CONDITIONS OF STRESS IN UNDERSEA WARFARE 



425 



logical indicators such as metabolism, (b) 

 by subjective criteria such as ratings of 

 "satisfyingness" of work or feehng of fatigue, 

 and (c) by measurements of performance or 

 output of work. In the consideration of 

 stress we are concerned with effects of all 

 three types. Yet, if we may be guided by 

 experience in attempts at the study of fa- 

 tigue, we need expect no close correspondence 

 among measures of these different aspects of 

 stress even when obtained simultaneously on 

 the same subject. This need not mean that 

 the different measures are unreliable, but 

 only that these different aspects of human 

 function are not necessarily closely related 

 and proportional. 



The mobilization of the complex phys- 

 iological organism for varying degrees of 

 activity not too remotely resembles the war- 

 time mobilization of a nation for an offen- 

 sive. Not merely the striking arm at the 

 front, but the entire energy and material 

 producing resources of even remote parts, 

 are marshalled to meet over-all demand. 

 Activity in one part may support that in 

 another — and no less may seriously interfere 

 with that in another. This is strikingly illus- 

 trated by the rising patterns of tension which 

 develop with increasing intensity of activity 

 and motivation. The amount of work done 

 may thereby first increase as the result of the 

 greater effort, and later decrease (40, 95). 



The ideal state of rest is probably one of 

 minimal muscular tension or maximum re- 

 laxation (68). The ideal waking, alert, erect 

 position, on the other hand, %vith shifting 

 position of the head involves complex pat- 

 terns of automatically maintained tensions 

 or "tone" as have been so beautifully demon- 

 strated by Magnus and de Kleijn (80) and 

 reviewed by Fulton (45, 64). Such tensions 

 involve not merely efferent neural discharge 

 into the musculature, but also afferent pro- 

 prioceptive and other discharge back into the 

 central nervous system, thereby providing a 

 circular self-perpetuating background (22) of 

 activity. Upon this background, as by a 



finger painter, shifting concentrations of the 

 "postural substrate'' (42) sketch the pattern of 

 response. The existence of a certain amount 

 of prior tension or "postural substrate" in 

 the system appears to be essential for effec- 

 tive adjustive activity. 



Along with this elevation of postural tone 

 there occurs a general mobilization of various 

 preparatory and facihtative (21) organic 

 processes, notable among which are changes 

 in blood pressure and palmar sweating. The 

 latter activity has proved of particular value 

 as an index of muscular activity (56, 100), 

 alertness, and general mobihzation of the 

 organism (32). It will be referred to later 

 in discussion of test procedures. 



But whereas increases of background ten- 

 sion may, within moderate limits, increase 

 the proficiency of response and explain why 

 various types of stimulation and voluntarily 

 maintained muscular tension may sometimes 

 improve performance (9, 18, 41, 100), a 

 high level of tension in conditions of effort, 

 conflict, and frustration may be reached be- 

 yond which further increments no longer pro- 

 vide further facilitation (18). This is pos- 

 sibly the point at which we begin to think of 

 a situation as involving "stress." It is pos- 

 sibly somewhat beyond this point that we 

 reach the level representing the "PlimsoU 

 mark" (43) of the individual's capacity, 

 beyond which the "load" should not further 

 be increased. In the normal tonic state 

 moderate shifts of tension apparently affect 

 and faciHtate the specific effectors involved in 

 an activity. This may account for facili- 

 tation. With increasing tension and stress 

 as indicated by increased intensity of ac- 

 tivity or by increased exhaustion and fatigue 

 of already active mechanisms it appears that 

 the increase of "tension" with activity may 

 affect not only the specific and appropriate 

 musculature, but larger and less appropriate 

 muscles and groups of muscles as well. The 

 activity may appear to be performed w^ith 

 continued effectiveness, scores on perform- 

 ance may be unchanged or even improved, 



