248 METABOLISM DURING WALKING. 



in a direction perpendicular to the inclined plane of the belt as it does 

 when the fork is parallel to the belt. It is assumed, therefore, in sub- 

 sequent discussion, that the step-lift as actually measured and re- 

 corded in this publication is not far from correct, though probably 

 somewhat below rather than above the true value. 



WORK OF ASCENT. 



In addition to the work which the subject performed of lifting the 

 body-weight to the elevation produced by the grade of the treadmill, 

 ordinarily considered as the only positive work done in grade walking, 

 we must also take into account the work which was done (theoretically, 

 at least) in lifting the body a few centimeters at each step in the rise 

 and fall of the body due to the step-lift. That the work of grade-lift 

 is positive and, in the transportation of a superimposed load up a road, 

 may be of economic significance, must not obliterate the fact that 

 physiologically, if the body, or indeed a superimposed load, is lifted a 

 few centimeters during each step, positive work is being accomplished, 

 uneconomical though it may be. The sum of the work due to the step- 

 lift and that due to the grade-lift represents what may therefore be 

 designated as the "work of ascent." From the step-lift as actually 

 measured and the weight of the body, the work performed as a result 

 of the step-lift has been computed and is recorded in column h of tables 

 52 to 55. The "work of ascent" is given in column i ol the same tables. 



In considering the work done during grade walking, we may see from 

 previous discussion that, owing to the uncertainty as to the actual 

 amount of work due to the scep-lift, the exact apportionment of the 

 total work between that due to the elevation of the body in the grade- 

 lift and that due to the step-lift is difficult. Doubtless a more subtle 

 analysis of the mechanics of locomotion in the line of the particularly 

 ingenious method of Braune and Fischer, 1 possibly, by means of 

 specially illuminated and figured backgrounds, and the ultra-rapid 

 motion-picture camera, may clarify the situation. Since this may 

 not be made at the present time, and it is desirable to present a hitherto 

 neglected factor in the computation of the efficiency of the body in 

 grade walking, we have assumed that, as a result of the experiments 

 carried out as this report was being written and the considerations 

 set forth on pages 243 to 244, the measurements of the step-lift obtained 

 in this research during grade walking included none of the elevation 

 due to the grade-lift component, and they thus represent the true 

 step-lift. The computations of the work due to this factor which 

 have been made from them may thus be considered as giving the true 

 results. 



1 Braune and Fischer, Abhandl. d. math.-phys. Klasse d. Konigl. Sachsischen Gesellsch. d. 

 Wissensch., Leipsic, 1895, 21, p. 153. 



