DISCUSSION OF RESULTS. 99 



At the low speed the subject walked 69.3 meters per minute, and took 

 108.2 steps per minute, the average length of the step being 64.0 cm. 

 With an increase in speed we note an increase not only in the number of 

 steps per minute, but likewise in the length of the step, the number 

 of steps per minute for the fast walking being 152.4 and the length of 

 the step 94.8 cm. When we consider the height to which the body was 

 raised, we find that the average height per minute was greatly increased 

 as the speed increased, that obtained at the medium rate being more 

 than twice the value secured with the low speed, i. e., an increase from 

 2.88 meters to 6.69 meters. When the average values obtained at the 

 medium and fast speeds are compared, we find that although the 

 average distance walked per minute increased from 109.0 meters to 

 144.5 meters and the number of steps taken per minute from 130.9 

 to 152.4, the increment in the distance over which the body was raised 

 was but 1.21 meters. 



Of special interest in this connection is the extraordinary influence of 

 the change in locomotion from fast walking to running. The increase 

 in the speed was inconsiderable, being but 3.1 meters per minute. We 

 find, however, that in running the average height to which the body was 

 lifted increased from 7.90 meters to 13.76 meters per minute and the 

 average number of steps from 152.4 to 181.9 per minute, the latter 

 increment not being at all in proportion to the former. On the other 

 hand, the length of the step was decreased in running from 94.8 cm. 

 to 81.1 cm. It is thus apparent that in running the steps were taken 

 much more rapidly and considerably shortened and that the body was 

 raised to a much higher point at each step. 



In any analysis of the mechanics of forward progression, therefore, 

 we should bear in mind the fact that in running the body is actually 

 lifted to nearly twice the height that it is raised during walking. This 

 would of itself involve mechanical work not directly contributory to the 

 work of forward progression and we should therefore expect to find, on 

 this basis alone, that the work of walking would be much more economi- 

 cally done than the work of running. On the other hand, it has been 

 pointed out in connection with the fast walking experiments that the 

 subjects involuntarily, or possibly as the result of previous training, did 

 an excessive amount of muscular work with the arms which likewise 

 was not contributory to the motion of forward progression. If, how- 

 ever, in comparing the values for the heat output per unit of work done 

 in walking and running, we use as a base-line the value obtained with 

 the subject standing and swinging his arms vigorously, we find that the 

 advantage still lies with the walking rather than with the running. 

 Thus, while the heat-output per unit of work with the subject running 

 without food is 0.806 gram-calorie with the standing relaxed base-line, 

 when we use the base-line obtained with the subject swinging his arms 

 the value becomes 0.780 gram-calorie for the 7 periods without food and 



