14 MUSCULAR WORK 
Smith also studied the carbon dioxide expired during work on a treadmill 
having 43 steps, ascending 28.65 feet per minute, the carbon dioxide being 
determined for short periods of a few minutes each. The after-effect of the 
muscular work is excellently shown by the fact that the pulse-rate during 
Smith's work experiment of October 9 was 150, and after 29 minutes of rest 
it was 102 beats per minute, while his pulse-rate in a period of rest was as a 
rule considerably under 88; furthermore, even after 29 minutes of rest, 9.14 
grains of carbon dioxide were given off per minute as compared with approxi- 
mately 6 grains during rest before work. 
Using the large respiration chamber at Munich, Pettenkofer and Voit a 
made a number of experiments on men at rest and with muscular work. 
For a subject they employed a man who had been accustomed to using a 
foot-power lathe, and the resistance of the apparatus was so adjusted as to 
correspond to his daily work. The man worked 9 hours each day. The work- 
periods were compared not only with ordinary rest-periods, but with rest- 
periods in which the subject fasted. Thus, in a series of three 24-hour fasting 
experiments, the subject gave off during the first two days of rest 738 and 695 
grams of carbon dioxide respectively, while on the third day, which was a 
work-day, he gave off 1,187 grams. In another series, in which the work 
followed rest with food, the results for the first three days of rest were 912, 
943, and 930 grams of carbon dioxide respectively, while those for the two 
working-days were 1,285 and 1,134 grams of carbon dioxide respectively. 
The apparatus used did not permit direct measurements of oxygen, and 
although the investigators computed the oxygen consumption, their com- 
putations were subsequently shown by Voit to contain errors. 
In 1881 Voit b reported two other experiments in which the subject 
worked without food, but no statement as to the method by which the work 
was performed was given. In the first experiment the work lasted 5 hours, 
corresponding to 29,529 kilogrammeters per hour. According to Voit, this 
called for an increase in the metabolism of 9.1 grams of fat per hour. A 
second man weighing 60 kilograms, likewise without food and working under 
exactly the same conditions, performed in an hour 19,036 kilogrammeters of 
work, requiring an increased decomposition of 7.2 grams of fat. Averaging 
the results of these two experiments, Voit computed that a load or task 
necessitating 24,282 kilogrammeters of ; work in an hour resulted in an 
increased decomposition of 8.2 grams of fat, this being equivalent to a 
production of 23.0 grams of carbon dioxide. 
As early as 1866 Speck," employing a new design of respiration apparatus 
in which the expired air was collected in a spirometer and then analyzed, made 
a number of experiments with muscular work. In these experiments, which 
lasted from 6 to 9 minutes, both the carbon-dioxide production and the oxygen 
consumption were determined. The muscular work consisted in raising a 
weight by the bent arm to a given distance, the weight and height being used 
for the computation of the amount of work performed in kilogrammeters. 
In 1871 a second series of experiments was made in which the weight was 
raised as before, but was lowered by an assistant. The experimental periods 
averaged about 4 minutes. 
a Pettenkofer and Voit, Zeitschr. f. Biol., 1866, 2, p. 459. 
6 Voit, Hermann's Handbuch der Physiologie, Leipsic, 1881, 6, part I, p. 202. 
c Speck, Physiologie des menschlichen Athmen3, Leipsic, 1892. 
