PEND UL UM MO VEMENTS OF THE LIMB. 2 6 9 



duration of a stride * and its length, the longer strides being taken in the 

 shorter periods of time. 



The Webers also investigated this relationship in the case of a 

 running man, and found that the duration of the stride suffered but 

 slight variations, and that in consequence differences of velocity are due 

 chiefly to differences in the length of stride. 



Marey investigated this matter by somewhat improved methods, and 

 found that, as the number of steps was increased in walking from 40 to 

 75, the length of the stride was increased, too, but that in still quicker 

 walking the length diminished very considerably. 



In the face of this conflicting evidence, it is difficult to believe in any 

 necessary relationship between the length of a stride and its duration. Indeed, 

 without any scientific appliances at all, we can convince ourselves that the step 

 can voluntarily be lengthened and shortened at will within very wide limits, 

 without changing the duration of the pace. It is very questionable whether 

 we can accept either the Webers' or Marey's results as true, except for the 

 particular experiments which they carried out. For instance, in Marey's 

 experiments, the subjects of experiment were required to walk in time with the 

 sound of a bell struck at regular intervals. Knowing the distance traversed, 

 and the time which this took, the mean length of the stride could be 

 calculated. The men — they were soldiers — when they had to walk to a 

 quicker time would instinctively lengthen the pace, the object of quick time 

 being to get over ground, and this they were able to do up to a certain limit. 

 We may indeed walk or run in many fashions, and even the Webers 

 recognised that the time relationship between length and duration of pace was 

 not the same in " Sprunglauf" as in " Eillauf." Nevertheless, there is probably 

 for each individual a walking and running pace of certain duration involving 

 the least expenditure of energy. The step is quicker in short than in tall per- 

 sons, and the reason for this will be apparent on perusal of the next section. 



Pendulum movements of the limb. — The Webers 2 taught that, in 

 walking or running, the forward movement of a limb, from the moment 

 at which it is lifted from the ground to the moment it readies it again, 

 is a pendulum-swing, due not to the action of muscles but of gravity 

 itself. This view is generally held to be true, and some writers such as 

 A. Fick 3 consider that the swings of a hanging thigh are merely damped 

 by the surrounding muscles, which alter the amplitude but not the 

 period of the swing : they would deny the aid of muscles altogether. 



The evidence in favour of this theory is as follows : — The lower limb 

 hanging lax and allowed to swing has a period of - 692 seconds. In walk- 

 ing or running, half a swing is executed by each limb during the period 

 of a single pace, and a whole swing during the period of two paces. 

 This is true especially in the case of rapid running, when the feet touch 

 the ground and remain at rest for a very short period of time. Now 

 two such paces are accomplished in - 664 seconds, rather less, in fact, 

 than the time taken by the swing of a lax leg. This somewhat shorter 

 duration is accounted for, by those who advocate the pendulum theory, 

 by the fact that in running the leg is flexed, and that on this account 

 the period of its swing would be diminished. Again, it is maintained by 

 the followers of the Webers that by the pendulum theory alone can 

 the fact be explained that the longer the stride the shorter is the period 



1 The length of a stride is the distance, say, between the point of the toe of one foot as it 

 leaves the ground, and the point of the other foot when it, in its turn, leaves the ground. 



2 "Meclianik der Gehwerkzeuge." 



3 Hermann's "Handbuch," Bd. ii. Th. 1, S. 330, 331. 



