A study of methods of recuperation from impairment of performance as a result of previous activity

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A STUDY OF METHODS OF RECUPERATION FRCM IMPAIRMENT OF PERFORMANCE AS A RESULT OF PREVIOUS ACTIVITY

A D is s e r ta tio n P re se n ted to th e F a c u lty o f th e G raduate School The U n iv e rs ity o f S o uthern C a lif o r n ia

In P a r t i a l F u lf illm e n t o f th e Requirem ents f o r th e Degree D octor o f Philosophy

by E liz a b e th M« Prange June 1950

UMI Number: DP29689

All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion.

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This dissertation, written by ............. ELIZ1BETH..1L..EHANGE.....................................

under the guidance of h.^r— Faculty Committee on Studies, and appr ov ed by all its members, has bee*n presented to and accepted by the Council on Graduate Study and Research, in partial ful­ fillment of requirements for the degree of D O C T O R OF P H I L O S O P H Y

1ean

Date.

AUGUST _.!95Q

Committee on Studies

\trman

ii

TABIE OF CONTENTS CHAPTER I.

PAGE

INTRODUCTION......................................................................... The p r o b l e m ......................................................................... * S tatem en t o f th e p r o b le m ............................... ....... O rg a n iz atio n o f rem ainder o f th e d i s s e r t a t i o n

II.

REVIEW OF LITERATURE..................... F a tig u e and im pairm ent •

1 2 2 3 4

.......................................

5

• ..................

5

P sy ch o lo g ists* c o n c e p t ...........................................

8

P h y s io lo g ists* concept ♦ • . .

The s p e c ia l problem o f f l i g h t f a t i g u e . . . . .

10

Summary o f v iew p o in ts on f a t i g u e .....................• •

13

S tu d ie s o f th e re c o v e ry p e rio d * • • • • • • •

14

P hysiology o f rec o v e ry from w o r k .............. .......

14

S tu d ie s o f re c u p e r a tiv e a id s •• • • • • • •

16

E f f e c t o f e x e rc is e and re c o v e ry upon c e r t a i n p h y s io lo g io a l m easures

.....................

27

The use o f ergographs f o r s tu d ie s o f f a tig u e and re c o v e ry • • • • « . . .................................. III.

METHODS AND PROCEDURES

31

...................................

34

The p u rs u it-m e te r e rg o g rap h ...................................

34

The end p o in t o f w o r k ................................... ........

36

R ecu p e rativ e m e a s u r e s ...........................................

37

Measurements t a k e n ....................................................

38

iii

CHAPTER

XV.

V.

V I.

PAGE S u b je c ts . . . . . . . . . . . . . . . . . . .

39

In d o c tr in a tio n • • • • • . • • • • • • • • • •

39

E xperim ental procedure • • • • • • • • • • • «

40

Order o f experim ents • • . • • • • . . . . • •

42

ANALYSIS OF DATA.......................... . ........................« . . .

43

The a n a ly s is o f v a ria n c e t e c h n i q u e .....................

43

A n a ly sis of work tim e . • • • • • • • • • • • •

44

A n a ly sis o f p h y s io lo g ic a l d a ta • • • • • • • •

47

C o r re la tio n Work I and Work I I .....................

50

INTERPRETATION AND DISCUSSION OF RESULTS..................

51

Work P erio d I I • • • • • • • • • • • • • • • •

53

P h y s io lo g ic a l m easures • • • • • • • • • • • •

54

S u b je c tiv e comments

55

. • • • • • • • • • • • •

SUMMARY AND CONCLUSIONS..................... C onclusions

60

• • • • • • • • • • • • • . • • • •

63

Im p lic a tio n s f o r f u r t h e r s tu d y . . • • • • • • •

64

BIBLIOGRAPHY..........................................................................................

66

APPENDIX...................................................................................................

74

iv

LIST OP TABLES table:

page

I

AGE* HEIGHT, WEIGHT.....................................................

74

II

SITTING (1) RECUPERATION.............................................

75

MILD EXERCISE

76

III IV V

COLD PACK

................................................. .......................................

77

HOT SHOWER..........................................................................

78

WHISKEY............................................................

79

V II

SITTING ( S ) ......................................................................

80

V III

MEANS, WORK I AND I I . ................................................

81

VI

CHAPTER I

INTRODUCTION Tasks which a r e f a tig u in g and which can n o t b e made e a s ie r b y a d ju stm en ts i n work r a t e o r lo a d a r e o f te n arra n g ed i n m u ltip le work p e rio d s se p a ra te d by p e rio d s o f r e s t * some re c o v e ry from f a t i g u e i s made*

During th e p e rio d s o f r e s t The amount o f re c o v e ry d u rin g

th e r e s t p e rio d i s a f a c t o r i n th e perform ance i n th e subseq u en t work p erio d s*

Thus, procedu res w hich in c re a s e th e amount o f re c o v ery

would d i r e c t l y improve th e perform ance o f th e subsequent work*

Fur­

th erm o re, th e cum ulative e f f e c t o f such re d u c tio n s i n p o st-e x p o su re i n t e n s i t y and d u ra tio n o f f a tig u e may w e ll red u c e d e t e r io r a ti o n o f v i t a l fu n c tio n s observed i n men i n s t r e s s f u l occupations* M ilita r y f ly in g m issio n s f r e q u e n tly fo llo w th e p a tt e r n o f a l ­ te r n a tin g s t r e s s and r e s t*

P erio d s o f f l i g h t may be a lt e r n a t e d w ith

p e rio d s o f r e s t , d u rin g which tim e th e a i r c r a f t i s on th e ground f o r r e f u e l i n g , rearm ing o r re lo a d in g *

/While th e a i r c r a f t i s on th e ground,

th e f l y e r has th e o p p o rtu n ity o f g a in in g some m easure o f reo o v e ry from th e f a t i g u e o f th e p rev io u s f l i g h t *

G re ater re d u c tio n o f f a tig u e

i n such s i t u a t i o n s may in c re a s e th e f ly e r * s to le r a n c e t o su c c e ss iv e s t r e s s f u l m is s io n s , red u c e f ly in g a c c id e n t r a t e s and c o n tr ib u te to th e p ro lo n g a tio n o f a c t iv e f ly in g c a re e rs * The q u e s tio n o f th e p ro p er c a re o f th e f l y e r betw een f l i g h t s i s o f g r e a t concern to t h e f l i g h t su rg e o n .

S e v e ra l d i f f e r e n t

p ro ced u res have b e en su g g ested t o h a s te n th e f ly e r * s reco v ery from f a t i g u e , and a few o f them have been a d m in istere d *

An o b je c tiv e a s ­

sessm ent o f th e s e p rocedures i n term s o f improvement o f perform ance i n su b seq uent f l i g h t ta s k s has n o t been made* The o b je c tiv e assessm en t o f s e v e ra l v a r i e t i e s o f re c u p e ra tiv e pro ced u res o f p o t e n t i a l u se by f l y e r s i n m il i ta r y a i r c r a f t i s th e su b j e o t o f th e stu d y r e p o r te d i n t h i s paper*

THE PROBLEM S ta te m en t o f th e problem .

The purpose o f t h i s in v e s tig a tio n was

to d i f f e r e n t i a t e betw een v a rio u s re c u p e ra tiv e procedures a s to t h e i r e f f e c tiv e n e s s i n f a c i l i t a t i n g re c o v e ry from s t r e s s r e s u l t i n g from a simu­ la te d f l i g h t task * There w ere th r e e p rim ary a s p e c ts of th e in v e s ti g a t i o n , each o f which c o n tr ib u te s t o th e stu d y o f th e effectiv en e ss o f th e re c u p e ra tiv e procedures

( l ) t o d e sig n and c o n s tru c t a h a p p a ra tu s which would simu­

l a t e some o f th e ' components p r e s e n t i n th e o p e ra tio n o f a i r c r a f t , such as c o o rd in a tio n , v is u a l re s p o n s e , d e c is io n and submaximal m uscular e f ­ f o r t ; (2) to determ in e an end p o in t o f measurement f o r each t a s k s in c e th e s t r e s s e x p erien ced by p i l o t s i s acknowledged t o b e a s t a t e le s s th a n p h y s ic a l e x h a u stio n ; and (3) t o determ ine th e r e l a t i v e re c u p e ra tiv e e f ­ f e c t s o f c e r t a i n p ro ced u res w hich m ight b e used by f l y e r s o f m i l i t a r y a i r c r a f t i n th e b r i e f p e rio d s betw een su o o e ssiv e t a s k s .

ORGANIZATION OF REMAINDER OF TEE DISSERTATION The rem ainder o f th e d i s s e r t a t i o n i s o rganized i n a n e f f o r t t o a c q u a in t th e re a d e r w ith l i t e r a t u r e p e r tin e n t to th e problem (G hapter I I ) t o p r e s e n t a sy ste m atic d is c u s s io n o f th e methods and pro ced u res used (C hapter I I I ) ; and to convey a c l e a r u n d e rstan d in g o f th e a n a l y ti c a l tre a tm e n t o f th e d a ta w ith ensuing r e s u l t s (C hapter IV)•

A d is c u s s io n

and i n t e r p r e t a t i o n o f r e s u l t s o b ta in e d fo llo w s i n C hapter V* A summary, co n clu sio n s and recommendations f o r f u r t h e r stu d y appear i n C hapter V I. Complete t a b l e s o f d a ta a r e found in th e Appendix.

4

CHAPTER I I REVIEW OF LITERATURE *

A review o f s c i e n t i f i c l i t e r a t u r e re v e a le d much re s e a rc h on mus­

c u la r work perform ed i n response to e x te r n a l s t i m u l i .

These re s e a rc h

w orkers w ere concerned p rim a rily w ith maximum e f f o r t* i t s e f f e c t on th e human organism and th e measurement o f changes which occur when work ceases*

L itb le and in c o n c lu siv e evidenoe a p p ea rs i n th e l i t e r a t u r e con­

c ern in g th e e f f e c t s o f v a rio u s ag en ts upon t h e re c o v e ry from prev io u s a c tiv ity *

E ffe c ts o f r e c u p e r a tiv e a id s * when mentioned* have been in ­

c id e n ta l t o th e re s e a rc h * th e prim ary concern having b een w ith th e adap­ t a t i o n o f th e organism to a l t e r a t i o n o f hom eostasis* F u r th e r , th o se s tu d ie s most p re v a le n t i n th e l i t e r a t u r e concerned w ith im pairm ent o f perform ance w ere focused upon sm a ll m uscle groups and th e **lo c a liz e d f a t i g u e 11 syndrome.

