254 Metabolism of Healthy Man. 



As the result of experiments on 55 men, with an average body-weight of 64.5 

 kilograms, awake and sitting quietly in a chair, it was found that the average 

 carbon-dioxide exhalation amounted to 33 grams per hour, the oxygen absorption 

 27 grams, and the heat production 97 calories. With 17 different men asleep with 

 an average body-weight of 66.6 kilograms, the average carbon-dioxide exhalation 

 was 23 grams, oxygen absorption 21 grams, and the heat production 71 calories. 

 Using the factors for the percentage increase in the metabolism due to the mus- 

 cular exercise of standing and for very severe muscular work, the values as given 

 in table 107 show that during very severe muscular work the carbon-dioxide ex- 

 halation may amount to 248 grams per hour, the oxygen absorption to 213 grams 

 and the heat production to 653 calories. As a matter of fact a series of experi- 

 ments made with a professional athlete showed that as much as 625 calories were 

 actually measured. 



In an earlier publication * it was pointed out that if values were known for 

 the approximate metabolism of varying conditions of muscular activity, one 

 could compute with reasonable accuracy the total metabolism for the day, and 

 in this earlier publication attempts were made to designate the various kinds of 

 muscular work as light, moderate, severe, and very severe. The futility of thus 

 attempting to indicate a degree of muscular activity by these adjectives has 

 been seen and no attempt will here be made to do this. We believe that the 

 results presented in table 107 for the metabolism during standing are reason- 

 ably accurate and can be used in such computations, and we believe, further- 

 more, that the metabolism during very severe muscular work indicates the 

 metabolism under conditions where the work was almost to the limit of human 

 endurance and strength. These two points are reasonably well fixed. It is to 

 be hoped that subsequent experiments will supply the missing data with special 

 reference to the energy requirement during walking. Until these factors have 

 been determined it will be practically impossible to compute the total energy 

 transformation of man during ordinary daily activity. 



On the other hand, the values here given for sleep and for sitting in a chair 

 will be of some service, it is hoped, in calculating the energy transformation of 

 convalescents and of bedridden patients. At present too little knowledge is 

 available with regard to the metabolism during recovery from a severe drain 

 upon body-material to predict accurately the metabolism. Thus it was found 

 that the recovery following a fast " resulted in a very noticeable storage of body- 

 material, nitrogen, and fat, although the question is as yet unsettled as to 

 whether the nitrogenous material stored under such conditions becomes active 

 protoplasmic tissue with the highest degree of metabolic activity. The question 

 can only be solved by an extensive series of experiments in which the nature of 

 the stored material can be studied from many standpoints. 



1 Atwater and Benedict, U. S. Dept. Agr., Yearbook 1904, p. 205. 



2 Benedict, Carnegie Institution of Washington Publication No. 77, 1907. 



