STEP-LIFT IN GRADE WALKING. 243 



these are the only results which are at all comparable with data 

 obtained in the earlier part of the series, when the subject was un- 

 trained. These low-grade experiments were, however, so few in num- 

 ber and, particularly, the total amount of work was so small, being 

 in all cases under 300 kg. m. per minute, that the data do not lend them- 

 selves to the critical discussion of the effect of training upon the energy 

 cost per kilogrammeter of work done in walking up-grade. 



STEP-LIFT DURING GRADE WALKING. 



The measurement of the step-lift during horizontal walking is com- 

 paratively simple as determined by the revolution of the work-adder 

 wheel, supplemented and controlled at times by the kymograph tracings 

 of the spring pointer of Dr. C. Tigerstedt. 1 (See p. 30.) The results 

 of these measurements have been discussed in an earlier section. (See 

 p. 155.) 



An attempt was made to measure the step-lift in grade walking by 

 the method used in the horizontal-walking experiments. There is, 

 however, a decidedly different type of step-lift in grade walking as 

 compared to that in walking on a level, for in grade walking the weight 

 is of necessity thrown more on the toes than in walking on a horizontal 

 plane and the center of gravity must be farther forward. In the grade- 

 walking experiments the body continually moved up an inclined plane 

 (the treadmill belt), which, to be sure, was continually passing by the 

 body of the subject. Was any of the movement recorded as step-lift 

 actually due to the "grade-lift" of the body, or was the record an un- 

 contaminated measure of the particular type of step-lift necessarily 

 accompanying grade walking? It was considered that the position 

 of the subject on the treadmill was so closely determined by the mouth- 

 piece and the fork of the step-lift recorder which rested on his shoulder 

 (see fig. 1, p. 19) that he could alter his relative position on the tread- 

 mill but little. This supposition has been confirmed by the photo- 

 graphic tests previously described on page 31. It is recognized, how- 

 ever, that possibilities of error in these measurements are present, 

 as was the case with the measurements for walking on a level. 



As pointed out in the description of the technique (p. 33), the manner 

 of measuring the step-lift in these experiments is fairly open to criti- 

 cism as to the position of the fork. (See fig. 1, p. 19.) After the 

 preparation of this manuscript was nearly completed, it seemed 

 desirable to make tests to note the influence, if any, of a change in 

 position of the fork with relation to the plane upon which the subject 

 walks. 2 Consequently, the mill was set at a 30 per cent grade and the 

 fork was placed in a position parallel to the belt of the mill. Under 



1 C. Tigerstedt, Skand. Arch. f. Physiol., 1913, 30, p. 299. 



2 The author wishes to acknowledge his indebtedness to Dr. F. G. Benedict, who carried out 

 these experiments at a time when he himself was unable to co-operate. 