R ot u n t i l th e l a s t decade has a t t e n ­

t i o n b e e n sh a rp ly fo cu sed upon th e g e n e r a l i z e d 1* concept o f im pairm ent and f a tig u e *

In c re a se d p re s su re o f i n d u s t r i a l p ro d u c tio n and th e s t r a i n s

and s t r e s s e s o f war upon members o f th e armed fo rc e s and c i v i l i a n s b ro u g h t f o r t h th e need to stu d y and i n v e s tig a te th e vague and g e n e ra lly unknown a re a o f f a tig u e r e s u l t i n g n o t from maximal p h y s ic a l e f f o r t b u t from th e demands made upon th e organism by an a r r a y o f complex s tim u li. As a r e s u l t o f th e w ar-tim e im petus g iven t o th e s e problem s, a v a r i e ty o f concepts has b een forthcom ing concerning th e n a tu r e o f

5

“f a tig u e 1* and "im p airm en t,1* t h e i r r e l a ti o n s h i p t o eaoh o t h e r , and th e m agnitude o f th e problem s p re s e n te d when an a n a ly s is o f t h e i r components i s attem pted* The review o f th e l i t e r a t u r e which follow s i s n o t in te n d ed to b e an e x h au stiv e stu d y o f th e a re a o f fa tig u e *

R a th e r, i t a ttem p ts t o p o r­

t r a y from s e le c te d s tu d ie s th e scope and -v arie ty o f concepts p r e v a ilin g i n re g a rd to f a tig u e and impairm ent*

In a d d itio n t o th e d is c u s s io n o f

f a t i g u e , a s e c tio n i s p re s e n te d on re c o v e ry from -various ty p es o f im­ p a irm e n t, and s e v e r a l s e c tio n s a r e devoted to p h y s io lo g ic a l m easures t h a t p e r t a in t o o rg an ic resp o n ses t o work s tr e s s *

FATIGUE AND IMPAIRMENT The complex phenomenon o f f a tig u e and im pairm ent co n tin u es to be o f concern t o b o th p h y s io lo g is ts and p sy c h o lo g is ts *

Perhaps th e re a so n

f o r t h i s m a n if e s ta tio n o f concern by b o th groups o f s c i e n t i s t s i s t h a t th e n a tu re o f th e phenomena i s so complex i n scope t h a t i t cannot b e de­ s c rib e d com pletely i n term s o f any s in g le s c i e n t i f i c d i s c i p l i n e , b u t demands th e c o o p e ra tiv e e f f o r t o f s e v e ra l a re a s o f sc ie n c e to u n ra v e l i t s i n t r i o a t e p a tte rn * P h y s io lo g is ts 1 c o n c e p t.

In r e l a t i n g th e com parative f a i l u r e o f

th e e f f o r t s o f th e Harvard F a tig u e la b o ra to ry group to fin d s i g n i f ic a n t o b je c tiv e changes r e s u l t i n g from subnaxim al p h y s ic a l f a t i g u e , Forbes (1943) e x p re ssed th e p o in t o f view t h a t p ro g re ss i n th e s tu d y o f f a tig u e

6

has b een impeded by th e g e n e ra l tendency to c o n sid e r f a t i g u e a s a n en­ t i t y w ith o u t c o n s id e r a tio n o f th e many o b serv ab le kin d s o f fa tig u e *

He

compared th e s t a tu s o f re s e a rc h on f a tig u e to a s im ila r s ta g e i n th e stu d y o f d is e a s e , w hen, in th e H ip p o c ra tic p e rio d , everyone spoke sim ply o f sic k n e ss*

A lthough th e r e a r e no sharp b o u n d a rie s betw een d i f f e r e n t

ty p es o f f a t i g u e , Forbes c l a s s i f i e d i t i n t o th r e e g e n e ra l groupings? ( l ) p h y s ic a l f a t i g u e , t h a t which a r i s e s m ainly from e x te n s iv e u se o f one o r more m u scles; (2) m en tal f a t i g u e , t h a t ty p e o f r e a c tio n w hich i s a k in t o boredom; and (3) nervous f a t i g u e , t h a t which r e s u l t s from c o n s ta n t h u r r y , w orry and g e n e r a lly t r y in g to work t o one *s maximum capaci t y i n a comple x s i t u a t i on* A nother p h y s io lo g is t i n th e same la b o r a to r y , ( D i l l, 1933) ex p ressed a s i m il a r p o in t o f view b y s t a t i n g t h a t f a tig u e i s n o t an e n t i t y b u t *

.

m erely a co n v en ien t word t o d e s c rib e a v a r i e t y o f phenomena*

His ca t e -

g o rie s o f f a tig u e in c lu d e one i n w hich la rg e o rg an ic changes o c c u r, and one i n which such changes a r e absent*

I n a l a t e r p ap er (1943) D i l l de­

f in e d f a tig u e as a s t a t e i n which th e organism has l o s t i t s c a p a c ity t o c a r r y on*

E n larg in g upon t h i s d e f i n i t i o n , he s t a te d t h a t a s a r e s u l t

o f m oderate d egrees o f e x e r tio n c a r r ie d on over a long p e rio d of tim e , f a t i g u e i s com posite i n n a tu r e , i* e * , p a r t l y p h y s ic a l and p a r t l y psy­ c h o lo g ic a l o r m ental*

He c i t e d e x p erien c es w ith o v e r-tim e la b o r d u rin g

th e l a s t w a r, showing t h a t , beyond a re a s o n a b le l i m i t , n o th in g was g ain ed i n o u tp u t by le n g th e n in g th e w ork week*

7

I n a d is c u s s io n o f th e org an ic and n o n -o rg an ic n a tu re o f f a tig u e symptoms, T revor (1942) s t a t e d t h a t t h e o n s e t o f f a tig u e i s e a r l i e s t i n '

—

■”j

■— — —

th e m ind, n e x t i n th e n erv e f i b e r s and f i n a l l y i n t h e m u scle. ,______ !__

™ ___

c l a s s i f i e d f a tig u e ass fa tig u e *

r-__ _______

-T*

H©

( l ) norm al fu n c tio n a l f a tig u e and (2) o rg an ic

The form er i s a k in t o th e s e n s a tio n , g e n e ra l ex p erien ce and

b e h av io r o f an a t h l e t e a f t e r p h y sic a l endeavor*

I t c o n s is ts o f a b re a k ­

down o f th e -whole organism —m ind, nerve p a th s and m u sc le s. p o i n t , he o laim ed , th e r e i s maximal p ro d u c tio n o f energy*

At th is Organic

f a tig u e i s c o n sid e re d t o b e caused by toxem ia, n o t n e c e s s a r ily p re s e n t u n t i l th e t i s s u e s a re b e in g used*

The b re a k i n th e c o n tin u ity o f energy

b e g in s p e r i p h e r a l ly , b u t th e continuous p e rc e p tio n o f uncom fortable s tim u li f i n a l l y f a tig u e s th e mind and r e s u l t s i n i r r i t a b i l i t y *

Trevor

a s s e r te d t h a t by red u cin g th e number o f p e rip h e r a l s t i m u l i , th e s e e f f e c t s oan b e made t o d isa p p ea r*

H© © p la in e d th e cau se o f th e two ty p e s o f

f a tig u e i n term s o f c o o rd in a tio n o f im pulse and w i l l i n th e case o f a t h l e t i c e x h a u stio n , and th e disharmony betw een im pulse end w i l l cau sin g “com plete and u t t e r f a t i g u e 111 i n t h e c a s e o f o rg an ic fa tig u e * H e lle b ra n d t, K arpovich (1 9 4 1 ), Davis (1943), and S ayers (1942), ag reed t h a t f a tig u e may be d e fin e d a s a dim inished c a p a c ity f o r doing e f ­ f e c t iv e work a s a r e s u l t o f p rev io u s a c t i v i t y . Grow (1936) d isa g re e d w ith th e a tte m p ts to d e fin e c a te g o r ie s o f f a tig u e and d e c la re d t h a t f a tig u e should p ro p e rly b e considered a s an e n t i t y a n d , f o r purposes o f s tu d y , a s t r i c t s e p a r a tio n in to nervous and m uscular f a tig u e i s c o n fu sin g .

8

H astin g s (1931) emphasized t h a t th e p h y s io lo g is t m ust n ever “le a v e o u t o f mind th e f a c t t h a t i n some way o r a n o th e r he i s d e a lin g w ith th e whole organism and n o t one p a r t a lo n e *M P s y c h o lo g is ts 1 c o n c e p t.

B a rtle y (1943) made a d i s t i n c t i o n b e ­

tw een th e co n cep ts o f im pairm ent and fa tig u e *

“ One i s n o t f a tig u e d un-

t i l he knows i t ; p r i o r to t h i s , one i s only im p a ire d , th e r e a l i z a t i o n o f which becomes a component o f t h e r e s u l t i n g t o t a l f a tig u e syndrome *“ A ccording to B a r tle y , t h e b a s i s o f f a t i g u e i s c o n f l i c t and f r u s t r a t i on, w hether i t a r i s e s o u t o f organ?n and, phy s io lo g ic a l c o n f l i c t o r o u t of c o n f l i c t w hich-i s.- more d i r e c t l y and im m ediately m o tiv a tio n a l*

He d i f ­

f e r e n t i a t e d betw een a c tio n f a t i g u e and a n ti c i p a ti o n f a tig u e and s ta te d t h a t th e l a t t e r e x p re sse s i t s e l f i n th e w ish to escape th e p r e s e n t o r av o id th e fu tu re *

He l i s t e d a number o f concepts he b e lie v e d to be

erroneous i n many o f th e s tu d ie s of fa tig u e * ”1*

The energy c o n c e p t, w herein f a tig u e i s ta k e n t o b e th e d i r e c t

r e s u l t o f w ork. 2*

The

th e a t t r i b u t e s

tendency to assume f a tig u e to be d e fin a b le i n te r n s o f o f th e stim u lu s s i t u a t i o n ,

such a s lo s s o f s le e p tak e n

f o r g ra n te d a s producing fa tig u e * 3*

The

concept o f g e n e ra l f a tig u e o r th e t r a n s f e r o f f a tig u e

from one s i t u a t i o n to th e o th er*

This i s a f a i l u r e to r e a l i z e f u l l y

t h a t f a tig u e a r i s e s from doing som ething more o r le s s s p e c if ic * 4*

That f a tig u e im p a irs perform ance, and t h a t f a tig u e and im­

p airm en t a r e p ro p o rtio n a l* com pensating system*

This i s a f a i l u r e to se e th e organism a s a

9

5*

That im pairm ent and f a tig u e a r e i d e n t i c a l .

