CERTAIN MOVEMENTS IS MAX 161 



kilogrammetrcs. 



Translation of the lower limb Hi 



Vertical oscillations of the body 2 3 



Acceleration nn<l remissions in velocily in the 



horizontal direction IS 4 



Total ... 241 



Thus the expenditure of energy in taking half a 

 step on level ground varies according to the gait from 

 9 to 24 kilogrammetres. If account is kept of the 

 number of steps taken in a minute in these two 

 extreme cases, the expenditure of energy will be found 

 to be, in slow walking 720 kilogrammetres, and in 

 rapid running 6748 kilogrammetres, which represents 

 about 12 kil >grammetres per second in the first case, 

 and 112 kilogrammetres in the second.* 



* We knew perfectly well that walking on level ground represented 

 the expenditure of a certain amount of energy, and tried to estimate 

 the exact amount, but that did nut necessarily imply any difference 

 of opinion between physicists and physiologists. If physicists only 

 took account of the energy expended in walking when the road was 

 inclined, it was because only in this case could tiny ascertain the 

 exact amount of work done, namely, that required for lifting the 

 body weight through a certain number of metres, or lowering it as 

 the case might be. 



But Coulomb knew full well that both in walking and in carrying 

 burdens the muscles developed energy and did work, but not being 

 able to reduce this expenditure of energy to the usual formula PH, 

 he gave it the name of '* Useful effect," (PE), that is to say, the wt ight 

 multiplied by the distance traversed. In short, the measurement of 

 energy in walking and running on level ground demands a complete 

 knowledge of the movements transmitted to the body and limbs as 

 the foot is lifted from the ground. 



It was for physiologists to determine these movements, ami as 

 we have seen, chronophotography afforded them an excellent means 

 of so doing. 



In giving the above measurements of the work performed in walking, 

 we said that they probably represented the maximum, and that their 

 real value was perhaps something less. This is because in alternate 

 movements in contrary directions there may be a certain storage of 

 energy in the organs which execute the movements, and consequently 

 there may be a certain suppression of energy which would other- 

 wise be expended, and consequently in the succeeding action there 

 may be a certain amount of restitution. To make our point clear, 

 let us take the case of an elastic ball falling on a hard surface 

 from a certain height. Let us suppose the ball weighs 100 grams, 

 and that it falls through a distance of one metre. As the ball readies 

 the ground, the action of gravity will have produced work to the 



