CERTAIN MOVEMENTS IN MAN 167 



indicate, according to the object in view, the best 

 way of utilizing muscular force in walking or running : 

 whether it be to traverse the greatest distance with 

 the least expenditure of energy, or whether it be to 

 cover a certain distance in the least possible time. 

 Attention should not only be directed to the kind of 

 pace, running or walking, for instance, but also to the 

 number of steps to be taken in the minute. 



It has already been pointed out (Fig. 109) that, in 

 walking rapidly, from 70 steps per minute onwards, the 

 expenditure of energy rapidly increases, and that in 

 running the total energy is considerably greater when 

 the number of steps per minute are few, but commences 

 to diminish when the frequency of step increases, and 

 finally again increases. There is, then, for each pace 

 an optimum rate of steps per minute, which corresponds 

 to the point at which the velocity increases propor- 

 tionately faster than energy is expended. 



There are other points to be considered in choosing 

 a pace. Energy must not be exhausted so quickly 

 that the muscles have not time to recover from the 

 effects of fatigue. A lon^ walk, in which a £i*eat deal 

 of energy has been expended, may be borne with im- 

 punity, while rapid running would soon exhaust the 

 muscular strength, although the total expenditure of 

 energy may be much less. 



As the studies just described have only been made in 



If the rate of step is rapid, a slight extension is afforded to the oscilla- 

 tions by the short duration assigned to it. Thus, in walking, ilie 

 amplitude of the vertical oscillations of the body is related to the 

 length of step ; it is independent of the length in running ; in fact, an 

 invrrse relationship can almost be detected. 



C. Variation* in the Amount of Worl; don*, in the Arcel V ration and 

 Slowing of the Horizontal Translation 'of th^ Boil;/. — 1 his factor in the 

 work increases fairly regularly with the rate and length of the step. 

 In running, it assumes considerable proportions, although the absolute 

 variations in speed are slight. This is because the gain or loss of vital 

 energy is in proportion to the difference of the squares of the maximum 

 and minimum velocities of translation. 



