EFFICIENCY IN GRADE WALKING. 255 



100 per cent less 9 per cent, or 91 per cent; for 55 meters, 89 per cent; 

 for 65 meters, 85 per cent; for 72 meters, 84 per cent; and for 77 meters, 

 82 per cent. The values to be deducted for the heat due to the hori- 

 zontal component, as thus computed, are given in column g. The heat 

 due to the work of ascent may then be calculated by deducting from the 

 total increment in heat over standing (column d) the heat due to the 

 horizontal component corrected for that due to the step-lift (column g) . 

 The resulting values are recorded in column h, and represent the increase 

 in heat actually ascribable to the work of ascent. Dividing these 

 values by the kilogrammeters of work of ascent (column c), we obtain 

 the increment in heat per kilogrammeter of work of ascent. This is 

 best expressed in gram-calories as recorded in column i. From these 

 latter values the efficiency of the body for the total work of ascent 

 is readily computed by using 2.34 gram-calories as the heat equivalent 

 of 1 kg. m. These percentages are given in column j, and represent 

 net efficiencies. 



From the general consideration of the efficiency of the body as com- 

 puted on the basis of grade-lift, it was found that these values repre- 

 sented an average for all of the subjects not far from 33 per cent. (See 

 table 70, p. 251.) By this new method of computation, which ascribes 

 a larger amount of work to the body, since the step-lift is superimposed 

 upon the grade-lift, we find that for this subject (E. D. B.) the per- 

 centage of efficiency is larger, in some instances actually reaching 50 to 

 60 per cent, with a maximum on November 10 of 61.6 per cent. Under 

 the separate groupings for the different speeds, the experiments have 

 been arranged in the order of increasing grade, running for the most 

 part from 5 to 40 per cent, except with the two higher-speed groups 

 when the steepest grades were but 30 and 25 per cent, respectively. 

 An inspection of the figures for these efficiencies in column j shows that, 

 in general, the percentages fall as the grade increases, i. e., within each 

 speed group there is a distinct tendency for the efficiency to be some- 

 what lower with the higher grades. 



It is more than likely that the difficulty in computing the ratio be- 

 tween the fraction of the energy expended for the grade-lift and that 

 expended for the standing and horizontal walking when an extremely 

 low grade was employed may in part account for the high values 

 here found, a point which has been touched upon in the earlier dis- 

 cussion of the grade-lift measurements. With constant grade, but 

 varying speeds, the percentage efficiency for the 10 per cent grade 

 remains practically constant throughout the entire series at 45 per 

 cent; with the 15 per cent grade they likewise are reasonably constant; 

 with a 30 per cent grade a slight decrease in the efficiency is apparent, 

 which may also be seen with the 40 per cent grade. 



The whole problem of computing the efficiency on this basis may 

 reasonably be challenged on the grounds that not only is the value of 

 the step-lift uncertain, but also we are not dealing here with "effective" 



