STEP-LIFT IN GRADE WALKING. 



247 



withstanding the somewhat greater speed in grade walking, the num- 

 ber of steps was not, as a rule, larger than in horizontal walking until 

 a grade of 25 per cent was reached; thereafter the number of steps 

 taken per minute was larger. The step-lift increased very perceptibly 

 with the grade and likewise the step-lift per step. 



In table 68 a similar comparison is made when the average speed for 

 both horizontal and grade walking was 77 meters per minute. In the 

 upper part of the table the data for horizontal walking are more or less 

 representative of duplicate experiments on different days and show no 

 great variation. During the grade walking there was, as with the 

 slower speed, a very perceptible increase in the number of steps with 

 the higher grades, beginning at 20 per cent, although it is again to be 

 noted that in three of the four tests in grade walking the actual rate of 

 walking per minute was somewhat higher than during the horizontal 

 walking. The step-lift increased pronouncedly, as did the step-lift 

 per step. 



TABLE 68. Comparison of step-lift of E. D. B. in horizontal and grade walking 

 at an approximate speed of 77 meters. (Values per minute.) 



It was a special consideration of these latter factors, namely, the step- 

 lift and the step-lift per step, that led us to surmise that the method of 

 measurement of the step-lift indicated in figure 1, i. e., with the fork 

 parallel to the floor and not parallel to the plane of walking, might 

 incorporate in the graphic record a certain component that should 

 properly be ascribed to the grade-lift. This surmise led to the series 

 of experiments reported on page 243, from which the conclusion is drawn 

 from tests made on a single subject (unfortunately not one of the 

 original group) that the step-lift as measured was probably not con- 

 taminated by grade-lift, but, if anything, with the fork parallel to the 

 floor, the apparatus does not record so large oscillations of the shoulders 



