EFFICIENCY IN GRADE WALKING. 253 



EFFICIENCY IN WORK OF ASCENT. 



The total heat-output during grade walking is made up of a number 

 of factors: first, the basal requirement for standing; second, the super- 

 imposed work of forward progression, including the step-lift; and third, 

 the actual elevation of the body as a result of the grade. A computa- 

 tion of the proportion of energy ascribable to the actual lifting of the 

 body, such as is done not only in the grade-lift but in the superimposed 

 step-lift, necessitates the deduction of certain basal values. Of these, 

 obviously that for the standing metabolism would be one, but the 

 deduction of the standing metabolism only does not allow for the 

 energy of forward progression. Ordinarily, the entire energy due 

 to horizontal walking is deducted before the efficiency for grade walk- 

 ing is computed, but this is illogical, since the energy required for 

 forward progression includes a not inconsiderable proportion rightly 

 attributable to the elevation of the body in the step-lift, which is an 

 integral factor in grade walking. When the increments in the total 

 heat of horizontal walking over the requirement for the standing 

 position are compared with the computed heat ascribable to the work 

 done by the body in the step-lift, it is seen that the heat-output due to 

 this secondary elevation of the body was an appreciable percentage of 

 the total increase in energy and varied with the speed at which the 

 man walked. (See table 43, p. 159.) Consequently, in computing 

 the efficiency for the work of ascent, a deduction should be made from 

 the total heat-production of a certain proportion of the energy required 

 for horizontal walking at a similar rate, this deduction depending upon 

 the speed of walking. 



It has seemed unwise to use all of our data in computing the effi- 

 ciency for the work of ascent, inasmuch as the method of computation 

 is at best based upon problematical assumptions. We have, however, 

 computed the efficiency for a number of typical days with E. D. B. at 

 varying grades and speeds. These results are recorded in table 72. 

 This table is best considered in relation to table 55 (p. 209), the data in 

 columns a to e being drawn from that table. The work of the total 

 lift of the body, that is, the work of ascent, which includes both the 

 grade-lift and the step-lift in grade walking, is recorded in column c. 

 The total increment in the heat over standing in column d represents 

 the total heat measured during the grade walking, less the standing 

 requirement. The total heat due to the horizontal component is 

 recorded in column e and, as originally recorded in table 55, was 

 obtained by first multiplying the weight of the body by the horizontal 

 component of the distance walked and then multiplying the result by 

 the factor for the energy required for each horizontal kilogrammeter 

 (column n of table 55). 



The first important new step is the computation of the heat due to the 

 horizontal component, less that fraction due to the step-lift in walking 



