Man's Mechanical Efficiency in Work Performance. 403"» 



The Cost of Movement. 

 Formulation of the Cost. 

 It is a matter of common knowledge that the " cost of movement " increases 

 with increasing body weight. It is therefore different from the cost of 

 work performance, for which heavier individuals are chosen for the continued 

 performance of heavy work. That the fact is a very definite one may be- 

 seen at once from the residues of my four cycling subjects on p. 401. For 

 brevity those residues (Group B) are at once expressed in terms of the 

 individual " stripped weights " of the four subjects subsequent to conversion 

 from kalories per hour into small calories per second (division by 3"6). 



(1) Kemp Q = 0-1114 W 1-438 , 



(2) Eae Q = 04096 W 1 " 438 , 



(3) Bennett Q = 0-1053 W 1 " 438 , 



(4) Armstrong Q = 0-1114 W 1 " 438 , 



and at the same rate of movement (see Table I, 2 strides per second), 



(5) Briscoe Q = 0-0991 W 1 " 438 . 



Taking the average of the first four, obtained under the same experimental' 

 conditions, it may be said that at this rate of movement (one cycle revolu- 

 tion, or two strides per second), 



Q = 0-1094 W 1 ' 438 . («> 



And now turning to the influence of the rate of movement on this cost, 

 it is also certainly very definite, even if complex. Thus the whole of the 

 Douglas data (Table II) may reasonably be considered as expressible in 

 the following formula : — 



H = 52-37 (1-475 V)°' 380V , (6), 

 as is shown by a comparison of the data, 



(1) 210, 164, 131, 88-5, 63, 

 with the values deduced from the formula, 



(2) 210, 166, 133, 88, 63. 



As a matter of fact, it is possible to make a choice between this formula 

 and others of a somewhat similar type, equally, if not more, satisfactory for 

 this purpose, but this formula has been deliberately chosen as of a certain 

 greater rigidity of type which is of value when comparisions are made with 

 attempts to formulate the cost of other movements. Thus, for example, the 

 whole of the Briscoe data can be reasonably held to be expressible in an 

 exactly similar, and similarly rigid, formula as follows : — 



Q = 16-45 (1-783 V) ' 2,i0V , (c) 



