160 METABOLISM DURING WALKING. 



grouped the average step-lift per day for various speed groups and also 

 the percentage of the heat-output expended due to this step-lift. 

 An inspection of these figures shows no uniform change in the step- 

 lift for a definite speed as the experiments continued, except possibly 

 with the 60 to 68 meter group. In several groups, the percentage of the 

 increment in the heat-output due to the step-lift increased somewhat as 

 time progressed. As has already been seen in other groupings of the 

 results, these figures show that as the speed increased, the step-lift 

 also increased, likewise the percentage of the increment in heat due to 

 the step-lift. 



The above consideration of the step-lift suggests several important 

 lines of study, for if the step-lift involves a minimum of from 10 to 20 

 per cent of the energy required above basal for the work of forward pro- 

 gression, it can readily be seen that a type of gait which would mini- 

 mize the step-lift would tend to decrease this factor. Doubtless the 

 time relations of elevation, sustained suspension, and lowering of the 

 body in typical and atypical gaits would throw much light on this 

 important problem of efficient and economical horizontal walking. 

 That such a study should likewise consider the gait in grade walking 

 is obvious. It is the current practice of experienced mountaineers to 

 alter their gait frequently. 



PHYSIOLOGICAL EFFECTS OF HORIZONTAL WALKING. 



As was done in the standing experiments, records were obtained in 

 these walking experiments of the respiration-rate, pulmonary ventila- 

 tion, pulse-rate, and, in some of the experiments, especially with 

 E. D. B., the body-temperature and blood-pressure. The detailed 

 records are given in the statistical tables 8 to 12, and the daily averages 

 grouped according to speed in table 35. A summary is also given in 

 table 44, in which not only the averages for the speed groups are given, 

 but also the number of experimental periods on which the speed-group 

 data are based, and the increments due to the activity of walking. 

 These increments have been calculated by using as a basal value for 

 each subject the average of the values obtained in his standing experi- 

 ments. (See tables 3 to 7.) 



RESPIRATION-RATE DURING HORIZONTAL WALKING. 



From tables 8 to 12, and 35, and the summary in table 44, it is seen 

 that individual subjects show wide individual differences. For the 

 same subject the increase in the respiration-rate for the moderate 

 speeds of walking was gradual and no larger than the variations in the 

 results for an individual with a definite speed. This applies with 

 E. D. B. up to an average speed of 77.5 meters per minute, but above 

 this speed the respiration-rate increased more rapidly. Thus, the 

 increment above the standing rate was increased 1.9 respirations for 



