From the New York Times, February 24, 1909:

Marathon Racing Dangerous

There is reason for viewing with considerable apprehension the sudden popularity of the so-called Marathon race—a race, that is, in which the competitors are men or boys and the distance is something over twenty-six miles.

In this vicinity, where athletic sports are for the most part conducted under the more or less intelligent regulations of organized clubs, participation in these contests is usually freed form some of its dangers by barring from them would-be entrants who do not meet certain fixed rules as to age and health. Even here, however, the fact that the restrictions are not sufficiently stringent is made obvious by the number of racers who fall out before the distance is covered or who reach the goal in a state of complete physical exhaustion.

It is only exceptional men who can safely undertake the running of twenty-six miles, and even for them the safety is comparative rather than absolute. The chances are that each one of them weakens his heart and shortens his life, not only by the terrible strain of the race itself, but by the preliminary training which produces muscular and vascular development that become perilous instead of advantageous the moment a return to ordinary pursuits and habits puts an end to the need for them. For the great majority of adults, particularly in an urban population, to take part in a Marathon race is to risk serious and permanent injury to health, with immediate death a danger not very remote, and it is little better than criminal to let growing boys make any such demand upon their powers of endurance. For boys, indeed, even the shorter races are of very questionable desirability, since at any distance the expenditure of energy under the stimulus of competition is excessive.

Exercise in the open air is an admirable thing, no doubt, but the common notions as to its object and result are pretty nearly all wrong. The truth is that exercise should always be purely subordinate to the business and pleasure of life. To make it or the bodily changes it produces ends instead of incidents is a dangerous as well as an absurd mistake.