390 THE HUMAN MOTOR 



the sum of the energy expended in the equivalent horizontal 

 distance and vertical ascent (vide para. 278). 



The descent of an inclined plane is a somewhat complex pheno- 

 menon. The expenditure of energy increases slightly with the 

 declivity. With an inclination of 8 cm. the energy increases with 

 the load, while, with an inclination of 13 cm. it decreases ! If we 

 compute the expenditure of energy in the vertical descent we 

 have : in the first case 



85 -41 



= 5-5 small calories per kilogrammetre. 



08 

 In the other case, 



_= 4-53 small calories per kilogrammetre. 



This reduction is more noticeable if the subject is loaded. 

 Detailed investigation is needed to arrive at the most economical 

 conditions for so complex a form of locomotion. All that we can 

 now say is that if the labourers have to carry loads down a plane 

 and return unloaded up the plane, it is best that the inclination 

 should be fairly steep, about 13 cm. rise per metre. 



299. The Descending Walk. It will be remembered that 

 Chauveau, by a series of very consistent experiments, proved 

 that the expenditure of energy is less in the (resistant) work of 

 descent than in the (motor) work of ascent. The ratio is 52 : 

 100 at ordinary speeds (vide 140). We have just seen that this 

 ratio is 85 : 100 in the case of unloaded descent down a slope of 

 8 cm. per metre. With load, on the same slope, the ratio is 75 : 

 100. If the slope is 13 cm. per metre the ratio is almost the same 

 as that obtained by Chauveau (for no load) . With load the ratio 

 is reduced to 38 : 100. 



300. Comparison between Horizontal and Vertical Walking. 



It has been shown that the expenditure per kilogramme per metre 

 traversed horizontally is -51 c., and that in ascending a stairway 

 is 8 c. approximately. Hence the ratio between the kilogram- 



o 



metre and the metre-kilogramme is - ='16 approximately. 



*ol 



However, it was found that one of the subjects of the experi- 

 ments could, for the same total expenditure of energy per diem, 

 achieve no less than 2,220,738 metre kilogrammes in hori- 

 zontal walking or 69,027 kilogrammetresin ascending and descend- 

 ing a stair, f 1 ) The ratio in this case was 20. The load carried was 

 45 kg. and the speed and periods of work and repose were irregular. 



(*) Jules Amar, Le Rendement, p. 74. 



() Haughton (S.). Principles of Animal Mechanics, 1873. 



