U7G113NE OF THE MUSCLES. 89 



like a pendulum once its foot is raised from the ground. 



IAs short pendulums swing faster than long ones the natu- 

 ral step of short-legged people is quicker than that of 

 long-legged. 



Running differs from walking in several respects. 

 There is a moment when both feet are off the ground ; 

 the toes alone come in contact with it at each step ; and 

 the knee joint is not straight at the end of the step. In 

 running, when the rear foot is to leave the ground the 

 knee is suddenly straightened, and the ankle-joint extend- 

 ed so as to push the toes forcibly on the support and pow- 

 erfully impel the whole body forwards and upwards. The 

 knee is then considerably flexed and the foot raised some 

 way from the ground, and this occurs before the toes of the 

 front foot reach the support. The raised leg in each step is 

 forcibly drawn forward by its muscles and not allowed to 

 swing passively as in quiet walking. This increases the 

 rate at which the steps follow one another, and the stride 

 is increased by the sort of one-legged jump that occurs 

 through the jerk given by the straightening knee of the 

 rear leg, just before it leaves the ground. 



Hygiene of the Muscles. The healthy working of the 

 muscles is dependent on a healthy state of the body in 

 general ; this is indispensable that they may be sufficiently 

 supplied with proper nourishment, and have their wastes 

 promptly carried away. Hence good food and pure air are 

 necessary for a vigorous muscular system. Muscles also 



"Why do short legged persons tend to take a quicker step than 

 others? 



How does running differ from walking? Describe the act of run- 

 ning. How is the number of steps taken in a given time increased in 

 running? How is the stride increased? 



How does the state of general health influence the muscular sys- 

 tem? Why does an athlete need good food and air? 



