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LA THESE A ETE MICROFILMEE TELLE QUE NOUS L'AVONS RECUE

THE EFFECTS UP FORCE, FATIGZfE, ALCOHOL,

ASPIRIN AND CAFFEINE ON TRE

Sunday Theoph i lus Eke-Okoro

B-Sc.. (Physiotherapy), University of Ibadan, N i g e r i a , 1975 -

- - - - - -

4- A THESIS SWMITTED IN PARTIAL FULFILLMENT OF

T m -REQUIREMENTS FOR THE DEGREE OF

.MASTER OF SCIENCE (KINESIOLOGY)

i n the Department

Kines io logy

Sunaay Theoph i lus Eke-Okoro 1979

Sf YON FRASER UNIVERSITY

J u n e 1979 /'

A l l r i g h t s r e s e r v e d . T h i s thesis may n o t b e - - - - - - - - - - - -- - -

-

- reFrmZucedl%wKoIe I n p=tT3y pho tocopy o r o t h e r mans, w i t h o u t peimission o f t h e aukhor.

PARTIAL COPYRIGHT LICENSE

I hereby grant to Sinon Fraser University the right to lend

my t h r i s or diesertation (the t i t l e of which i s rhom below) to users

of the Simon Ftastr Univers i ty Library, and to make partial or s ingle

e e p i e a only for- such users or in response t o a request f r m the library

-- - -- --- - - F a r ~ r d t i c a r T o n a 3 f n s r rtiitTi%t~%Tt s 'awn

behalf or for one.of its users. I fur ther agree that peredssiar for

w f t i p l e copying of t h i s rhesfs for scho>rly purposes lsay be granted -- -- -- - -- - pp - - - - - --- - - --

by me or the Dean of Graduate S t u d i e s . I t is understood that copylng

or publication of t h i s thesie for financial gain shall not be allowed

without my written permtssion,

Title of Thee is /D-

Author: - ( 8 igna tu re )

3 3 C

- (date)

Y a w : Sunday Theuphilus Eke-Okoro

Degree: Master of Science (~inesiology) *

Tit le of thesis: The effects o f force, fatigue, alcohol,

aspirin and caffeine on the Hoffmam

Examining Gmni t tee : - -

Qlainnan: f.1 .fi. Savage

d

T.K. Calvert Senior Supervisor

--

C.M. Davls Psychology Depar-tment

P.N. Bawa Kinesiology Department

ABSTRACT

The Hof fmann r e f l e x repyesents a ' r e l a t i v e l y unexplored ? -

phenomenon i n neurology and neurophysiology. I ts production -- -- - A- - - - - - - - - - - -

by e l e c t r i c a l s t imulus and i t s prominent responses make it

n o t only e a s i l y e l ' i c i t a b l e but a l s o r ead i ly q u a n t i f i a b l e . The

i t s presence i n the quadriceps femoris and h&an masseter has

been confirmed more recent ly . The purpose of t h i s study i s t o

use t h e H-reflex t o observe the e f f e c t s on the nervous system

of agents which have a widespread e f f e c t (a lcohol , a s p i r i n , and

ca f fe ine ) and agents which have a l o c a l e f f e c t ( f o r c e and

f a t i g u e ) , t o determine how sensLtive t e r e f l e x 'h for use as l"L a model of t h e nervous system and t o examine t h e p o s s i b i l i t y

of q u a n t i f i c a t i o n kn ref fex .testing.

Five paid undergraduate s tudents of d i f f e r e n t d i s c i p l i n e s

were used as sqbjects. The s u b j e c t ldy prone on = t a b l e with

pi l low supports for the head and ankle. A ground e l e c t r o d e was

s t rapped on t h e c a l f and su r face e l ec t rodes were placed j u s t ' - - - - - - - - -- - - - -- - -- - -- -- - - - -- - -- - - - - - --

below the c a l f . The s t imula t ing e lec t rode was a small cathode

placed i n the popl i teaf fossa while the i n d i f f e r e n t e l e c t r o d e

was l a r g e and placed j u s t below the p a t e l l a . Control recordings

were made j u s t be fo re t h e test condit ions were appl ied , c a r e -

iii

- - - -- -- ---

being t aken to ensure that s u b j e c t s d i d n o t al ter their

p o s i t i o n .

From the experiments i t was observed t h a t force, alcohol,

a s p i r i n , c a f f e i n e a ~ d f a t i g u e had s i g n i f i c a n t e f f e c t s on t h e

I t is suggested t h a t the f a c i l i t a t o r ~ e f f e c t s of alcohol

=d - d f e i ~ can be a -re QZ +he excitabilky oif- #e

nervous system. I t is inplied that q u a n t i t i e s of alcohol and *

c a f f e i n e great'eer than those used i n t h i s s tudy may n o t have

f a c i f i t a t o r y e f f e c t s and may have o t h e r non-benef ic ia l e f f e c t s

on the body. The e f f e c t of c o f f e e which was due t o i t s

caffeine c o n t e n t tf00-150 mg) was marked p o t e n t i a t i o n of the - - -

reflex and the direct muscle {MI response. This sugges t s an inc reased a r o u s a l of t h e nervous system.

