameters. Mask technology has improved masks to the point where they no longer dominate the man-mask system, but instead contribute resistances and dead volumes approximately equal to those naturally occurring in man. Modeling base on minimization of respiratory energy rate of expenditure in the human is applied to this man-mask system and predictions are made which to this point have been nearly impossible to obtain from experimental data.