418 



THE HUMAN MOTOR 







F 1G . 287. - 



Best position for working at the vice. 



The feet were placed in the positions shown, and the distance 

 was measured from the umbilicus (G) to the vice. The workman 

 was at rest, but he held the file on the work in the same position 

 as if he was about to commence a stroke. The oxygen consump- 

 tion for various distances was : 



Distance in centimetres 15 20 25 30 



Oxygen consumption in litres 1-045 1-03 1-036 1-07 



The best distance, from this point of view, was, therefore, 20 cm. 

 (vide fig. 287). 



The relative positions of the feet shown in the above fig., 

 namely, a distance of 25 cm. between the heels and an angle of 

 68 between the centre lines of the two feet was found to be the 

 best for the subject " A.C." It must, however, be admitted that 

 most workmen do not adopt such a position. They bring the 

 left foot further forward and place the feet nearer together. 

 They also lean slightly on the vice. It is clear that 

 such an attitude calls for certain static efforts, the cumulative 

 effect of which may be quite appreciable. Thus our experimental 

 observations may be the means of improving the usual methods 

 of working. 



315. The Economical Use of the File. After some little prac- 

 tice the journeyman fitter, A.C., became quite accustomed to this 

 attitude, which the writer considered to be the most favourable. 



In this attitude, as previously described, the workman held 

 himself quite upright and placed his feet in the relative positions 

 shown in fig. 287, the weight of the body resting chiefly on the 

 left leg. The hands were applied to the file in the usual way, 

 while care was taken that no pressure wa's applied during the 

 return strokes. Under these conditions a speed of 70 strokes 

 per minute gives the best economy. At this speed the output 

 of work is steady, the fatigue relatively small, the respirations 