6.

F a ilu r e t o d is tin g u is h betw een f a tig u e and le a rn in g *

7*

F a ilu r e t o d e fin e f a tig u e i n an y th in g o th e r th a n s u b je c tiv e

term s Freeman (1948) o u tlin e d th e phenomenon o f f a tig u e i n term s o f th e in flu e n c e o f th e fo llo w in g p r in c ip le s o f resp o n se decrem ent: 1*

TVequenoy (and re c o v e ry ) o f re s p o n se .

2*

S tre n g th o f th e stim u lu s complex*

5*

C om petition betw een r i v a l re s p o n se s.

4*

T ra n sfe r o f decrem ent betw een r e l a t e d re s p o n s e s .

B a r t l e t t (1943) a tta c k e d p re v io u s f a tig u e s t u d i e s , done p rim a rily on i s o l a t e d o r sm a ll m uscle g ro u p s, on th e b a s i s o f w hat he c a l le d one g r e a t u n v e rifie d g u e ss:

”F a tig u e m ust c o n s is t o f d im in ish ed e f f ic ie n c y

o f s p e c if ic perform ance due to th e r e p e t i t i o n o f t h a t perform ance •** The s i t u a t i o n he advocated f o r d e te rm in in g f a tig u e i s one i n w hich th e con­ s t i t u e n t s o f c o o rd in a te d a c tio n can and do change p la c e s , and where tim ­ in g i s an im p o rta n t element*

F u rth e r, he would p ro v id e i n te r r u p tio n s

and r e s t s Yd t h i n th e procedure t h a t w ere no more uniform th a n a c t i o n s , an d , perhaps m ost im p o rta n t, th e p ro v is io n f o r s tim u li which a re n o t a r e p e t i t i v e su c c e ss io n b u t a f i e l d , an organized group o f s ig n a ls cap ab le o f changing t h e i r i n te r n a l arrangem ent w ith o u t lo s s o f t h e i r i d e n t i t y as an o rg an ized group. S t i l l a n o th e r a t t a c k on th e common c o n cep tio n o f f a t i g u e (H off, 1943) was made on th e grounds t h a t f a tig u e conceived a s a d i r e c t and

10

p ro p o rtio n a l r e s u l t o f work i s lim ite d because i t f a i l s to d e fin e th e s u b je c tiv e a s p e c t s , w hich, acco rd in g to some i n v e s t i g a t o r s , c o n s t it u t e th e e s s e n t i a l f e a tu r e o f fa tig u e *

This i n v e s ti g a t o r upheld h is view­

p o in t by th e advances i n knowledge o f c h em istry o f m uscular c o n tr a c tio n , which i n d ic a te t h a t i t i s in c re a s in g ly d i f f i c u l t t o account f o r f a tig u e on th e b a s i s o f a ccu m u latio n o f l a c t i c a c id o r th e d isap p earan ce o f m uscle glycogen*

S ince th e l a r g e s t c a te g o ry o f f a tig u e i s c h a ra c te riz e d

by th e c le a r absence o f e x c e ssiv e m uscular e f f o r t , th e p sy c h o lo g ic a l f a c to r s o f c o n f l i c t and f r u s t r a t i o n a re c o n sid ere d t o be t h e b a s is f o r fa tig u e *

THE SPECIAL PROBLEM OF FLIGHT FATIGUE In a d is c u s s io n o f f a t i g u e i n p i l o t s , M cFarland (1941) p o in te d o u t th e f a i l u r e t o lo c a te f a tig u e in c e r t a i n t i s s u e s o r organs i n s o lv ­ in g p r a c t i c a l problem s r e l a t e d t o s u b je c tiv e f a tig u e and exhaustion* I t was n o ted t h a t m uscular a c t i v i t y in f l i g h t i s lim ite d and could n ot ex h au st every r e s e r v e s u f f i c i e n t l y t o e x p la in t h e f a t i g u e and e x h a u stio n observed i n airm en*

For t h i s r e a s o n , s e v e r a l e s s e n t i a l v a r ia b le s b e ­

lie v e d t o b e c o n tr ib u tin g f a c t o r s i n a c u te and c h ro n ic p i l o t f a t i g u e were l is te d * 1*

P sy c h o lo g ic a l f a c t o r s —em otional s t r e s s , f ly in g h a z a rd s.

2 m Poor p h y s ic a l c o n d itio n .

3*

E f fe c ts o f a l t i t u d e .

4*

D ie t—e s p e c ia lly im p o rta n t because o f e f f e c t s o f oxygen la c k on d ig e s tio n .

11

5.

E f fe c ts o f a lc o h o l and to b a c c o .

6.

E ffe o ts o f n o ise and v ib r a t io n .

M ille r (1936) b ased h is i n v e s tig a tio n on th e prem ise t h a t f l i g h t f a tig u e i s m ainly th e r e s u l t o f em otional c o n f l i c t o r s t r e s s and may be in flu e n c e d by anoxem ia, autonomy, i r r e g u l a r i t i e s and exposure* s p e c ia l e f f e c t s o f f a tig u e n o ted i n t h i s stu d y w ere:

The

( l ) c ir c u la to r y

ch an g es, nam ely, h y p o ten sio n ; (2) changes i n a d a p tiv e m etabolism ; and (3) changes i n b r a in c o n d u c tiv ity and b e h a v io r p a tte rn s *

The most o u t­

sta n d in g fin d in g i n f l i g h t f a tig u e uncovered by t h i s re s e a rc h was hypo­ te n s io n *

I n a s e r i e s o f over 6,000 f l i g h t p h y s ic a l exam inations of a i r ­

l in e p i l o t s , t h i s c o n d itio n predom inated to such an e x te n t a s to accustom th e in v e s tig a to r s t o d is c o n tin u e th in k in g o f i t as a d is q u a lif y in g f a c t o r e x ce p t i n extrem e oases o r when accompanied by o th e r fin d in g s *

Conclu­

sio n s drawn from t h i s stu d y in d ic a te t h a t o b se rv a tio n s o f g ro ss autonomio nervous d is tu rb a n c e do n o t g iv e a c o rr e c t index o f fa tig u e *

The p resen ce

o f co arse tre m o r s , h e te ro p h o r ia , marked e x a g g e ra tio n o f deep ten d o n r e ­ f le x e s and poor neurom uscular c o n tr o l may be a b s e n t i n fa tig u e *

F u r th e r ,

th e employment o f in tr o s p e c tiv e b e h a v io r is tic psychology does n o t se rv e th e purpose i n e s tim a tin g p sychic f a c to r s o f f a t i g u e b ecause o f th e economic f a c t o r and t h e d is r u p tio n of o p e ra tin g regim e occasioned by en fo rced r e l i e f o f p i l o t p e rso n n e l due t o p h y s ic a l cause* P o rte r (1936) d e fin e d two ty p e s o f f a tig u e which a r e o f d i r e c t concern to th e p i lo t *

He s t a te d t h a t nervous f a tig u e can b e c l a s s i f i e d

a s a p h y s io lo g ic a l phenomenon and i s c h a r a c te riz e d by dim inished a t t e n t i o n

IE d i f f i c u l t y i n c o n c e n tra tio n , slow ness i n r e a c tin g t o sen so ry s tim u li and d i f f i c u l t y i n re a s o n in g , b u t i s never m a n ifeste d i n a manner o b je o tiv e enough to be used a s an index o f d e g re e . t i v e o r p sy c h o lo g ic a l i n n a tu r e .

I n i t i a t i v e f a tig u e i s re c e p ­

P o r te r s ta te d i t i s t h e d i r e c t p a th ­

way by w hich th e environm ent and th e s t a t e s o f mind in flu e n c e work o u tp u t. One method su g g ested i n approaching th e s o lu tio n o f th e problem o f f a t i ­ gue i n f ly in g i s th e g rad u a l e lim in a tio n o f a l l e x c e ssiv e o r u nnecessary s e n s a tio n s o r s tim u li from t h i s new environm ent.

I t i s presumed by th e

i n v e s tig a to r t h a t th e r e would b e much c o n se rv a tio n o f n erv e fo rc e i f a r e d u c tio n i n s t r e s s were p o s s ib l e . A survey (G ray b iel eh a l . , 1944) was c a r r ie d o u t among s tu d e n t p i l o t s a t P ensacola i n an e f f o r t to g a in a b e t t e r u n d e rstan d in g o f f a tig u e a s t h e m ajor lim itin g f a c t o r i n th e t r a i n i n g program .

A lthough

th e survey f a i l e d to dem onstrate th e im portance o f a iy p re d is p o sin g f a c ­ t o r s , a number o f p r e c i p i t a t i n g f a c t o r s i n terras o f s u b je c tiv e resp o n se w ere l i s t e d .

The in v e s tig a to r s concluded t h a t s in c e o v e r-fa tig u e o ccu r­

re d d u rin g th e i n i t i a l p a r t o f th e v a rio u s s ta g e s o f t r a i n i n g , d i f f i ­ c u lty i n a d ju s tin g t o new circu m stan ces was a n im p o rta n t f a c t o r i n fa tig u e .

By a l l e v i a t i n g any one o f th e m ajor p r e c i p i t a t i n g f a c t o r s i n

f a t i g u e , i t was b e lie v e d t h a t th e o n se t o f f a tig u e may be le sse n e d and th e re s e rv e in c re a s e d t o a p o in t where o th e r f a c t o r s , n o t so e a s ily r e ­ m ed iab le , w i l l n o t cause o v e r - f a tig u e . A proposed a re a o f stu d y i n f l i g h t f a tig u e i s th e in v e s tig a tio n o f th e fu n c tio n in g o f g la n d u la r a c t i v i t y (Day and A lle n , 1 9 4 8 ).

This

13

p ro p o sa l -was based upon t h e bro ad en in g concepts o f th e r o le o f i n t e r hormonal r e la tio n s h ip s i n th e m aintenance o f hom eostasis w ith in th e human organism*

A nother approach to t h e problem o f p i l o t f a tig u e i s th e

proposed stu d y o f th e in flu e n c e o f th e a d re n a l o o r t ic a l hormone (Hume, 1948)*

Hume emphasized t h e r o l e o f a d re n a l c o r t i c a l s te r o id s i n im­

p ro v in g c e re b ra l a c t i v i t y under c o n d itio n s o f p h y s io lo g ic a l e x h a u stio n sin c e c e r e b r a l fu n c tio n i s th o u g h t to b e t h e lim itin g f a c t o r i n modern a v ia ti o n .

