128 THE HUMAN BODY 



the natural step of short-legged people is quicker than that of 

 long-legged ones. 



In fast walking the advanced or supporting leg also aids in 

 propulsion; the muscles passing in front of the ankle-joint con- 

 tracting so as to pull the Body forwards over that foot and aid 

 the push from the rear foot. Hence the fatigue and pain in front 

 of the shin which is felt in prolonged, very fast walking. From the 

 fact that each foot reaches the ground heel first, but leaves it toe 

 last, the length of each stride is increased by the length of the foot. 



Running. In this mode of progression there is a moment in 

 each step when both feet are off the ground, the Body being un- 

 supported in the air. The toes alone come in contact with the 

 ground at each step, and the knee-joint is not straight when the 

 foot reaches the ground. When the rear foot is to leave the sup- 

 port, the knee is suddenly straightened, and at the same time the 

 ankle-joint is extended so as to push the toes forcibly on the 

 ground and give the whole Body a powerful push forwards and 

 upwards. Immediately after this the knee is greatly flexed and 

 the foot raised from the ground, and this occurs before the toes of 

 the forward foot reach the latter. The swinging leg in each step 

 is violently pulled forwards and not suffered to swing naturally, 

 as in walking. By this the rapidity of the succession of steps is 

 increased, and at the same time the stride is made greater by 

 the sort of one-legged leap that occurs through the jerk given by 

 the straightening of the knee of the rear leg just before it leaves 

 the ground. 



Leaping. In this mode of progression the Body is raised com- 

 pletely from the ground for a considerable period. In a powerful 

 leap the ankles, knees, and hip-joints are all flexed as a pre- 

 paratory measure, so that the Body assumes a crouching atti- 

 tude. The heels, next, are raised from the ground and the Body 

 balanced on the toes. The center of gravity of the Body is then 

 thrown forwards, and simultaneously the flexed joints are straight- 

 ened, and by the resistance of the ground, the Body receives a 

 propulsion forwards; much in the same way as a ball rebounds 

 from a wall. The arms are at the same time thrown forwards. 

 In leaping backwards, the Body and arms are inclined in that 

 direction; and in jumping vertically there is no leaning either way 

 and the arms are kept by the sides. 



