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SCIENCE 



[N. S. Vol. XXIX. No. 744 



ena are naturally more pronounced in those 

 persons who are physically untrained. I 

 shall not deal here in detail with the physi- 

 ology of physical training, with its result- 

 ing hypertrophy of heart and voluntary 

 muscles, and increase in strength, and in 

 quickness and accuracy of movement. But 

 I would emphasize one point, namely, that 

 a most important element in training is the 

 adaptation of the tissues to the toxic fatigue 

 substances. Without this all the other 

 benefits of trainina; would avail nothing. 

 It is well known t'nat the body can adapt 

 itself remarkably to even large quantities 

 of poisonous drugs, when those are taken 

 first in small and then in gradually in- 

 creasing doses, extending over a long 

 period. Exactly the same thing is found 

 in physical training properly conducted. 

 Moderate but increasing amounts of exer- 

 cise, producing moderate but increasing 

 amounts of fatigue substances, put the tis- 

 sues into a state of tolerance or resistance, 

 such that when the supreme effort is de- 

 manded of them, they do not succumb. 

 He who wins is he who can best resist the 

 poisons of fatigue. 



What now is the teaching of physiology 

 regarding physical exercises and physical 

 contests ? 



In the first place, physiology teaches that 

 the hiiman body is capable of responding 

 to enormous demands for physical effort. 

 One's latent power in all of the three varie- 

 ties of physical exercise— of strength, of 

 speed and of endurance— is never realized 

 except in emergencies, and then it often 

 proves remarkable. 



Secondly, physiology teaches the great 

 value of proper training in increasing one 's 

 latent power. Yet training can easily de- 

 feat its object. As Darling rightly says: 



The physiological effects of training, on the 

 heart and kidneys in particular [and we might 

 add, on the nervous system], may approach un- 

 pleasantly near to pathological conditions. 



The physiological basis of overtraining 

 is not altogether clear, but the fact of over- 

 training is undeniable. 



Thirdly, physiology teaches that the fa- 

 tigue of one tissue from over-use means the 

 fatigue of all tissues. Extreme activity of 

 the muscular system involves not only les- 

 sened muscular, but also lessened mental 

 activity. 



Fourthly, physiology bids us to beware 

 of physical excess. According to Tissie 

 there are three degrees of fatigue — slight 

 fatigue or lassitude, which gives tone to the 

 body; fatigue which irritates, excites and 

 enervates ; and fatigue which weakens ; and 

 he adds that the two latter degrees of fa- 

 tigue should be absolutely avoided. With 

 this view I can in general agree, and yet I 

 would not here be an extremist. If I read 

 aright the teachings of physiology, they are 

 that physical exercise, carried to the point 

 at which it produces extreme fatigue, and 

 persisted in, can not fail to be harmful. 

 The human body is, indeed, wonderfully 

 resistant and capable of apparently com- 

 plete recovery after a considerable degree 

 of abuse. But it is not to be denied that 

 extreme physical exertion is a debauch and, 

 like any other debauch, leaves the indi- 

 vidual mentally, morally and physically 

 depleted. It is also not to be denied that 

 the chances of continued well-being are 

 enhanced if the debauch is never indulged 

 in. No sharp line can be drawn between 

 what is normal and what is pathological in 

 fatigue. What is normal for one person 

 may be pathological for another. Training 

 should extend the boundaries of the normal. 

 But it is safest to avoid those physical exer- 

 cises that force the organism to the border 

 line beyond which the abnormal lies. The 

 one may pull his all in the tug of war or 

 wield his oar in the four-mile race, or run 

 his twenty-five Marathon miles. But it is 

 the physically exceptional man who can do 

 these things, and the physically average 