SUMMARY OF VIEiflFOINTS OH FATIGUE From t h i s a r r a y o f c o n c e p ts , i t becomes in c r e a s in g ly c le a r t h a t th e f a tig u e syndrome i s known b y a v a r i e ty o f names and i s composed o f a v a r i e t y o f e le m e n ts, some o f w hich a r e reco g n ized and some o f which a r e not* Trends a re in d ic a te d b y th e fo llo w in g p o in ts as found i n t h e s c i e n t i f i c l i t e r a t u r e reviewed* 1*

The l a r g e s t c a te g o ry o f f a t i g u e , t h e ty p e m ost commonly r e ­

f e r r e d t o a s g e n e ra l f a t i g u e , i s n o t synonymous w ith p h y s ic a l e x h a u stio n . 2.

Modern l iv in g ap p ears t o demand more o f em otional and psycho­

lo g ic a l s t a b i l i t y th a n i t does p h y s ic a l o u tp u t. 3*

More i n v e s tig a to r s appear t o be approaching t h e problem of

f a t i g u e , w hether d e fin e d a s e n t i t y o r n o n - e n tity , from i t s e f f e c t upon th e whole organism , and, c o n se q u e n tly , a re re c o g n iz in g t h e f a c t t h a t many k in d s o f f a tig u e e x is t*

14

4.

The sp e c ific ity * o f im pairm ent m ust b e re c o g n iz e d sin c e f a t i ­

gue r e s u l t i n g from a c e r t a i n t a s k may* presum ably be a ll e v i a te d when a t ­ t e n t i o n i s fo cused on a n o th e r t a s k or when environm ental c o n d itio n s a r e changed. 5*

Few o b je c tiv e s ig n s make t h e i r appearance p h y s io lo g ic a lly i n

w hat i s commonly r e f e r r e d t o a s g e n e ra l f a t i g u e . 6.

There ap p ea rs to b e a growing concept t h a t t h e p sy c h o lo g ic a l

approaches t o t h e problem h o ld more prom ise i n t h e stu d y o f t h i s pheno­ menon th a n th e p re v io u s p h y s io lo g ic a l approach. 7.

I t has been shown t h a t f l i g h t f a tig u e i s c h a ra c te riz e d by

s p e c i f i c a s p e c ts p e c u lia r o n ly t o fly in g * 8*

I n v e s tig a to r s concerned w ith th e w e lfa re o f f l i g h t p erso n n el

acknowledge th e c o m p le x itie s o f th e f a t i g u e s t a t e , and have in d ic a te d a re a s o f r e s e a r c h w hich h i th e r to have re c e iv e d l i t t l e a t t e n t i o n i n con­ n e c tio n w ith th e p a r t i c u l a r problem o f f l i g h t f a t i g u e .

STUDIES OF THE RECOVERY PERIOD P hysiology o f re c o v e ry from work.

P h y sio lo g ic changes observed

i n re c o v e ry from vigorous a c t i v i t y o r a n a e ro b ic work have re c e iv e d much a tte n tio n *

The re c o v e ry p ro c e ss has b e e n analyzed from many a n g le s , i n ­

clu d in g c ir c u la t o r y changes ( D i l l , 1936; Ogden, 1935), payment o f oxygen d e b t ( H i l l , 1926; S a rg e n t, 1926; B erg, 1948), and changes i n th e blo o d co m position ( F a r r i s , 1947; D i l l , 1936).

Fewer acco u n ts a re found i n th e

l i t e r a t u r e concerning th e re c o v e ry changes fo llo w in g m o d erate, o r

15

submaximal, a c t iv i t y *

One re a so n f o r t h i s may be t h a t th o s e w orkers

who have s tu d ie d th e re c o v e ry phase from t h a t p a r t i c u l a r le v e l o f e x e r­ t i o n have found few er r a d i c a l changes a n d , in some c a s e s , no s i g n i f i c a n t d if f e r e n c e s i n p h y s io lo g ic a l p ro c e s s e s . In one stu d y (B ryan, 1935) th e leu c o cy te co u n t o f e ig h te e n women was ta k e n d u rin g m ild a c t i v i t y and compared w ith th e le u c o c y te co u n t a f t e r one hour o f r e s t*

When th e d a ta w ere co n sid ere d a s a w hole, th e

in v e s tig a to r re p o rte d t h a t th e d if f e r e n c e betw een th e mean o f t h e a c t i ­ v i t y count and th e mean o f th e r e s t oou n t was n o t s t a t i s t i c a l l y s i g n i ­ f ic a n t*

However, when th e c la s s i n te r v a l s were grouped s e p a r a te ly , a l l

groups above th e 6 ,0 0 0 -7 ,0 0 0 group showed a d e f i n i t e and s i g n i f i c a n t ten d en cy f o r mean le u c o c y te count t o be lower a f t e r one hour o f r e s t * Using th e th e rm a l c o n d u c tiv ity method o f gas a n a l y s i s , Berg (1948) found t h a t du rin g re c o v e ry from m oderate e x e rc is e ( s t o o l s te p p in g ) , t h e av erag e carbon d io x id e h a lf -tim e c o n s ta n t ( th e tim e when th e r a t e o f gas exchange i s o n e -h a lf th e amount a t o n s e t o f re c o v e ry ) o f t h i r t y - s i x sub­ j e c t s was 40 p e r c e n t more th a n t h e average oxygen h a lf - tim e c o n stan t* This was in te r p r e te d t o mean t h a t th e r a t e o f payment o f t h e oxygen d e b t i s more ra p id th a n th e e lim in a tio n o f corresponding carbon dioxide* To determ ine th e n a tu re and e x te n t i n tim e o f th e re c o v e ry pro­ c e s s , H i l l and h is co-w orkers (1924-1925) d iv id e d th e stu d y in to t h r e e p a rts :

( l ) e a r ly s ta g e s o f re c o v e ry ; (2 ) l a t e r s ta g e s o f re c o v e ry ;

(3 ) e f f e c t o f p a r t i a l p re s s u re on re c o v e ry p ro ce ss*

V arious ty p es o f

e x e rc is e were used b u t o n ly t h a t w hich was term ed ttf a i r l y m oderate11 e x e rc is e i s c o n sid e re d h ere*

I t was found t h a t a f t e r m oderate,

s h o r t- liv e d e x e r c is e , re c o v ery was r a p i d and p r a c t i c a l l y com plete i n a few m in u te s’ tim e .

F u r th e r , s in c e i n m oderate e x e r c is e , th e contem­

p o ra ry oxygen supply i s n ev er in a d e q u ate and th e l a c t i c a c id i s n ev er a b le t o escape from th e m uscles where i t i s form ed, th e oxygen d e b t, even when th e e x e rc is e was con tin u ed f o r a long tim e , was v e ry sm a ll. R esearch w orkers a t th e H arvard F a tig u e L aboratory (F o rb e s, 1943) sought t o ob serv e w hat p h y s io lo g ic a l changes o ccu rred i n i n d u s t r i a l w orkers a s a r e s u l t o f a long day a t t h e i r jo b s •

By comparing th e s e ob­

s e rv a tio n s w ith what had been e s ta b lis h e d p re v io u s ly i n term s o f norm al v a lu e s o f a l l p h y s io lo g ic a l p ro c e s s e s , n o th in g t h a t could b e m easured was found t o b e changed s i g n i f i c a n t l y . I t i s obvious from th e s tu d ie s p re s e n te d h e re t h a t th e s tu d y o f re c o v e ry from submaximal work i s g r e a t l y impeded by th e absence o f any r e a l o r s i g n i f i c a n t p h y s io lo g ic a l changes a s a r e s u l t o f such a c t i v i t y . Recovery from p h y s ic a l e x h a u stio n i s more c le a r ly observed sin c e t h e r e a r e a c tu a l changes which c an be observed and m easured, b u t t h i s does n o t ap pear t o b e th e case i n th e f a r more common type o f e x e r tio n e x is ­ t e n t i n m ost occu p atio n s o f th e p re s e n t d a y . S tu d ie s o f re c u p e ra tiv e a i d s .

The fo llo w in g r e p o r ts from th e

l i t e r a t u r e g iv e an i n d ic a tio n o f some methods and tre a tm e n t t h a t have been a p p lie d d u rin g th e re c o v e ry phase fo llo w in g a c t i v i t y .

M th o u g h ‘

th e s e a r e a l l r e p o r ts o f re c o v e ry from maximal w ork, th e y a r e p re s e n te d t o e s t a b l i s h some p o in ts o f re fe re n c e a s t o th e e ff e c tiv e n e s s o f c e r t a i n a id s and re c u p e r a tiv e p ro c e d u re s .

The review i s d iv id e d i n to th re e

17

groupings::

(A) ergogenio a i d s , (B) e x te r n a l re c u p e ra tiv e p ro c e d u re s,

and (c) r e s t pauses* (A)

E rgogenic aid s*

H e lle b ra n d t (1947) and co-w orkers

v e s tig a te d th e in flu e n c e o f m echolyl and h ista m in e io n to p h o re s is on r e ­ covery from “a l l - o u t e f f o r t 11 on a f in g e r ergograph#

They re p o rte d t h a t

m echolyl and h ista m in e a lo n e produced r e l i e f from p a in , sw ellin g and s t i f f n e s s , le a v in g th e arm warm and su p p le , b u t n e it h e r a g e n t in c re a s e d th e a b i l i t y t o perform work by s t a t i s t i c a l l y s i g n i f i c a n t am ounts• I n a d is c u s s io n o f tre a tm e n t o f f a t i g u e , Hoff (1943) l i s t e d s e v e r a l a g en ts w hich can be a d m in iste re d acco rd in g t o th e a n a ly s is o f t h e ty p e o f fa tig u e #

I t would a p p e a r, how ever, t h a t i n most c ase s f a t i ­

gue from extrem e p h y s ic a l e x h a u stio n i s im plied* (1)

D ie ta ry : ( a ) Sugar—U seful whenever b lo o d sugar f a l l s t o hypoglycemic le v e ls r e g a r d le s s o f ty p e o f a c t i v i t y o r em otional s t a t e t h a t produced i t* (b) G e la tin —Claimed to p o ssess a n a n t i ­ f a tig u e a c tio n (60 gm# d a i l y ) . Co) V itam ins— In r e p o r ts o f v ita m in B de­ f ic ie n c y f a tig u e i s one o f th e most pronounced symptoms • H off s t a te d f u r t h e r t h a t improvement on a d m in is­ t r a t i o n o f v ita m in s has been noted*

