LOCOMOTION 353 



was 0'75 m. The average time of a single pace was therefore 

 495 seconds and the rate of walking 5*445 km. per hour. 



Commence at the moment when the right foot leaves the 

 ground and is in the air, the left leg is in front and a pace has been 

 made, the trunk is poised over that leg, and the period of 

 " support " and " propulsion " begins. The right leg, which is 

 lifted, is shortened by flexion of the knee (the angle is 150), so 

 that it can oscillate. The knee then stiffens, the thigh moves 

 forward to an angle of 25 with the vertical, and the heel of the 

 right foot makes contact with the ground. It should be remem- 

 bered that this return to the ground is made slowly, without 

 acceleration, the muscles having moderated the pendulum effect 

 that Weber believed to govern the oscillations of the legs. 

 Theoretically, it would be a pendulum of a period : 



I being the moment of inertia ( 26) ; this would lead to : 



' = * V il^Ws = ' 56s - 



too high a value. There is therefore muscular action which 

 Fischer found to be greater than 

 that of gravity. It is due first of 

 all to the flexors of the lower 

 leg, then to those of the thigh 

 on* the pelvis, and finally to 

 the quadriceps which contract 

 sharply and throw the leg for- FJG 



ward, the sole of the foot bend- 

 ing to soften the shock of contact with the ground. Again, in 

 the period of oscillation, the point of support of the limb, at the 

 hip, is not fixed, but advances by a step which could be repre- 

 sented by the diagram (fig. 251). The hip has moved from 

 O to O', and the leg OA to O'A'. The duration of the oscillation 

 corresponds to the distance BA' and the angle of the oscillation 

 is only equal to a, not to 2a. In the example taken by Braune 



and Fischer t = ,-^r of a second, AB = 0-778 m., and OA = 



0-870 m. If the triangle AOB is equilateral a would equal 60, 

 in this case 



fin 

 a = - ; A = 53-60 approximately, 



o7U " 



which leads to an average angular speed of : 



53-60 X 1,000 10QO 



- TTK ~~ == A ^ y ' 

 415 