The depres san t e f f e c t of a s p i r i n on the r e f l e x i n d i c a t e d

a depress ion of t h e nervous system, I t is known t h a t a s p i r i n

kills pain by depress ing pain r e c e p t o r s and suppress ing t h e

release o i b radyk in in - l i ke po lypept ides which produce pain .

projected t o be due t o inc reased feedback t o the h ighe r c e n t e r s

which f a c i l i t a t e the spinal c e n t e r s t o compensate f o r loss of

i v

force. Other observations in the fat5gue study w e r e the

gradual rise in i n t eg r a t ed EEfG (IEMG) and a marked depression

of the *response. fatigue produced by the method used i n this

ischemia than on neuromuscular j u n c t h f

-- - - - - --A

The reflex is projected as a d iagnos t i c tool for a number

of patholog ica l conditions and as a s e n s i t i v e measure of the - - - - -- - -- - - -- -- --

effects of drugs on the nervous system.

I w i s h t o express my s i n c e r e g r a t i t u d e t o D r . T. W.

Ca lver t , my Senior Supervisor , f o r h i s advice and support - -- - - -- -- - - - - - - - - - -

during this study. M y thanks -a lso go t o the o the r members of

t h e Thesis Committee ,for t h e i r guidance and a b i l i t y t o meet

even w h e n i t w a s impramp%& and ta khe A u d i o Y ~ ~ Depar-e

for making it poss ib le f o r m e t o produce acceptable f igures .

I would a l s o l i k e t o thank my.senior bor the r , Mr. Herbert

Eke-Okoro, f o r being a t r u e guardian.

TABLE OF CONTENTS f

A P P R O V A L . . . . . . . . . . . . . . . . . . . . . . . . . i i *

ABSTRACT. . . . . . . . . . . . . . . . . . . . . . . . . .iii ACKNCMLEDGEMENTS. . . . . . . . . . . . . . . . . . . . . . ,i

* . . . . . . . . . . . . . . . . . . . . . . LIST OF TABLES. x 6

L I S T O F F I G U R E S . , . . . . . . . . . . . . . . . . . . . . x i - ---- ~ LL-LAL-L---- ~~ --.. - ~ - -L- ~ ~ A

I .. INTR~DUCTION. . . . . . . : . . . . ' . . . . : . . 1

C h a r a c t e r i s t i c s o f the R e f l e x . . . . . . . . . - 4

r l i n i c a l a l l p r t a n ~ . ~ ~ , -, , , , * * * , * * - - * , -,- -4- - - - - -- 11. . R E V I E W O F TEE LITERATURE. . . . . . . . . . . . . 1 3

P h y s i o l o g i c a l Mechanisms Influencing the

. . . . . . H - R e f l e x , , . . . . . . . . . . . . . 1 4

V i s u a l Influences . . . . . . . . . . . . . . . 1 7

H e a d P o s i t i o n s . . . . . . . . . , . . . . . . . 1 7

Respiratory E T f e c t s T . . . . . . . . . . . . . . 1 8

. S l e e p . . . . . . . . . . . . . . . . . . . . . 1 8

C l i n i c a l A p p l i c a t i o n s . . . . . . . . . . . . . 1 9

P a r k i n s o n s ' s D i s e a s e . . . . . . . . . . . . . . 1 9 t

: Detection and A s s e s s m e n t of C e n t r a l , I

. . . . . . . . . Nervous Sys tern (CNS) L e s i o n s . 20

Determination of Motoneurone ~ x c i t a b i l i t ~ 22 1 . . . . i f !

Widely Accepted D i a g n o s t i c Areas . . . 22 . .

~- -- - - - -- - ~- -- -

- s A g e n t s u n d e r Study. 23 * . . . . . . . . . . . . . . .

vii '

- - - - - - - - -- -

1

/

Ill. MATERIALS AND HETRODS -. . . . . . . . . . . . . 25 1 - d 3

Experimental Object ives and Hypotheses . . , . . 25 Experimental Procedure . . . . . . . -, . . . . .. 28

F o r c e , . . . . . . . . . . . . . . . . . . . , 29

Alcohol. . . , , . . . . . . . . . . . . . . . 30 "

p i n ,,,. - - . . ., 2 4

C a f f e i n e . :. . . . . . . . . . . . . . . . . 31 4

Localized Fatigue. . . . . . . . . . . . . . . 31 -

---- - m. RESULTS. . . . . , .. . . . . . . . . . . . . . . 39 Data Analysis. . . . . . . . . . . . . . . . . . 4 5

Graphical Method . . . . . . . . . . . . . . . 4 5 ,'

Percentage Method. . . . . . . . . . . . . . . 45

Hmax/M Ratio . . , . . . . . . . . . . . . . . 46 - -

Histograms. . . . . . . . . . . . . . . . . . . 46

Measurements, . . . . . . . . . . . . .. . . . . . 47

N o r m a l . . . . . . . .. . . . . . . . . . . . . 50 Force. . . , . . . . . . . . . . . , , . . . . 50

A l c o h o l . , . . , . . . . . . . . . . . . . . 51 Aspirin. . . . . . . . . . . . . . . . . . . : 57

The Effec t s of Agents w i t h Widespread

Influence on

General. . Alcohol*

. Aspirin, ,

Caffeine .