(2) In o rg an ic s a l t s —B oth a l k a l i e s and a c id if y in g a g e n ts have been re p o rte d as b e in g o f a s s i s ­ ta n c e i n d e la y in g th e o n se t o f f a t i g u e . (3 ) P h a rm a c e u tic a ls:

18

(a ) Oxygen. (b ) D i g i t a l i s and co r amine to improve m axi­ mal perform ance o f th e c a rd io v a s c u la r system . (o) C a ffe in e and b e n z e d rin e , b o th o f which a c t on th e nervous system to red u c e th e s e n s a tio n s o f f a t i g u e . (d) C o r tic a l e x tr a c t s o r s tim u la tio n o f th e sy m p ath etic nervous system , which a c t d i r e c t l y on m u scle, on th e c a rd io v a sc u ­ l a r system or on th e le v e l o f b lo o d s u g a r. A ccording t o H enschel (1 9 4 2 ), e x tr a s u p p lie s o f v ita m in s have no in flu e n c e on p h y s ic a l a b i l i t y , r e s i s t a n c e t o f a tig u e o r on th e r a t e o f re c o v ery from se v ere m uscular work*

He f u r t h e r s ta te d t h a t op tim al i n ­

ta k e s o f v a rio u s foods a re n o t f u l l y e s ta b lis h e d . An i n v e s tig a tio n (A ir M a te rie l Command, 1948) on a lk a lin e r e ­ se rv e and re c o v e ry r a t e from e x e rc is e ( s to o l ste p p in g f o r th r e e m in u tes) showed t h a t a f t e r an in c re a s e o f a lk a li n e re s e rv e by in g e s tio n o f sodium b ic a rb o n a te o r sodium a c e t a t e , th e r e was c o n sid e ra b le change i n oxygen and carbon d io x id e rec o v ery speeds*

The observed changes were presumed

t o o ccu r a s a r e s u l t o f th e a c t io n o f t h e sodium b ic a rb o n a te i n in c r e a s ­ in g th e carbon d io x id e c a rry in g c a p a c ity o f t h e blood and a s a r e s u l t , th e carbon d io x id e may be e lim in a te d more r a p id ly from th e body*

I t a ls o

appeared to in c re a s e th e re c o v e ry r a t e o f oxygen consum ption, w hich may be r e l a t e d to changes o f carbon d io x id e te n s io n s i n th e blood*

The i n ­

v e s t ig a to r s p o in te d o u t, however, t h a t th e e f f e c t o f in c re a s e d a lk a li n e r e s e r v e i s s i g n i f i c a n t l y g r e a t e r on carbon d io x id e e lim in a tio n th a n on oxygen consum ption.

19

In a su rv ey o f methods used f o r im proving p h y s ic a l perform ance o f men, H e lle b ra n d t and K arpovich (1941) s ta te d t h a t ergogenic a id s may be used to d e la y th e o n s e t o f e x h a u stio n , t o h a ste n re c u p e r a tio n o r to d u ll aw areness o f fa tig u e *

In any c a s e , th e a g en c ie s which augment

work c a p a c ity by im proving th e c o n d itio n o f th e machine a re th e s a f e s t . Those w hich push a p e rso n beyond norm al lim i ts o f endurance a re p oten ­ t i a l l y dangerous and should be re s e rv e d f o r s t r i c t l y emergency use* Follow ing i s a l i s t o f ergogenic a id s which have been used*

A gain, th e

use o f th e a id s im p lie s tre a tm e n t d ir e c te d by a n a ly s is o f f a t i g u e . (1 ) Doping. (2 ) Emergency r a t i o n s . (3) G a s tric stim u la n ts Meat e x tr a c ts A lco h o lic b ev erag es Gold meal (4 ) Fuel f o r e x e rc is e C arbohydrates F a ts Sugar G e la tin V itam ins A lk a lie s A cids P h arm aceutical su b stan ces Endocrine hormones (B)

E x te rn a l re c u p e ra tiv e p ro c e d u re s .

O bservations w e

made by Edgecombe and B ain (1899) on th e e f f e c t o f v a rio u s ty p e s o f b a th s and massage on th e blo o d p re s s u re o f e le v e n s u b je c ts ra n g in g i n age from tw enty to s i x t y y e ars*

Cold imm ersion b a th s o f p l a i n w a ter r a is e d

20

a r t e r i a l p re s s u re and lowered venous p r e s s u r e .

These changes were a t ­

t r i b u t e d m ainly t o changes" i n p e rip h e r a l r e s i s t a n c e .

P e rc u ssio n added

to c o ld immersion in c re a s e d th e r i s e i n a r t e r i a l p re s s u re a t t r i b u t e d t o a p ro b ab le in c re a s e i n h e a r t o u tp u t.

Hot imm ersion b a th s o f p l a i n

w ater lowered b o th a r t e r i a l p re s s u re and venous p r e s s u r e , th e changes b e in g ro u g h ly p ro p o rtio n a te t o th e in c re a s e i n te m p e ra tu re .

Changes

h ere w ere sa id to be th e r e s u l t o f p e rip h e r a l a r t e r i o l a r d i l a t i o n and a n in c re a s e d c a p a c ity i n v a s c u la r system r e s u l t i n g from t h a t d i l a t i o n . T u rk ish b a th s low ered a r t e r i a l and venous p re s s u re t o a g r e a te r e x te n t th a n t h e p reced in g b a th s .

P u lse r a t e was g r e a t ly in c re a s e d .

A sso c ia te d

w ith p e rip h e ra l v a s c u la r d i l a t i o n , t h e r e was th o u g h t to b e a dim inish ed o u tp u t o f th e h e a r t .

S a lin e b a th s a t room tem p e ra tu re s lowered a r t e r i a l

p re s s u re to a g r e a te r e x te n t th a n p la in w a te r b a th s a t th e same tem p era ­ tu re .

Venous p r e s s u r e , th o u g h low ered, was r a is e d r e l a t i v e t o th e f a U

in a r te r ia l p ressu re .

There was an in d ic a tio n t h a t th e amount o f a r t e r i o ­

l a r r e la x a tio n caused by im m ersion i n warm w ater'becom es p ro g re s s iv e ly g r e a te r w ith th e in c re a s e i n s a lin e m a t e r i a l.

Dry massage lowered

a r t e r i a l p re s su re and r e l a t i v e l y o r a b s o lu te ly r a is e d venous p re s s u re u n le s s th e abdomen was massaged v ig o ro u s ly , i n w hich c a se a r i s e i n a l l p re s s u re s o c c u rre d .

The f a c t o r p rim a rily a f f e c te d by massage was p e r i ­

p h e ra l r e s i s t a n c e .

The r e s u l t was s a id to be due t o p e rip h e r a l r e la x a ­

t i o n and t o d is p e r s a l o f blood accum ulated i n th e .sp lan ch n ic a re a in to system ic c i r c u l a t i o n ,

farm te m p era tu re and massage low ered a r t e r i a l and

r a is e d a b s o lu te venous p re s s u re to a g r e a t e r e x te n t t h a n dry m assage.

21

Using dogs f o r e x p e rim e n ta tio n i n th e stu d y o f th e e f f e c t s o f co ld b a th s on th e in c re a s e o f o x id a tiv e p ro c e s s e s , Burg and L eichsen rin g (1921) found t h a t th e s tim u la tin g e f f e c t o f low te m p e ra tu re on o a ta la s e p ro d u c tio n i n warm-blooded anim als d e crea se d w ith a r i s e i n te m p e ra tu re , d isa p p e a rin g a t room tem perature*

B aths a t 35° C. produced

no in c re a s e i n o x id a tio n in warm-blooded anim als and such b a th s d id n o t in c re a s e c a ta la s e *

The co n clu sio n s drawn from t h i s stu d y m u st, o f c o u rs e ,

be in te r p r e te d w ith in t h e lim i ts o f th e o b s e rv a tio n s , b u t i t i s in c lu ­ ded h e re a s a p o s s ib le avenue f o r f u r t h e r i n v e s tig a tio n w ith re fe re n c e t o human s u b je c ts* H orvath and h is co-w orkers (1949) s tu d ie d evidence o f o rth o ­ s t a t i c hypo ten sio n fo llo w in g h o t or c o ld b a th s *

They found t h a t h o t

b a th s w ere a m ajor c o n trib u tin g f a c t o r in c a u sin g o r t h o s t a t i c h y p o ten sio n upon p a s s iv e a l t e r a t i o n o f p o stu re from th e su p in e to th e e r e c t p o s itio n * The c a u s a tiv e f a c t o r was presum ably th e r e s u l t o f a com bination o f p o o l­ in g o f blood and f l u i d i n th e e x tre m itie s and a f a i l u r e o f th e p re s s o s e n s ib le r e f le x e s to b rin g about th e r e q u i s i t e in c re a s e i n c a rd ia c o u t­ put*

E re o t p o stu re was m ain tain ed w ith g r e a t e r ease and reduced c a r d io ­

v a s c u la r demands fo llo w in g c o ld b a th s (18° C*)*

The in v e s tig a to r s n o te d ,

however, t h a t c ir c u la to r y d is tu rb a n c e s a f t e r th e h o t b a th s were n o t r e ­ v e a le d i n th e su p in e p o s i t io n , only under a d d itio n a l s tr e s s *

The i n ­

fo rm a tiv e elem ent b e a rin g a r e l a t i o n t o th e stu d y o f im pairm ent i s th e s u b s ta n tia tin g f a c t o r o f v a s o d ila tio n w hich a p p a re n tly r e s u l t s from h o t b a th s*

T his f a c t o r may b e o f im portance i n th e stu d y o f re c u p e ra tiv e

p ro c e d u re s•

22

In an e f f o r t to a s c e r t a i n th e speed o f l a c t a t e rem oval fo llo w in g e x e r c is e on a b ic y c le e rg o g ra p h , th r e e s u b je c ts rec o v e re d under t h r e e c o n d itio n s i n d i f f e r e n t experim ents (Thomas and Keys, 1940).

Recovery

p ro ced u res w ere bed r e s t , continuous m ild e x e rc is e and bed r e s t w ith c i r c u l a t i o n i n th e le g s f a c i l i t a t e d by d iath erm y .

R e s u lts o f th e stu d y

showed t h a t i n e le v e n experim ents th e v e lo c ity c o n s ta n t o f l a c t a t e r e ­ moval was 0.0531 a t bed r e s t ; t h a t oontinued m ild e x e r c is e du rin g r e ­ covery produced a n in c re a s e d r a t e o f l a c t a t e rem oval i n two s u b je c ts b u t not in a th ird .

