WALKING, RUNNING, AND SPRINGING. 



507 





thick lines) ; the centre of gravity is now transferred to this active leg, which, at the same time, 

 is slightly flexed at the knee, and placed vertically. The first act is then repeated. 



Simultaneous Movements of the Trunk. During walking, the trunk performs certain 

 characteristic movements. (1) It leans every time towards the active leg, owing to the traction 

 of the glutei and the tensor fasciae lata?, so that the centre of gravity is moved, which in short 

 heavy persons with a broad pelvis leads to their "waddling" gait. (2) The trunk, especially 

 during rapid walking, is inclined slightly forward to overcome the resistance of the air. (3) 

 During the "pendulum-like action," the trunk rotates slightly on the head of the active femur. 

 This rotation is compensated, especially in rapid walking, by the arm of the same side as the 

 oscillating leg swinging in the opposite direction, while that on the other side at the same time 

 swings in the same direction as the oscillating limb. 



Modifying Conditions : 1. The Duration of the Step. As the rapidity of the vibration of a 

 pendulum (leg) depends upon its length, it is evident that each individual, according to the 

 length of his legs, must have a certain natural rate of walking. The "duration of a step" 

 depends also upon the time during which both feet touch the ground simultaneously, which, of 

 course, can be altered voluntarily. When "walking rapidly" the time = 0, i.e., at the same 

 moment in which the active leg reaches the ground, the passive leg is raised. 2. The length 

 of the step is usually about 6 to 7 decimetres [23 to 27 inches], and it must be greater, the 

 more the length of the hypothenuse of the passive leg exceeds the cathetus of the active one. 

 Hence, during a long step, the active leg is greatly shortened (by flexion of the knee), so that 

 the trunk is pulled downwards. Similarly, long legs can make longer steps. 



According to Marey and others, the pendulum movement of the passive leg is not a true 

 pendulum movement, because its movement, owing to muscular action, is of more uniform 

 rapidity. During the pendulum movement of the whole limb, the leg vibrates by itself at the 

 knee-joint (Lucas, H. Vierordt). 



Fixation of the Femur. According to Ed. and W. Weber, the head of the femur of the 

 passive leg is fixed in its socket chiefly by the atmospheric pressure, so that no muscular action 

 is necessary for carrying the whole limb. If all the muscles and the capsule be divided, the 

 head of the femur still remains in the cotyloid cavity. Rose refers this condition not to the 

 action of the atmospheric pressure, but to two adhesion surfaces united by means of synovia. 



Fig. 350. 



Instantaneous photograph of a runner {Marey). Ten pictures per second. The abscissa 



indicates the length of the step in metres. 



The experiments of Aeby show that not only the weight of the limb is supported by the 

 atmospheric pressure, but that the latter can support several times this weight. When traction 

 is exerted on the limb, the margins of the cotyloid ligament of the cotyloid cavity are applied 

 like a valve tightly to the margin of the cartilage of the head of the femur. According to the 

 Brothers Weber, the leg falls from its socket as soon as air is admitted by making a perforation 

 into the articular cavity. 



Work done during Walking. Marey and Demery estimate the amount done by a man 

 weighing 64 kilos. [10 stones], when walking slowly, as = 6 kilogrammetres per second; rapid 

 running = 56 kilogrammetres. The work done is due to the raising of the entire body and 

 extremities, to the velocity communicated to the body, as well as to the maintenance of the 

 centre of gravity. 



In springing or leaping, the body is rapidly projected upwards by the greatest possible and 

 most rapid contraction of the muscles, while at the same time the centre of gravity is maintained 

 by other muscular acts (fig. 351). 



The pressure upon the sole of the foot in walking is distributed in the following manner : 

 The supporting leg always presses more strongly on the ground than the other ; the longer the 

 step the greater the pressure. The heel receives the maximum amount of pressure sooner than 

 the point of the foot (Carlet). 



