Our Bodies 333 



accomplishing much labor. Violent exercise should be avoided since 

 it may injure the organs of the body. Exercise should be taken at 

 regular hours daily if the best results are to be had. Spasmodic 

 efforts to increase muscular power usually fail of their purpose. 

 It should be borne in mind that strength is of gradual growth 

 which can be gained only by systematic, well-regulated exercise. 



Kinds of Exercise. Among the most common kinds of exer- 

 cise are walking, running, jumping, swimming, rowing, riding, and 

 games. The kind of exercise to be chosen depends, of course, on 

 the strength and taste of the individual and the time he can give 

 to it. 



Walking is a form of exercise always available for people in 

 health, and love for it should be cultivated by the middle-aged and 

 the old as well as by the young. In England, walking is much 

 more popular than in this country. In order to produce any 

 hygienic result, however, walking must be brisk, and must be con- 

 tinued long enough to produce the physical and chemical changes 

 in the tissues that come with vigorous muscular exercise. Mere 

 strolls are not sufficient. Tramping and mountain climbing are 

 effective. 



Running requires more violent effort than walking and should 



not be indulged in to the point ^____ i 



of exhaustion. This kind of 



exercise is especially fitting for 



young people, provided it is 



not carried on for so long a 



time as to overwork the heart. 



Many athletic games and 



sports involve more or less 



running and they are usually 



entered into with great enthu- 



siasm and with favorable re- A CLOSE HALF ' MILE! 



suits to health, except in cases where the spirit of rivalry leads to 



extreme tests of endurance. 



Running demands the expenditure of a large amount of vital 

 force. Physically it is a very expensive means of movement. 

 Speed cannot be acquired without the contraction of the muscles 



