FACTORS INFLUENCING EFFICIENCY 



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muscular motions incidental to riding with weight are common 

 to both determinations. Such a comparison is that obtained 

 when there is a change from a moderate to a heavy load. As 

 will be noted from the above summary of efficiencies the average 

 efficiency under these conditions is about 30 per cent. 



There is a certain amount of evidence available which would 

 suggest that the degree of efficiency obtained varies with the 

 groups of muscles used in performing the work. The efficiency 

 of muscles less commonly in use than the leg muscles is some- 

 what lower, flexor groups may differ from extensor groups, etc. 

 The state of training, too, probably influences, although apparently 

 not very markedly, the degree of efficiency. And finally, some 

 workers maintain that the efficiency may 

 also be, to some extent, dependent on the 

 nature of the diet. Macdonald maintains 

 that the efficiency of muscular work is a 

 function of body mass. 



Greenwood, who has carefully analysed 

 the data obtained by many of the workers, 

 has come to the conclusion that although 

 as yet no law can be formulated connecting 

 heat production and work performance, 

 within fairly wide ranges, simple formulae 

 of linear regression do describe the relations 

 subsisting between heat production, body 

 mass and work performance, with an 

 accuracy sufficient for such purposes as 

 roughly computing the energetic needs of 

 workers doing the kind of work studied. 



In addition to the above-mentioned factors which influence 

 efficiency there are certain others connected with the performance 

 of the work itself which apparently play a determining part. 

 These are load and speed. 



Although it might be presumed that load would exercise a 

 marked influence, such experimental work as exists tends to show 

 that increase of load zvithin limits does not materially influence 

 the efficiency of the body. There is, however, a slight tendency 

 for the work to be done more efficiently when the load is changed 

 from a moderately heavy to a heavier one than when the change 

 is from a light to a heavy load. 



The influence^ of speed, that is, the rate at which the work is 

 done in unit time, is of much greater moment. Experimentally 

 it has been found that the total energy expenditiu-c per revolution 

 of the pedals is constant for all speeds, but that although there is 



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