46 ENERGY TRANSFORMATIONS DURING HORIZONTAL WALKING. 



WALKING AND RUNNING EXPERIMENTS. 



In the walking and running experiments the routine was essentially 

 that previously outlined for the standing experiments, save that during 

 the entire period and for several minutes before the experiment began 

 the subject was walking upon an electrically driven treadmill which 

 was kept in motion at a definite rate of speed. These rates of speed 

 varied from 53 meters per minute to 149 meters per minute. The 

 flexibility of the mouthpiece and its attendant by-pass made it possible 

 for the subject to walk with perfect comfort at these varying speeds and 

 the vertical movement of the body with each step did not interfere in 

 the slightest with the correct measurement of the gaseous exchange. 

 With a slow speed, there was no noticeable extraneous muscular effort 

 other than that of walking; with a high speed the subject made vig- 

 orous lateral motions of the arms, as is quite common with profes- 

 sional pedestrians when walking at high speed. As previously noted, 

 an attempt was made to measure the influence of this lateral motion by 

 studying the metabolism with the subject standing and swinging the 

 arms. In a number of the experiments the subject ran, although the 

 rate of progression was but little higher than in the experiments with 

 fast walking. 



EXPERIMENTS WITH FOOD. 



A considerable number of experiments were made after a breakfast 

 selected by the subject; a few were also made after dinner, the diet being 

 uncontrolled. In the experiments in which a study was made of the 

 possible influence of diets containing a preponderance of protein, fat, or 

 carbohydrate, the first meal of the day was given to the subject at the 

 Laboratory after a walking experiment in the forenoon in which he 

 was in the post-absorptive state. This meal consisted of steak, rice, 

 potatoes, or various fats. A second walking experiment was then made 

 under otherwise identical conditions. The exact weight of food was 

 not recorded, since our only aim was to make sure that the body was 

 plentifully supplied with the special food constituent being studied. 

 In general, the subject ate all that he possibly could and as a con- 

 sequence was frequently disinclined to walk in the afternoon. 



A careful study of the effect of muscular work upon the urine was 

 impracticable, hence no analyses of the urine accompany these observa- 

 tions. Previous tests with one of the subjects have shown, however, 

 that the accomplishment of a large amount of severe muscular work was 

 not accompanied by an excessive excretion of nitrogenous products in 

 the urine. 1 



'Benedict and Cathcart, Carnegie Inst. Wash. Pub. 187, 1913, p. 98. 



