I.— PHYSIOLOGY. 161 
a maximum oxygen debt of 15 litres, a maximum oxygen intake of 3°5 litres 
per ininute, and the supposition that at the end of the race the performer 
is completely exhausted. A similar calculated curve is given for the case 
of running, on the hypothesis of a maximum oxygen debt of 15 litres and 
20 
15 
PER MINUTE 
10 
CALCULATED OXYGEN REeQuiIRENENT 
LITRES 
SPEED: Swinnying . YARDS PER ny 
14 I-6 ‘8 
2 9, 
7 8 
SPEED: RUNNING: YARDS. PER SEC. 
Fie. 3.—Oxygen requirement, running and swimming, of record-breaking athletes, 
calculated from curves of fig. 1, on the assumption that at the end of a race the per- 
former is completely exhausted, having attained his maximum oxygen debt. Maximum 
oxygen debt assumed=15 litres for both. Maximum oxygen intake assumed : for 
running=4 litres per minute; swimming=3.5 litres per minute. Method of cal- 
culation described in the text. 
a maximum oxygen intake of 4 litres per minute. These curves are 
similar in character to those shown in fig. 2 for the cases of running 
and standing-running, which have been investigated in the laboratory. 
There can be little doubt that the factors here described are the chief 
“agents in determining the form of the curves given in fig. 1. 
Limits of the Argument. 
It is obvious that we must not pursue the argument too far. A man 
cannot exhaust himself completely in a 100 or a 200 yards race: even 300 
yards is not sufficient to cause an extreme degree of exhaustion, though a 
quarter-mile, in the case of a first-class sprinter, is enough, or almost 
enough, to produce complete inability to make any immediate further 
s effort. We have found an oxygen debt of 10 litres even after a quarter- 
mile in 55 seconds. It is obvious, therefore, that we cannot pursue our 
argument below times of about 50 seconds, that the maximum speed is 
limited by quite other factors than the amount of energy available. It 
is not possible in any way to release energy explosively for very short 
intervals of effort: other factors determine the maximum speed, factors 
1925 M 
