EXERCISE. 55 



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and the lungs have to get rid of the extra waste matters 

 (Chap. XV.). You know that after running fifty yards 

 at full speed, you find yourself breathing faster and your 

 heart beating quicker. If you are used to such racing, 

 you soon get your breath again, and your heart quiets 

 down; for those organs, having been gradually trained to 

 work just as your muscles need their help, do it easily and 

 comfortably. But if a boy who is not used to running 

 starts off on a fast race, he soon has to stop, panting for 

 breath, feeling his overstrained heart thumping in his 

 chest, and probably with "a stitch in his side." Exercise 

 leading to such results does harm. A healthy boy usually 

 gets all right again in half an hour or so; but quite often 

 fatal disease of the heart has been caused, even in strong 

 young persons, by prolonged violent exercise to which 

 they were not accustomed. Girls have in several cases 

 died in consequence of excessive exercise with the skip- 

 ping-rope. Running to catch a train has often produced 

 serious and lasting heart-disease in those who were weak 

 or no longer young, and who were unused to such mus- 

 cular exertion. 



An occasional long walk at a moderate rate, or leisurely 

 rowing a boat for an hour or two, if followed by a good 

 rest, will not injure any one in ordinary fair health: those 

 whose pursuits confine them to a desk most days are 

 usually benefited by such exercise once a week. But 

 fast running, or foot-ball playing, or rowing a race, should 

 never be undertaken by those who have not gradually 

 educated their bodies to bear violent exercise. 



may you notice after running? What happens if a boy undertakes 

 violent exercise without training? What organ is apt to be especially 

 injured by unusual muscular exertion ? Why is it better to miss a train 

 than race to catch it if you are not used to running ? 