I t was n o ted t h a t th e speed o f l a c t a t e removal was n o t

a sim ple fo n c tio n o f t o t a l c i r c u la t io n i n any o f th e experim ents*

Dia­

therm y produced an in c re a s e d r a t e o f l a c t a t e rem oval i n two s u b je c ts b u t n o t i n a th ir d *

Both m ild e x e rc is e and diatherm y produced a marked

e le v a tio n o f m inute o u tp u t i n a l l s u b je c ts .

T his stu d y se rv e s t o empha­

s iz e th e c o m p lex itie s o f t h e re c o v ery p ro ce ss even when s t r e s s produced i s one o f a p h y s ic a l n a tu r e . O bservations were made on t h e rec o v e ry o f m uscles o f th e f in g e r and elbow f le x o r s fo llo w in g a c o n d itio n o f a b s o lu te f a tig u e (lam b, 1926). R e s t, r a d i a n t h e a t, m assage and galvanism were employed a s re c u p e ra tiv e a g e n ts .

In th e experim ents conducted, th e re c o v e ry from lo c a liz e d ab­

s o lu te f a tig u e a f t e r two m in u te s1 massage, as compared w ith r e s t f o r th e same p e rio d , showed an in c re a s e o f 1 p e r c e n t i n th e amount o f work t h a t could be perform ed.

W ith f i v e minutes* m assage, th e m uscle was

a b le t o perform 18.9 p e r c e n t more work th a n when th e m uscle r e s te d f o r th e same le n g th o f tim e .

R adiant h e a t enabled t h e m uscle t o do

19.1

25

p e r c e n t more th a n r e s t * more th a n r e s t*

Massage enabled th e m uscle to do 2 5 .8 p e r c e n t

Galvanism enabled th e m uscle to do 28*1 p e r c e n t more

th a n r e s t * In a d is c u s s io n o f th e e f f e c t o f m assage, h e a t and e x e rc is e on l o c a l c i r c u l a t i o n , H ew lett (1922) s ta te d t h a t h e a t tended t o in c re a s e t h e amount o f blood i n h e ated t i s s u e * p ro lo n g ed , had th e o p p o site e f f e c t*

C old, i f n o t too in te n s e and to o Contin u e d a p p lic a tio n o f h o t w a te r

t o th e arm in c re a s e d t h e lo c a l r a t e o f blo o d flow from fo u r t o e ig h t tim e s , and continued a p p lic a tio n o f cold caused th e lo c a l r a t e t o f a l l t o o n e -h a lf o r o n e -fo u rth o f t h e o rig in a l*

In g e n e ra l, th e a p p lic a tio n

o f h e a t t o any p o rtio n o f th e p e rip h e ry o f th e body i s p u rp o rte d to cause n o t o nly a lo c a l in c re a s e o f b lo o d flo w , b u t i t appears t o cause an in c r e a s e i n c ir c u l a t i o n i n a l l p o rtio n s o f th e body su rfa c e *

In d i­

c a tio n i s g iv en i n t h i s stu d y t h a t th e a c c e le r a tio n o f b lo o d flow caused b y v o lu n ta ry u se o f l o c a l m uscle depends l e s s upon th e m echanical e f f o r t o f m otion th a n upon th e v o lu n ta ry in n e rv a tio n o f m uscles used*

M assage,

he s t a t e d , i s n o t e q u iv a le n t t o e x e rc is e and does n o t produce marked sw e llin g o f th e arm* The r e c u p e r a tiv e v a lu e o f changes in body p o s tu r e , h o t and c o ld showers and massage w ere s tu d ie d fo llo w in g perform ance on a rowing m achine (Amori, 1955)*

Bach procedure was e v a lu a te d i n term s o f i t s

e f f e c tiv e n e s s i n a id in g m uscular o u tp u t fo llo w in g recovery*

Massage

was found most e f f i c i e n t , c o ld shower ran k ed second and h o t shower t h ir d * Blood p re s s u re d id n o t prove t o be a f a c t o r i n t h e d e te rm in a tio n o f

24

s u p e r io r ity o r one re c u p e ra tiv e procedure over an o th e r*

R ecu p erativ e

e f f ic ie n c y was found t o c o r r e l a t e c lo s e ly w ith body te m p e ra tu re . I t has been re p o rte d t h a t during th e l a s t w ar c o ld h ip b a th s w ere employed i n Germany i n b o th in d u s try and A ir Force to ward o f f th e on­ s e t o f f a tig u e and t o h a s te n re c o v e ry from i t ( T u t t l e , 1949).

In o rd er

to g a in f u r t h e r in fo rm a tio n r e l a t i v e to b e n e f i c i a l e f f e c t s o f l o c a l ap­ p l i c a t i o n o f c o ld on re c o v e ry from f a t i g u e , T u tt l e , Happ and W ilson (1949) a p p lie d i c e packs t o th e abdomens o f s u b je o ts d u rin g a ten -m in u te r e s t betw een two p e rio d s o f w ork.

The d a ta o b ta in e d re v e a le d t h a t i n

ev ery case th e d ro p -o f f i n work fo llo w in g a r e s t p e rio d w ith an abdom inal pack was s i g n i f i c a n t l y le s s th a n when th e ic e pack was om itted*

I t was

a ls o observed t h a t , f o r th e most p a r t , th e a p p lic a tio n o f abdom inal ic e packs betw een b o u ts o f stre n u o u s e x e rc is e a ll e v i a te d t h e symptoms o f e x h a u stio n , such a s d iz z in e s s , nausea and m uscular w eakness. Krusen (1941) s t a te d t h a t lo c a l a p p lic a tio n s o f c o ld a r e in d ic a te d c h ie f ly when v a s o c o n s tr ic tio n i s d e s i r e d .

He c o n tra s te d th e observa­

t i o n s of two i n v e s t i g a t o r s , one o f whom found t h a t c o ld a p p lie d e x te r n a lly to th e abdom inal w a ll caused a d e c rea se i n tem p e ra tu re o f subsequent and n e ig h b o rin g i n t r a p e r i t o n e a l t i s s u e s .

The o th e r in v e s tig a to r found

t h a t upon a p p lic a tio n o f c o ld t o th e abdomen o f an obese perso n f o r n in e ty m in u te s, th e te m p e ra tu re o f th e s k in f e l l to 42*8° F . , b u t th e tem p era tu re o f abdom inal m uscles a t a d e p th o f 50 mm. f e l l o nly from o o 9 9 .7 F . t o 96*8 F« i n th e same le n g th o f tim e .

25

(c)

R e st pauses*

A. number o f re s e a r c h w orkers have i n ­

v e s tig a te d th e v a lu e o f v a rio u s d u ra tio n s o f r e s t when i n s e r te d betw een work p e rio d s*

The p e rio d s o f r e s t , a s s tu d ie d i n th e l i t e r a t u r e r e ­

viewed below , a r e n o t accompanied by any re c u p e r a tiv e a id o th e r th a n t h e c e s s a tio n o f work i t s e l f . One o f th e e a r l i e s t in v e s tig a tio n s o f r e s t pauses and t h e i r a b i l i t y to f a c i l i t a t e work o u tp u t was conducted by Maggiora (1890).

He

s tu d ie d th e r e s t pause n e c e s s a ry betw een p e rio d s o f work to m a in ta in o u t­ p u t c o n s ta n t th ro u g h o u t th e day* hours

A ccording t o him , a r e s t pause o f two

i s ^ s u f f i c i e n t t o p rev e n t th e accum ulation o f f a tig u e and t o se ­

c u re from t h e m uscle ( f le x o r m uscles o f

th e m iddle f in g e r )

i n th e e v en in g ,

as w e ll a s i n th e m orning, th e q u a n tity o f m echanical work w hich i t i s cap ab le o f producing under c o n d itio n s of com plete r e s t . ”

He a ls o found

t h a t w h ile t h i s optimum r e s t pause i s c o n s ta n t f o r any one p e rs o n , i t i s n o t o f th e same d u ra tio n f o r a ll* W eiler (1927) used a s p rin g dynamometer t o s tu d y t h e amount of re c o v e ry i n m uscles in v o lv ed i n g rasp in g a f t e r a r e s t p e rio d o f two m inutes*

He concluded t h a t th e tw o-m inute r e s t p e rio d produced an i n ­

c re a s e i n o u tp u t o f 24*8 p er c e n t i n th e second work p e rio d * Mosso (1 9 2 7 ), u sin g a f i n g e r e rg o g ra p h , s tu d ie d th e work o u tp u t fo llo w in g two d i f f e r e n t c o n d itio n s*

The re c o rd o f t h e f i r s t w ork s e r i e s

fo llo w in g bed r e s t was compared w ith work o u tp u t o f th e second s e r ie s fo llo w in g a fo u r-h o u r m ountain c limb •

He found t h e t o t a l o u tp u t o f

work t o be a p p ro x im ate ly t h e same i n th e tsro s e r i e s a lth o u g h t h e maximal

26

o u tp u t i n th e second s e r i e s was a tta in e d l a t e r th an t h e maximal o u tp u t i n th e f i r s t s e r ie s * Crawley (1926) stu d ie d t h e problem o f re c o v e ry from work p e r ­ formed by th e arm and le g i n w e ig h t l i f t i n g * betw een two sta n d a rd p e rio d s o f work*

A .r e s t p e rio d was in s e r te d

R e s u lts o b ta in e d show t h a t th e

amount o f work done i n t h e work p e rio d seemed g r e a te r i n p ro p o rtio n f o r th e arm th a n f o r th e l e g , th e same tim e b e in g allow ed f o r re c u p e ra tio n * Recovery from work was g r e a t e r a f t e r a fo u r-m in u te r e s t p e rio d th a n a f t e r a tw o-m inute r e s t i n t e r v a l .

