NUTRITION INVESTIGATIONS AND THEIR RESULTS. 369 



the respiration calorimeter the desired data may be calculated approx- 

 imately. In the experiments referred to all grades of muscular 

 activity have been tested, from the quiet of a fasting subject in deep 

 sleep to the excessive muscular work of a professional bicycle rider 

 whose powers were taxed to the utmost. When muscular work was 

 performed other than that involved ui the ordinary motions essential 

 to eating and drinking and moving about in the respiration chamber, 

 the muscular exercise consisted in operating a bicycle-like apparatus. 

 The ease with which the wheel turned, and hence the severity of the 

 work could be regulated, and the total amount of work performed 

 could be accuratel}'' measured. 



It Avill be remembered that in discussions of body energy the amount 

 of work is measured in terms of heat, the calorie being the commonly 

 accepted heat unit. It should also be said that under usual conditions 

 the total heat output during a given period affords an indication of 

 the muscular activity of the body. When the body is quiet the heat 

 output is small and when it is active the heat output is correspond- 

 ingly larger, and the same is true of the carbon dioxid output. The 

 average results of the experiments showing the output of carbon 

 dioxid and heat for the body under the different conditions indicated 

 are summarized in the table following, and with the aid of such data 

 the total carbon dioxid and heat output, and hence the total energy 

 output of the body, may be calculated. 



Average normal output of carbon dioxid and heat from the body. 



Conditions of muscular activity. 



Man at rest, sleeping 



Man at rest, awake, sitting up 



Man at light muscular exercise 



Man at moderately active muscular exercise. 



Man at severe muscular exercise 



Man at very severe muscular exercise 



Average quantities 

 per hour. 



Carbon 

 dioxid. 



Grams. 



25 



35 



55 



100 



150 



210 



Heat. 



Calories. 

 65 

 100 

 170 

 290 

 450 

 600 



It will be seen that the output not only of heat but also of carbon 

 dioxid is very nearly proportional to the amount of muscular work. 

 As an example of the way in which the data included in the table may 

 be used for calculating the carbon dioxid and heat output under 

 varying degrees of muscular activity the following may be cited: 



If a man sleeps eight hours . per day, we may say that the carbon 

 dioxid output during this period is approximately eight times the 

 hourly amount eliminated during sleep by the average subject, or 

 8 by 25 = 200. If he is at very severe muscular labor for eight hours, 

 the carbon dioxid output would correspond to eight times the hourly 

 amount for very severe work, that is, 8 by 210 = 1,680. And if the 



294b— 07 24 



