168 SECTIONAL ADDRESSES. 
Long-distance Records. 
In fig. 1 we saw that the speed fell to what seemed to be practically 
a constant level towards the right of the diagram : this fall represents the 
initial factor in fatigue. On the logarithmic scale, however, where the 
longer times are compressed together, the curve continues to fall through- 
out its length. This later fall is due to factors quite different from those 
discussed above. Consideration merely of oxygen intake and oxygen debt 
will not suffice to explain the continued fall of the curve. Actually the 
curve beyond 10 miles seems to some degree doubtful. Apparently 
the same extent of effort has not been lavished on the longer records : 
the greatest athletes have confined themselves to distances not greater 
than 10 miles. The curve A drawn through all the points has a suspicious 
downward bend in it, which suggests that if Alfred Shrubb or Nurmi had 
tried to break the longer records they would have done so very effectively. 
Possibly the true curve lies more like the continuation ©: possibly it 
may be intermediate as shown at B. It would seem doubtful, indeed, 
whether the running curve and the walking curve are really to meet 
at about 150 miles. The most probable continuation of the running curve 
would seem to be somewhere between the lines B and C. 
The continued fall in the curve, as the effort is prolonged, is probably 
due to the second and third types of fatigue which we discussed above, 
either to the exhaustion of the material of the muscle, or to the incidental 
disturbances which may make a man stop before his muscular system 
has reached its limit. A man of average size running in a race must expend 
about 300 gms. of glycogen per hour; perhaps a half of this may be replaced 
by its equivalent of fat. After a very few hours, therefore, the whole 
glycogen supply of his body will be exhausted. The body, however, 
does not readily use fat alone as a source of energy: disturbances may 
arise in the metabolism ; it will be necessary to feed a man with carbo- 
hydrate as the effort continues. Such feeding will be followed by digestion ; 
disturbances of digestion may occur—other reactions may ensue. For 
very long distances the case is far more complex than for the shorter 
ones, and although, no doubt, the physiological principles can be 
ascertained, we do not know enough about them yet to be able further to 
analyse the curves. 
Women’s Running Records. 
The women’s curve, as far as it goes, is very similar to the men’s. 
Some records again are better than others. An enterprising woman 
athlete who wants to break a record should avoid the 300 metres; she 
would be well advised to try the 500 metres. It would be very interesting 
to have an intermediate point between 100 and 220 yards. 
Bicycling and Walking. 
As before, the curve for men bicycling, which is drawn on twice the 
scale vertically of the running curves, is far less steep than they are. The 
conclusion from this was emphasised above. The walking curve is inter- 
esting—it is approximately straight. Physiologically speaking, there is 
not much interest in the shortest walking races, since here walking is 
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