PLAN OF STUDY. 17 



olism in the grade-walking experiments reported in this publication 

 represented the total energy expended, it was necessary to know both 

 the basal-energy cost and the cost of horizontal walking to obtain the 

 energy cost of the work of elevation. 



Three groups of experiments were therefore carried out: (1) standing 

 experiments, in which determinations were made of the energy ex- 

 pended while the subject was standing quietly without support, these 

 values being taken in the computations as the "rest" requirement; 

 (2) horizontal-walking experiments with measurements of the energy 

 output at different speeds of walking; from these the energy expended 

 in excess of the "rest" requirement was found, and thus the cost of 

 moving 1 kg. of body- weight 1 meter on a level was determined; (3) 

 grade- walking experiments from which the energy expended per kilo- 

 grammeter of vertical lift in excess of the rest and horizontal-walking 

 requirements was calculated for the different grades and speeds with 

 the efficiencies for each condition. 



It was the intention to have the subject walk at certain definite rates 

 hi order that level and grade walking might be compared at the same 

 speeds. Technical difficulties in the precise regulation of the speed of 

 the treadmill made strict duplication too exacting a task in many 

 instances and the results are consequently grouped according to the 

 speeds which fell within limits of 5 meters per minute of each other. 

 The grades were more easily maintained in the range between 2.5 to 

 45 per cent in rates of 5 per cent increase. It would have been desirable 

 to have made both standing and horizontal-walking tests on each day 

 that the grade- walking experiments were made; since, however, it was 

 impossible to make experiments with a sufficient number of periods in 

 each of the three groups, the only alternative was to secure an average 

 value for both the standing and the horizontal- walking experiments. 



The data obtained during the horizontal-walking experiments, besides 

 supplying the energy factor per horizontal kilogrammeter used in com- 

 puting the energy to be deducted from the values for the grade- walking 

 experiments, allow a comparison of this factor with that reported by 

 other investigators, and we believe they present in themselves a sub- 

 stantial addition to our knowledge of the physiology of walking. They 

 also provide additional information as to the effect of the speed of 

 walking upon the energy required per horizontal kilogrammeter, which 

 has been reported to be practically independent of the speed for rates 

 less than 80 meters per minute. 



Another element contributing to the work performed in either 

 horizontal or grade walking in addition to the three factors previously 

 mentioned is the elevation of the center of gravity of the body as it 

 moves forward with each step. This elevation of the body represents 

 a positive and appreciable amount of work. An effort has been made 



