10 ENERGY TRANSFORMATIONS DURING HORIZONTAL WALKING. 



process of walking. To obtain the best expression of the superimposed 

 energy requirement for forward progression, it is necessary to secure, as 

 nearly as possible, the energy requirement of the subject in a position 

 which involves all of the extraneous muscular movements incidental to 

 the waking condition and in a vertical position. This may be obtained 

 by deducting the metabolism required for the standing position. And 

 yet the earlier researches have been most unsatisfactory in the attempts 

 to measure the metabolism under these conditions. 



With the standing position we again have numerous possible varia- 

 tions. The subject may stand in a completely relaxed position; he 

 may possibly eliminate in a large part the effort of balancing by leaning 

 on a staff or lying back slightly out of the vertical against a support ; or he 

 may stand in a fixed position with rigid muscles, such as that of "atten- 

 tion." We should, theoretically at least, expect to find a considerable 

 difference in the metabolism necessary for these various upright positions. 



Durig has clearly pointed out 1 that there are numerous arguments 

 against assuming that the metabolism while standing in any one of 

 these positions can rightly be deducted from that during walking to 

 obtain the true energy transformation due to the walking, for it is quite 

 possible that certain of the external muscular movements incidental to 

 balancing and sustaining the body in an upright position may be greatly 

 modified, if not indeed dispensed with, in the ordinary motions of for- 

 ward progression. Consequently, one finds that, in previous researches, 

 the base-line used almost universally among physiologists has been the 

 metabolism observed with the subject lying awake without food in the 

 stomach, i. e., in the post-absorptive condition. The assumption is then 

 made that the increment of metabolism during walking over that observed 

 with the subject lying awake is a true measure of the metabolism due to 

 the muscular exercise of moving the body in a horizontal direction. 



UNITS OF MEASUREMENT USED IN WALKING EXPERIMENTS. 



While under ordinary conditions the amount of work performed in 

 any inanimate or animate motions is expressed in terms of foot-pounds, 

 kilogrammeters, or calories, it is obvious that no one of these units can 

 be appropriately employed for indicating the energy transformations 

 during walking. In walking, a given weight is carried through a given 

 distance. To be sure, there is inevitably a slight lifting of the total 

 weight of the body at each step due to the anatomical arrangement of 

 the feet and leg-muscles, but this w r eight is again immediately lowered 

 to the same position, so that, mechanically at least, there is no effective 

 work accomplished. The only external evidence of performance is that 

 a given weight is moved forward a given distance. 



In this discussion we may for the present appropriately eliminate the 

 possible effect of wind resistance produced by the body in walking or the 



1 Durig, Denkschriften d. math.-natur. Klasse d. kaiserl. Akad. d. Wissensch., 1909, 86, p. 267. 