In g e n e r a l, more w ork was accom plished i n

th e seoond work p e r io d , which follow ed a f i r s t p e rio d o f heavy w eight perform ance*

C o n v ersely , t h e second work p e rio d fo llo w in g t h e p e rf o r ­

mance w ith th e l i g h t w e i g h t s showed le s s work accom plished* In an i n v e s tig a tio n based upon t h e f a t i g u e o f th e f le x o r m uscles o f th e index f in g e r (Broca and R ic h e t, 1927), t h e w orkers concluded t h a t : w ith l i g h t lo ad s r e s t pauses a r e a n u isa n c e , w ith average lo ad s r e s t pauses a re i n d i f f e r e n t , and w ith heavy lo ad s r e s t pauses a r e fa v o ra b le to p ro ­ d u c tio n o f work* W a llric h and co-w orkers (1 9 2 0 ), u sin g a b ic y c le erg o m eter, found t h a t e f f ic ie n c y i s in c re a s e d by s p e l ls o f r e s t when work i s heavy, b u t t h a t when work i s l i g h t , s p e l l s o f r e s t d e c re a se e f f ic ie n c y . In an a n a ly s is o f problem s in i n d u s t r i a l p h y sio lo g y , Simonson (1947) s ta te d t h a t th e le n g th and d i s t r i b u t i o n o f r e s t pauses w i l l de­ pend on:

( l ) th e deg ree o f f a tig u e r e f l e c t e d i n th e e f f e c t o f work on

p h y s io lo g ic a l p ro c e s s e s ; (2) t h e speed o f re c o v e ry ; and (3) th e r a t e o f lo s s o f a d a p ta tio n *

27

E ffe c t o f e x e rc is e and re c o v e ry upon c e r t a i n p h y s io lo g ic a l m ea su re s« (A) H eart r a t e .

In a d is c u s s io n o f m echanotherapy,

Krusen (1941) s t a te d t h a t , w ith v o lu n ta ry m uscular c o n tr a c tio n , th e c a rd ia c r a t e depends m ain ly on th e p h y s ic a l c o n d itio n o f th e s u b je c t and th e s e v e r ity o f th e e x e r c is e . R esearch has b een conducted on th e r e l a t i o n o f v a s o d ila tio n t o th e d u ra tio n o f ta c h y c a rd ia fo llo w in g s h o rt ex h au stin g e x e ro is e .

In one

such i n v e s tig a tio n Herxheimer (1948) found t h a t by bandaging th e le g s and arms im m ediately a f t e r e x e r c is e , th e h e a r t r a t e re c o v ery was f a s t e r . Measurement o f th e b lood volume i n th e le g s a f t e r e x e rc is e was in c re a s e d g r e a t l y , on t h e av erag e 275 c c .

The i n v e s tig a to r s t a t e d t h a t such

v a s o d ila tio n occurs i n rec o v ery from sev ere e x e rc is e and t h e amount of blo o d pooled under such c o n d itio n s probably v a r ie s g r e a t l y .

The stu d y

showed t h a t com pression o f th e p e rip h e ra l v a s c u la r bed a b o lish e d th e ex­ c e s s iv e d u r a tio n of t h e ta c h y c a rd ia j however, t h i s is n o t i n f e r r e d as d i r e c t evidence f o r th e p e rs is te n c e o f p e rip h e r a l v a s o d ila ta tio n a n d , th e r e f o r e , does n o t d em onstrate t h a t t h i s i s th e cause of t h e ta c h y ­ c a r d ia . C o tto n and D i l l (1935) stu d ie d th e r e l a t i o n betw een t h e h e a r t r a t e d u rin g e x e ro is e and t h a t im m ediately fo llo w in g e x e rc ise #

They

found t h a t h e a r t r a t e f e l l v e ry l i t t l e d u rin g t h e f i r s t t e n seconds a f t e r w ork, and f o r th e n e x t t e n seconds only about 6 p er c e n t.

2?hey re p o rte d

th e sta n d a rd d e v ia tio n o f v a r i a t i o n i n h e a r t r a t e d u rin g e x e rc is e a s 2.6

28

p e r c e n t, w h ile th e sta n d a rd d e v ia tio n o f change i n h e a r t r a t e i n th e f i r s t te n seconds a f t e r e x e rc is e was ah o u t 2 ,8 p e r cent*

They con­

clu d ed t h a t p u ls e r a t e d u rin g e x e rc is e may he p re d ic te d from t h a t r e ­ corded im m ediately a f t e r e x e r c is e w ith a n e r r o r whoso sta n d a rd d e v ia tio n i s l e s s th a n 3 p e r c en t* Boas and Goldschm idt (1932) found i n t h e i r work w ith tw e n ty seven young hoys t h a t w ith l i g h t e x e rc is e th e p u lse r a t e re tu rn e d to th e r e s t in g v a lu e s i n two m inutes o r le s s* p u ls e r a t e m ight rem ain h ig h f o r many hours*

A f te r heavy w ork, th e T heir stu d y in d ic a te d a

r a p id drop i n r a t e d u rin g t h e f i r s t two m inutes a f t e r e x e r c is e , th e n a v e ry slow drop o f about 10 h e a ts i n t h e n e x t h a lf h o u r, and 7 b e a ts i n th e succeeding h a lf hour*

O ther in v e s tig a to r s have found t h a t a f t e r

th e c e s s a tio n o f w ork th e p u lse r a t e f a l l s q u ic k ly a t f i r s t , th e n more slo w ly ; and a f t e r m oderate w ork, th e r e s tin g le v e l i s reach ed i n two to e ig h t m in u te s, h u t a f t e r h e a v ie r w ork, a lo n g er tim e i s re q u ire d *

Under

th e s e c irc u m sta n c e s, th e f a l l i n g p u lse curve shows b ig g e r or sm a lle r waves*

A com parison betw een th e f a l l i n p u ls e r a t e and th e oxygen i n ­

ta k e a f t e r th e c e s s a tio n o f work showed t h a t t h e p u ls e r a t e dim in ish ed more slow ly th a n th e oxygen in ta k e , e s p e c ia lly i n t h e e a r ly phase, (ly th g o e and P e r e i r a , 1925; Kagan and K aplan, 1930). A f u r t h e r stu d y o f p o s t- e x e r c is e p u lse r a t e (Morehouse and T u t t l e , 1942) showed t h a t environm ental s tim u li a f f e c t h e a r t r a t e and may overshadow th e a c t u a l r a t e u n le s s t h e e x e rc is e is stre n u o u s enough*

29

T h eir r e s u l t s a ls o in d ic a te d t h a t p o s t- e x e r c is e in c re a s e i n p u lse r a t e above r e s tin g le v e l i s d i r e c t l y r e l a t e d to i n t e n s i t y of e x e r c is e .

An

im p o rta n t f in d in g f u r th e r in d ic a te d t h a t th e re c o v e ry tim e i s prolonged i n r e l a t i o n to th e i n t e n s i t y o f th e e x e ro is e and i s n o t r e l a t e d t o th e r e s t i n g p u ls e r a te *

A secondary r i s e i n p u lse r a t e a f t e r e x e rc is e was

found to he a norm al h u t v a r ia b le phenomenon* The s tu d ie s review ed h e re r e v e a l t h a t th e c h a r a c te r o f th e h e a r t r a t e i n reo o v e ry i s d i r e c t l y in flu e n c e d by th e s e v e r ity o f th e e x e rc is e *

T his evidence p o in ts t o th e r e l i a b i l i t y and v a l i d i t y o f us­

in g th e imm ediate p o s t- e x e r c is e h e a r t r a t e a s a m easure o f i n t e n s i t y o f e x e r tio n , and i t s r a t e o f d e c e le r a tio n a s one p o s s ib le m easure o f re c o v e ry . (B) so u rce o f th e body*s heat*

Body te m p e ra tu re .

The m uscular t i s s u e s a r e th e m

D uring stre n u o u s m uscular e x e r c is e , t h e r e

i s a tem porary r i s e i n body tem p eratu re from 1° t o 4° F . ; a tem pera­ t u r e o f over 104° F* d u rin g e x e rc is e has b e e n re p o rte d ( H i l l , 1924)* This r i s e i n body te m p era tu re i s a p p a re n tly due n o t to any f a i l u r e o f th e h e a t d i s s i p a ti n g m echanism s, b u t to th e th e rm o s ta tic c o n tr o l b e in g s e t a t a h ig h e r l e v e l , f o r t h e te m p e ra tu re r i s e i s t h e same w hether th e e x e rc is e i s perform ed a t an a i r tem p era tu re o f 3° o r 23° C* (B e st and T a y lo r, 1950). D i l l and Edwards (1931) found t h a t th e r a t e o f in c re a s e i n body te m p e ra tu re a s work i s c a r r i e d on was n e a r ly c o n s ta n t f o r th e f i r s t few m inutes*

Then a new c o n s ta n t te m p e ra tu re was reach ed i f c o n d itio n s

30

f o r h e a t d i s s i p a ti o n were f a v o ra b le ; o th erw ise body tem p era tu re ro s e u n t i l e x h a u stio n in te rv e n e d . Some o f th e c o m p le x itie s in v o lv ed i n th e measurement o f body tem p era tu re were c it e d by Mead and Bonmarito (1 9 4 9 ), who s tu d ie d th e r e l i a b i l i t y o f r e o t a l te m p e ra tu re s .

They p o in te d ou t th e n e c e s s ity

f o r re c o g n iz in g th e com plexity o f th e p a tte r n s o f te m p era tu re w ith in th e i n t e r n a l mass o f th e body*

The te m p era tu re o f any re g io n i n th e

i n t e r n a l mass o f th e body depends on th e m e tab o lic a c t i v i t y o f th e r e ­ g io n , th e te m p era tu re and amount o f blood flo w in g th ro u g h th e re g io n and th e g ra d ie n ts o f te m p e ra tu re to su rro u n d in g reg io n s*

These f a c to r s

have been shown t o v a ry betw een re g io n s and w ith in th e same re g io n (Hepburn, 1932}•

F u rth e r , th e in v e s tig a to r s s ta te d t h a t th e d e v ia tio n

o f s in g le re g io n a l te m p e ra tu re from o th e r body te m p e ra tu re s or from th e a v erag e body te m p e ra tu re could b e e j e c t e d to v a ry w ith d i f f e r i n g le v e ls o f a c t i v i t y and am bient c o n d itio n s*

Of g r e a te r p r a c t i c a l im­

p o rta n c e th a n th e d e v ia tio n s o f d i f f e r e n t re g io n a l te m p e ra tu re s i s th e problem o f a c c u ra te ly p o s itio n in g any te m p e ra tu re re c o rd in g d e v ic e so as t o o b ta in r e l i a b l y th e te m p e ra tu re o f a s in g le reg io n *

I f th is is

n o t acco m p lish ed , te m p e ra tu re d if f e r e n c e s rec o rd ed may r e p r e s e n t tem­ p e ra tu r e g ra d ie n ts i n t h e body r a t h e r th a n te m p e ra tu re changes o f a p a r t i c u l a r re g io n . E xperim ents have been conducted t o d eterm ine t h e in flu e n c e o f body te m p e ra tu re upon h e a r t r a t e (B enson, 1934)*

R e s u lts o f th e s e

s tu d ie s showed t h a t h e a r t r a t e v a rie d d i r e c t l y w ith te m p e ra tu re o f th e

