EXPERIMENTS WITH HORIZONTAL WALKING. 157 



cm. per meter; at 55 meters, 2.31 cm. ; at 65 meters, 3.06 cm. ; at 72 me- 

 ters, 3.29 cm.; and at 77 meters, 3.61 cm. These values show, there- 

 fore, that the step-lift per meter of distance traveled was somewhat less 

 at the lower speeds. This fact is contrary to the evidence in several 

 of our experiments, from which it appeared that the energy expendi- 

 ture per horizontal kilogrammeter tended to be somewhat greater at 

 the extremely slow speeds. This again emphasizes the importance of 

 studying more in detail the physiology of walking at slow or "saunter- 

 ing" speeds. 



STEP-LIFT PER STEP. 



It is possible that the change in number and length of steps to obtain 

 a desired speed might not affect the lift per step and that it would re- 

 main relatively uniform. An inspection of the figures for the lift per 

 step in table 41 shows that the same variations are present here that 

 were found in the number of steps and in the total step-lift per minute. 

 Not only are there variations between individuals for the same speed, 

 but for the same individual at the same speeds on different days varia- 

 tions appear which, though not large in themselves, amount to as much 

 as 20 per cent of the total step-lift per minute. Thus W. K, walking 

 at a speed of 62.3 meters per minute, had a step-lift per step on March 9 

 of 0.88 cm. and on March 29 of 1.07 cm., with a difference of 0.19 cm., 

 or 21 per cent. With the faster speeds, the step-lift is greater when the 

 extreme speeds are compared, but with the slower speeds there are 

 numerous instances when there was a greater step-lift per step than 

 with speeds a few meters faster. In the long series with E. D. B. it 

 appears that all speeds over 70 meters per minute were accompanied by 

 a step-lift per step of 2 cm. or more, and with two exceptions, speeds 

 under 50 meters per minute had a step-lift per step of less than 1 cm. 

 The high values for January 31 and February 1, 1916, fall quite out 

 of the regularity of the series. The conditions involving the indi- 

 vidual gaits are apparently too complex for a simple analysis, and only 

 general impressions can be obtained from the measurements. 



Table 42 also shows the average step-lift per step for E. D. B. with 

 change in the average speeds. Here, as in the case of the total step- 

 lift per meter distance, there is an absence of uniformity in the amount 

 of increase in the step-lift, though the increase is progressive in each 

 instance. 



ENERGY INCREMENT DUE TO WORK OF STEP-LIFT. 



By multiplying the step-lift as given in meters by the body-weight 

 of the subject, it is possible to obtain the kilogrammeters of work done 

 due to this elevation of the body. 1 From this the heat-output per 

 kilogrammeter of step-lift has been computed. (See column / of 



J It is most important to note that the effort of sustaining and lowering the body is entirely dis- 

 regarded in this calculation. 



