12 



NATURE 



[August 26, 1920 



New Aspects in the Assessment of Physical Fitness. 



By Dr. F. G. Hobson, Department of Pathology, University of Oxford. 



A. Physician in a great city seems to be the mere 

 plaything of Fortune; his degree of reputation ts for 

 the most part casual; they that employ him know not 

 hfs excellence; they that reject him know not his 

 deficience. — Samuel Johnson. 



THESE words might, with truth, have been 

 written of Dr. John Hutchinson, one time 

 physician to the Brompton Hospital for Diseases 

 of the Chest. His earlier years devoted to the 

 study of engineering, he later turned, to medicine, 

 and carried with him into his profession that 

 enthusiasm for the accurate expression of scien- 

 tific data which must have been engendered by 

 his early training. In 1846 he published a paper 

 "On the Capacity of the Lungs and on the Re- 

 spiratory Functions " (i)^, in which he showed 

 that he possessed the inspiration which is ever 

 the mark of true genius, combined with the ability 

 for accurate observation and the patient collection 

 of data. He made the earliest investigations into 

 the physiological effects of " forced breathing " ; 

 by means of a mercurial manometer he examined 

 " expiratory force " ; but interest lies for the 

 special ends of the present subject in the exten- 

 sive series of observations which he made upon 

 the " vital capacity "^ of more than 3000 persons 

 covering a wide range of body size, occupation, 

 and mode of life. 



Dr. Hutchinson claimed that he had shown that 

 "vital capacity" increases in simple arithmetical 

 progression with increasing height, and believed 

 that he had disproved any relationship between 

 "vital capacity" and body weight, trunk length, 

 or circumference of the chest. The fact that his 

 conclusions might be open to criticism, and that 

 the fundamental principles underlying his investi- 

 gation might yet have eluded his grasp, was 

 present in his mind, and he concluded his treatise 

 with the following remarkable sentences, which 

 could well be taken as a model by any scientific 

 worker : — 



The matter of this communication is founded upon 

 a vast number of facts— immutable truths which are 

 infinitely beyond my comprehension. The deductions 

 which I have ventured to draw therefrom I wish to 

 advance with modesty, because time, with its muta- 

 tions, may so unfold science as to crush these deduc- 

 tions and demonstrate them as unsound. 



Nevertheless, the facts themselves can never alter 

 nor deviate in their bearing upon respiration, one of 

 the most important functions of the animal economy. 



This prediction has, with the passage of time, 

 been fulfilled. 



Prof. G. Dreyer, of Oxford University, has 

 made an extensive re-investigation of the whole 

 subject, drawing upon Hutchinson's data as well 

 as upon his own records. In a brilliant analysis 



1 The figures in brackets refer to the Bibliography at the end of the 



2 The term " vital capacity " is used to indicate the maximum amount of 

 air the individual is able to expel from his lungs, by voluntary effort, after 

 the deepest possible inspiration. 



of this considerable body of observations, he has 

 conclusively proved the existence of physiological 

 laws which escaped the mind of the pioneer 

 Hutchinson. On practically every point do these 

 laws refute the conclusions reached by 

 Hutchinson. 



Prof. Dreyer (2) has shown that definite rela- 

 tionships do exist between " vital capacity " and 

 body surface, body weight, trunk length, and 

 the circumference of the chest, while no true re- 

 lationship can be traced when "vital capacity " 

 is regarded as a simple function of the standing 

 height, as claimed by Hutchinson. 



Hutchinson's misconception of the facts may be 

 attributed in part to faulty mathematical analysis, 

 in part to the fact that his observations were 

 made upon subjects covering an insufhciently wide 

 range of weight and size. It is obvious that 

 physiological laws, if such exist, must be applic- 

 able over the entire period of growth of the indi- 

 vidual, and must be inadequate if they can be 

 established only over a limited range of varia- 

 tions of sex, age, stature, body weight, etc. 



The scientific world is now familiar with the 

 conception that certain physical, physiological, and 

 anatomical attributes of the living organism are 

 functions of the surface, and not of the volume, 

 of that organism. Heat loss offers possibly the 

 most familiar example, being relatively greater 

 for the small body than for the large, by virtue 

 of the relatively greater surface area presented 

 by the small body for a given volume. 



How can the surface of an animal be deter- 

 mined? It is simply necessary in this brief article 

 to state that the surface can be determined in- 

 directly from the body weight, of which it is a 

 constant function. For justification of this pro- 

 cedure reference should be made to the original 

 articles which describe the methods by which this 

 relationship was determined (3 and 4). 



Prof. Dreyer has in recent years shown that 

 the blood volume (4), the cross-section of the 

 aorta (5), and the cross-sectiqn of the trachea (6) 

 are " surface functions " of the warm-blooded 

 mammals, and not simply related to the body 

 weight, as has often been maintained. It comes, 

 therefore, as no surprise when he finds that " vital 

 capacity" is also a "surface function," since this 

 must represent, in one direction, the limit of the 

 capacity possessed by the organism for oxygenat- 

 ing its blood and discharging the waste products 

 of its metabolism, and consequently be a physio- 

 logical expression of one most important aspect 

 of respiration. It follows that this measurement 

 gives us an index: of the "vitality" of the or- 

 ganism, i.e. its ability to meet the various strains 

 and stresses of its life. 



If the "vital capacity" is a "surface function," 

 there is the further difficulty to be faced : What 

 (Continued on p. 829.) 



NO. 2652, VOL. 105] 