31

skin*

Body te m p era tu re , a s such, produoes an in c r e a s e i n h e a r t r a t e

m ainly i n so T ar a s c i r c u la t in g blo o d h e a ts up n erv e endings i n t h e sk in *

The in c re a s e i n body te m p e ra tu re r e f e r r e d to i n t h i s stu d y was

e f f e c te d by h o t b a th s and r a d i a n t heat*

The m ost in sta n ta n e o u s r e ­

sponse o f th e h e a r t t o changes i n b a th te m p e ra tu re s in d ic a te d t h a t i t i s a r e f l e x a c t io n , p ro b ab ly i n i t i a t e d th ro u g h s tim u la tio n o f nerve endings i n th e skin*

THE USE OF ERGOGRAPHS FOR STUDIES OF FATIGUE AND RECOVERY , The s c i e n t i f i c l i t e r a t u r e re v e a ls t h a t th e e r g o graph has b een employed alm ost e x c lu s iv e ly f o r th e purpose o f m easuring work o u tp u t to th e p o in t o f exhaustion*

F in g e r and hand ergom eters have been m ost

g e n e r a lly used i n th e stu d y o f sm all m uscle groups (M aggoria, 1890j Mosso, M anzer, W e ile r, Broca and R ic h e t, 1927)*

S ta n d a rd iz e d work o f

la rg e m uscle groups has b een s tu d ie d w ith th e u se o f th e b ic y c le e rg o m eter (W a llric h , 1920} T u t t l e , 1931; H e lle b ra n d t and K elso , 1934; F o ltz , Ivy and B arborha, 1942; F o l t z , E l l i o t and Jung, 1944), rowing machine (Amori, 1935), and w eighted p u lle y s (Manzer, 1927; Benson, 1934).

An

th e s e s tu d ie s were concerned w ith th e maximum o u tp u t o f energy and were approached from th e view p o in t o f m easuring p h y s io lo g ic a l changes t h a t o ccur i n th e human organism under such c o n d itio n s*

This i s n o t

t o say t h a t th e in v e s tig a to r s w ere unm indful o f such f a c t o r s as m o ti­ v a tio n a l and p sy c h o lo g ic a l problem s, b u t t h a t th e p rim ary purpose o f

52

t h e i r in v e s tig a tio n s was th e maximal o u tp u t w ith r e l a t i o n t o p h y s ic a l f a t i g u e and f itn e s s * The o n ly work s t r e s s mechanism re p o rte d i n th e l i t e r a t u r e which came c lo s e t o th e problem o f concern i n t h i s paper was t h e in g en io u s in stru m e n t p a n e l d esigned and c o n s tru c te d by B a r t l e t t and h is co­ w orkers to sim u la te t h a t found i n modern a i r c r a f t *

Working upon th e

assum ption t h a t f a tig u e does n o t n e c e s s a r ily c o n s is t o f dim inished e f ­ f ic ie n c y o f s p e c if ic perform ance due t o th e r e p e t i t i o n o f perform ance, th e y s e t o u t to stu d y th e c h a ra c te r o f f a tig u e r e s u l t i n g from h ig h ly s k i l l e d w ork.

S ig n a ls on th e p a n e l w ere d iv id e d i n to th r e e m ain g ro u p s.

The m iddle group o f s ig n a ls was im p o rtan t th ro u g h o u t th e experim ent* To one s id e was a n o th e r group which became im p o rtan t on ly a t c e r t a i n s t a g e s , and on t h e o th e r s id e w ere s ig n a ls im p o rtan t o n ly i n t e r m i t t e n t ­ l y b u t c a llin g f o r prompt, a tte n tio n *

Above and below were s tim u li

w hich could b e b ro u g h t i n a t th e experim ent or* s w i l l , each c a l li n g f o r a s p e c if ic response*

To a l l th e s e s ig n a ls t h e o p e ra to r responded by

c o -o rd in a te d movements o f hand, f e e t , eyes and u n derstanding* stim u lu s had a d e te rm in a te r e l a t i o n t o ev ery o ther* m ained s t a ti o n a r y a l l th e tim e*

Each

The machine r e ­

There was l i t t l e or n o th in g s h e e rly

r e p e t i t i v e i n th e s tim u li or i n th e b e h a v io r o f th e su b je c t*

Ho r e ­

sponse demanded s tro n g p h y s ic a l e ff o r t* The norm al co u rse o f th e experim ent showed a r e g u la r and p ro ­ g r e s s iv e ten d e n cy on th e p a r t o f th e s u b je c t to lower h i s s ta n d a rd o f perform ance*

W ith in t h e lim i ts o f f a tig u e s e t by t h e e x p erim e n t, he

33?

could c a r r y on th e l o c a l a c tio n s o f c o n tro l as w e ll as o r b e t t e r th a n e v e r , b u t he could n o t m a in ta in th e o rg an ized c o o rd in a te d and tim e d resp o n se s f o r more th a n a s h o r t p e r io d .

B a r t l e t t concluded t h a t i n

o rd e r t o s tu d y f a tig u e o f th e c e n t r a l nervous sy stem , one can n o t con­ f i n e th e d e te rm in a tio n s t o th e e f f i c ie n c y o f th e lo c a l r e a c t i o n mecha­ n ism s.

I n s te a d , th e th r e s h o ld o f ra n g e , a com bination o f th e sen se

and c e n t r a l c o n tr o l should be o b serv ed .

34

CHAPTER I I I METHODS AND PROCEDURES In o rd e r t o d i f f e r e n t i a t e betw een v a rio u s pro ced u res w ith r e ­ fe re n c e to t h e i r e f f e c tiv e n e s s i n f a c i l i t a t i n g re c o v e ry from s t r e s s r e s u l ti n g from a sim u la te d f l i g h t t a s k , th r e e problem s w ere under­ taken*

( l ) d e sig n in g and c o n s tru c tin g an a p p a ra tu s f o r t h e p e rf o r ­

mance o f a t a s k r e q u ir in g some o f th e components p r e s e n t i n th e o p e ra tio n o f a i r c r a f t , such a s c o o rd in a tio n , v is u a l re s p o n s e , d e c is io n and submaximal m uscular e f f o r t ; (2 ) determ in in g a n end p o in t f o r th e ta s k o th e r th a n p h y s ic a l e x h a u s tio n ; and (3) determ in in g th e r e l a t i v e v a lu e s o f s e v e ra l p ro ced u res w hich m ight be used by m i l i t a r y f l i g h t p e rso n n el t o f a c i l i t a t e r e c u p e r a tio n i n th e b r i e f p e rio d betw een suc­ c e s s iv e f l ig h t s * The p u r s u i t - m e t e r e r g o g r a p h *

To in d u c e a t y p e o f s t r e s s sim u­

l a t i n g th e t a s k o f p i l o t i n g a i r c r a f t , a n e rg o g ra p h w h ic h WDuld demand b o t h p h y s i c a l a n d m e n ta l e x e r t i o n o n t h e p a r t o f t h e s u b j e c t w as d e­ s ig n e d a n d c o n s tr u c te d *

T h is m echanism w as a c o m b in a tio n p u r s u i t -

m e te r a n d e r g o g r a p h a n d ^ c o n s i s te d o f a n a i r c r a f t s e a t w i t h b o x - l i k e arm s f a c i n g a l i g h t p a n e l w i t h f o u r l i g h t s o c k e ts so a r r a n g e d t h a t t h e y c o u ld b e f l a s h e d on i n a n y d e s i r e d o rd e r*

I n s t a l l e d i n e a c h arm

o f t h e c h a i r w as a l e v e r w h ic h w as c o n n e c te d t o a w e ig h t c a r r ia g e ; b y a l / 8 in c h a i r c r a f t c a b le *

The c a b le s r a n o v e r p u l l e y s an d w e re b o l t e d

t o t h e l e v e r b l o c k s , w h ic h s l i d a lo n g a t r a c k on f o u r r o l l e r s *

As t h e

35

le v e r s were p u lle d o r pushed, th e c a r r ia g e s s l i d up and down on two guide r o d s .

Five pound d is c s o r w eights w ere s lip p e d o v er a th re a d e d

rod i n t h e c e n te r o f th e c a r r ia g e and w ere h e ld i n p la c e by a w ing / .

b o lt.

Ifiihen e i t h e r o f th e , le v e rs was p u lle d o r pushed, th e c a r r ia g e

and th e w eights^ w ere r a i s e d ; and as th e c a r r ia g e rea ch e d i t s maximum l i f t , i t h i t a sm all m icro -sw ito h which was b o lte d to th e s id e p a n e l o f th e box*

When c o n ta c t was made, th e sw itc h opened th e c i r c u i t and

th e co rresponding l i g h t on th e p a n e l was p u t out* The arms o f th e c h a ir could b e moved forw ard or backward i n (

a d ju s tin g t o t h e arm le n g th o f each s u b j e c t .

An ir o n f o o t b a r a t

th e b a se o f th e o h a ir was a d ju s ta b le a c c o rd in g to th e le g le n g th o f each s u b je c t. The l i g h t p a n e l was su p p o rte d by fo u r m etal u p rig h ts fa s te n e d to t h e b ase o f th e fram e a t a d is ta n c e o f 50 in c h e s from t h e su b je c t* The l i g h t p a n e l had a l i g h t i n each c o rn e r and a f i x a t i o n jew el i n th e c e n t e r .

The l i g h t s f la s h e d on a t th r e e - f o u r th s second i n te r v a l s

and rem ained b u rn in g u n t i l t h e sub j e c t p u t them o u t by pushing o r p u l­ lin g th e a p p ro p ria te le v e r to r a i s e th e w eig h ted c a rria g e *

Behind

th e l i g h t p a n e l was a c i r c u i t box c o n ta in in g a c o n ta c t d i s c , re la y s and a 4-RFM m o to r, w hich tu rn e d a b ru s h over th e c o n ta c t p o in ts * c u r c u it c o n ta in e d f i v e d i f f e r e n t l i g h t p a t t e r n s .

The

These l i g h t p a tte r n s

o r sequences were changed a t r e g u la r i n te r v a l s t o p a r t i a l l y e lim in a te memory resp o n se by th e s u b j e c t .

36

The re c o rd

wrs

made on a kymograph c o n s is tin g o f a c y l i n d r i c a l

aluminum drum 3 in ch es i n d iam ete r d riv e n by a 1-RFM motor*

F aper was

drawn a c ro s s th e upper s u rfa c e b y th e re v o lv in g drum moving a g a in s t