30 ENERGY TRANSFORMATIONS DURING HORIZONTAL WALKING. 



which it was shown that it was capable of measuring the metabolism 

 with an oxygen consumption as high as 3 liters per minute. 1 Careful 

 control tests of the apparatus have proved conclusively that, so far as the 

 mechanical construction is concerned, the measurement of the carbon- 

 dioxide production and the oxygen consumption is accurate. 



As a part of the plan for studying the metabolism during the various 

 phases of muscular work, a special type of treadmill was devised and 

 constructed in this laboratory several years previous to the present 

 research. Certain features of this treadmill, which will be described 

 subsequently, make it especially applicable for use in experiments with 

 men. Having, therefore, an exceptionally satisfactory treadmill and 

 a respiration apparatus capable of measuring the metabolism incidental 

 to severe muscular work, it was possible, in 1913-14, to make a study 

 of the metabolism of a subject while he was walking on a level. 



As soon as the respiration calorimeter for muscular work is ready for 

 use, the treadmill will be placed inside this apparatus and certain of 

 the experiments repeated. The indirect calorimetry computed from 

 the gaseous exchange as measured by the respiration apparatus can 

 thus be controlled by direct determinations of the energy output. 

 This control is of particular importance, since the use of any form of 

 respiration appliance, such as a mouthpiece or nosepieces, is open to 

 legitimate criticism in that the use of such artificial methods of breath- 

 ing, particularly with a very great ventilation of the lungs, may lead to 

 a disturbance in the mechanics of ventilation, thus causing a distur- 

 bance in the respiratory exchange. Although the universal respiration 

 apparatus has been carefully controlled as to the measurement of both 

 carbon dioxide and oxygen, nevertheless if there is a disturbance in the 

 mechanics of ventilation, as, for instance, an over-ventilation of the 

 lungs, there may be a considerable amount of carbon dioxide exhaled 

 that was not simultaneously produced. The retention of carbon 

 dioxide by altered respiratory mechanics is also not improbable. By 

 means of the studies with the respiration calorimeter, therefore, it will 

 be possible not only to determine the metabolism by direct calorimetry, 

 but also to obtain the gaseous exchange with free breathing without 

 the use of either mouth or nose appliance. 



It should furthermore be borne in mind that while the method of 

 computing the calorimetry from the gaseous exchange has, according 

 to our experience up to the present time, given highly satisfactory 

 results with muscular repose, there is always the possibility of a dis- 

 turbance in the character of the metabolism during severe muscular 

 work and a consequent disturbance in the relationship between the 

 gaseous exchange and total heat production. It is thus seen that the 

 final tests with the respiration calorimeter are essential for a complete 

 understanding of this problem. On the other hand, the previous 



Benedict and Cathcart, Carnegie Inst. Wash. Pub. No. 187, 1913. 



