14 ENERGY TRANSFORMATIONS DURING HORIZONTAL WALKING. 



From these data he concludes that the carbon-dioxide production of 

 a working man is not a function of his work, since the metabolism 

 decreases with practice. 



Observations of Katzenstein, 1891. In the walking experiments of 

 Smith and Gruber, only the carbon-dioxide production was deter- 

 mined, and the first investigations, in which the oxygen consumption 

 was also measured, were those carried out by Katzenstein 1 in Zuntz's 

 laboratory in Berlin. Employing the Zuntz mouthpiece and valves 

 for separating the inspired air from the expired air, Katzenstein 

 sampled and analyzed the expired air, the measurement of the total 

 amount of air expired being made with a gas-meter. There is consider- 

 able doubt as to the conditions of the experiments. In certain instances 

 it is specifically stated that the subjects were in the post-absorptive 

 state, i. 6., without food for 12 hours, but the general impression is given 

 that in the majority of instances the experiments were not made with 

 the subject in the post-absorptive condition. The rate of walking was 

 from 51 to 92 meters per minute. The criticism was subsequently 

 raised by Durig 2 that the treadmill was not completely level, there 

 being a slight elevation of somewhat less than 1 degree. To provide 

 a base-line for these observations, the metabolism of the subject was 

 measured while he stood quietly upon the treadmill. Observations 

 were likewise obtained with the subject in a lying position. The author 

 concludes that the oxygen consumption for the unit of effective work is 

 greater for small amounts of work than for large amounts, and that the 

 respiratory quotient during work remains essentially unaltered. The 

 computation of the values per horizontal kilogrammeter is given in 

 table 1, page 22. 



Observations of Sonden and Tiger stedt, 1895. The large respiration 

 chamber in Stockholm afforded sufficient space for experiments in 

 which the work of walking could be measured. 3 The carbon dioxide 

 alone was determined and with most of the experiments moderate 

 amounts of food were taken. The body-weight with clothing was 

 recorded before and after the experiment. The subjects walked 

 from 3,000 to 5,920 steps per hour without a load. As a base-line the 

 authors used a value found for three resting periods when the subject 

 was sitting, these periods being between periods of walking; large 

 differences are shown in the carbon-dioxide output per hour during the 

 resting periods. The energy per horizontal kilogrammeter, as com- 

 puted from the carbon-dioxide output during the walking experiments, 

 is given in table 1, page 22. 



Observations of Schumburg and Zuntz, 1896. In connection with a 

 series of experiments made in the Alps, Schumburg and Zuntz carried 



Katzenstein, Archiv f. d. ges. Physiol., 1891, 49, p. 330. 



2 Durig, Denkschrift. d. math.-natur. Masse d. kaiserl. Akad. d. Wissensch., 1909, 85, p. 250. 



3 Sonden and Tigerstedt, Skand. Archiv f. Physiol., 1895, 8, p. 1. 



