394 



Marts Mechanical Efficiency in Work Performance and the Cost 

 of the Movements Involved [Treated Separately). 

 By J. S. Macdonald, Professor of Physiology, Liverpool. 



(Communicated by Prof. C. S. Sherrington, F.E.S. Eeceived May 6, 1914, — 

 received in revised form September 6, 1916.) 



Many of the data contained in this paper have been already published* 

 and submitted to a preliminary process of analysis. From the arrangement 

 then made it was seen that the body-weight exercised two separate, and 

 opposing, influences on the heat production associated with muscular work. 

 A certain steady rate of movement was maintained throughout a long series 

 of experiments, and this was complicated to a different degree, in different 

 groups of experiments, with the performance of different, increasing, amounts 

 of mechanical work. When the heat production was comparatively small, 

 in the case of minimal work performance, it was observed to vary directly 

 with the body-weights of the individual subjects. On the other hand, when 

 larger, this variation was less noticeable, and at a certain stage of increase in 

 the performance of work it was found to have disappeared completely. The 

 fact was very definite, so that in four different groups of experiments 

 arranged in order of reference to rising values of mechanical work the 

 total heat productions measured varied in Group A directly with W 4/3 , in 

 Group B with W 2 '*, in Group C with W 1 ^ and in Group D with W° (Joe. 

 tit., p. 111). No attempt was made at the time, other than contained in a 

 statement of suggestions requiring consideration, to explain this phenomenon, 

 for which course, indeed, an excuse might be found in the labour involved in 

 collecting the information, and the even greater labour of dealing similarly 

 with the very extensive series of measurements underlying the published 

 data. To this problem, then, attention is once more directed in the present 

 paper. In the meantime, these original data have been elaborately and 

 excellently examined by Glazebrook and Dyef in a manner meriting very 

 considerable interest. 



Before once more encountering these facts, an explanation of the chief 

 terms utilised may be of advantage, since the mode of experiment and the 

 actual measurements have of necessity to be kept out of sight, and no 

 opportunities arise therefore for an observation of the way in which the 

 measurements are summed to form the total data displayed. Thus, for 



* " Studies in the Heat-production Associated with Muscular Work. — Preliminary 

 Communication," 'Roy. Soc. Proc.,' B, vol. 87, p. 96 et seq. (1913). 

 t ' Roy. Soc. Proc.,' B, vol. 87, p. 311 et seq. (1914). 



