SECTIONAL ADDRESSES. 
ft 
Gn 
(o/) 
Running and Swimming: Shorter Times. 
In fig. 1 all the important world’s records are presented, average speed 
against time, for men and women running and for men and women swim- 
ming. The crosses representing men rowing in an 8-oar boat will be dis- 
cussed later. It is obvious in all four cases that we are dealing with the 
same phenomena, a very high speed maintainable for short times, a speed 
rapidly decreasing as the time is increased and attaining practically 
a constant value after about 12 minutes. There are no reliable records, 
in the case of swimming, for times of less than about 50 seconds, so that the 
curves cannot be continued back as far as those for running. There can, 
however, be no doubt that the curves for running and swimming are essen- 
tially similar to one another and must depend upon the same factors. 
In running, starting inertia is the cause of the initial upward trend of the 
curves: a maximum average velocity is attained in the case of men for 
about 200 yards, of women for about 100 yards; after that a rapid 
decrease sets in, ending only when the time has become 10 or 15 minutes, 
the distance two to three miles. The phenomena shown in fig. 1 are 
susceptible of a fairly exact discussion. 
Oxygen Intake, Oxygen Requirement, and Oxygen Debt. 
In recent papers my colleagues and I have tried to emphasise the 
importance of a clear distinction between the oxygen intake and the 
oxygen requirement of any given type and speed of muscular effort. 
When exercise commences, the oxygen intake rises from a low value 
characteristic of rest to a high value characteristic of the effort undertaken. 
This rise occupies a period of about two minutes; it is nearly complete 
in 90 seconds. The oxygen used by the body is a measure of the amount 
of energy expended: one litre of oxygen consumed means about five 
calories of energy liberated, enough to warm 5 litres of water one degree 
centigrade—expressed in mechanical energy, enough to raise about one ton 
seven feet into the air. It has been established, however, that the oxygen 
need not necessarily be used during the exertion itself. The muscles have 
a mechanism, depending upon the formation of lactic acid in them, by 
which a large amount of the oxidation may be put off to a time after the 
exercise has ended. The recovery process, so called, is a sign of this 
delayed oxidation : it is just as important to the muscle as recharging to 
an electrical accumulator. The degree, however, to which the body is able 
to run into debt for oxygen, tocarry on not on present but on future 
supplies, is limited. When an oxygen debt of about 15 litres has been 
incurred the body becomes incapable of further effort: it is completely 
fatigued. In anything but the shortest races our record-breaking athlete 
should finish with something near a maximum oxygen debt, otherwise 
he has not employed all his available power, he has not done himself 
full justice. The maximum effort, therefore, which he can exert over a 
given interval depends upon the amount of energy available for him, 
upon (a) his maximum oxygen intake (that is, his income) and (6) his 
maximum oxygen debt (that is, the degree to which he is able to overdraw 
his account). These maxima are fairly well established for the case of. 
athletic men of average size—about 4 litres per minute for the one, about 
15 litres for the other. 
a i tie 