. . f

the Nervous System. . 73

. . . . . . . . . . . . . . . . . . . . General. 76

. . . . . . . . . . . . . . . . . . . Force. ; 76 -

- - -- ppp- - - - - --- - - - -

. . . . . . . . . . . . . . . . . . . Fatigue. 77

. . . . . . . . . . ,Limitations and Future Work. 78 . I . . . . . . . . . . . . . . . . . . I . CONCLUSIUNS. 3 00

J - . . . . . . . . . . . . . . . . . . . . . . . . . APPENDIX A 81 . APPENDIX B . . . . . . . . . . . . . . . . . . . . 85 'r

Peak H - A r e p l i t d ~ s , ,- ,-, , -, ,--, ,-, , , + ,---, 83

Second to the Peak H-Amplitude . . . . . . ' . . . . . . . 84 . . . . . . . . . . Third to the Peak H-Amplitude. 84

. . . . . . . . . . . . . . Mean tias as (X,Y, 2 ) 85

. . . . . . . . . . . . . . . . . . . . . . . APPENDIX C 86

. . . . . . . . . . . . . . . . Standard Deviation 86

Deviations (6) . . . . . . . . . . . . . . . . . 86 . . . . . . . . . . . . . . . . . . . d squared. 87

Table Page

5 . Fatigue

zme.-hf kh3zSciaticme- - -- - 7 ,

The Lumbosacral Plexus 9

Method Used i n the ~ r o c G t i o n of the Hoffmann Reflex 11 - - ppp

Experimeritaf Design forp~laxed%asurements 33---

Experhental Design f o r t h e F o r q T e s t 35

Method Used to Study the. Effect of F a t j y u e on

the Hoffmann Reflex

H and M Recruitment Curves for a T y p i c a l Normal

-- - - -

Curves for T e s t and

with a Typical Subject t o Show Cont ro l Experiments

the Graphical Nethod of Data Analysis

p r i n t o u t Shwing the Effect on Stimulus I n t e n s i t y

1. Considered w i t h Control

-H and M Recruitmeat Curves with Alcohol compared

w i t h the C o n t r o l 55

12. I3 and M Recrui tment Curves f o r A s p i r i n 59

1 3 . H and N Recrui tment Curves f o r Ca f f e ine

Plotted with t h e Con t ro l

14. H o f fmaOl Ref lex Changes i*n Fat igue :

H and M Wave Response Curves, IEMG, and H/M R a t i o 63

1 5 . Hoffm d n Ref lex Changes i n Fa t i gue : _ -

The Experiment I l l u s t r a t e d i n F igure 1 4 was t

Repeated w i t h t h e Same Sub jec t .

i n Fa t igue

17. Bistograrn Showing t h e E f f e c t s of Tes ted Agents

0% t h e Hoffmann Reflex 69

xii

I. INTRODUCTION 1

A r e f l e x is a n a u t o m a t i c r e s p o n s e t o a s p e c i f i c s t i m u l u s .

and may b e med ia t ed by monosynap t i c , d i s y n a p t i c o r p o l y s y n a p t i c

pa thways , R e f l e x e s may be d e e p o r s u p e r f i c i a l . Deep r e f l e x e s a r e - - - -- - - - -- - - - -2

e l i c i t e d by s t r e t c h i n g m u s c l e s , ( e .g . t h e musc le s t r e t c h r e f l e x )

and s u p e r f i c i a l r e f l e x e s a r e produced b y - s t i m u l a t i n g t h e body

s u r f a c e , - ( e .g . t h e f l e x o r r e f l e x - c a u s e d by n o x i o u s s t i m u l i ) .

P a t h o l o g i c a l r e f l e x e s accompany d i s e a s e c o n d i t i o n s ; examples

i n c l u d e t h e B a b i n s k i r e s p o n s e and t h e g r a s p r e f l e x . Many

r e f l e x e s a r e e a s y t o tes t and are used t o m o n i t o r t h e

7 p h y s i o l o g i c a l s t a t e o f \ t h e neuromuscular sys tem. Al though t h e \ ---.

c h a r a c t e r i s t i c s o f a r e f l e x a r e n o t comple t e c o n f i r m a t i o n o f a

p a t h o l o g i c a l c o n d i t i o n t h e y may s u g g e s t it, w h i l e g i v i n g way to- --

more e l a b o r a t e methods o f e x a m i n a t i o n .

S t r e t c h r e f l e x e s are. i m p o r t a n t i n t h e c o n t r o l o f movement

and p o s t u r e . For t h e s e d e e p r e f l e x e s t h e r e c e p t o r s a r e musc le

s p i n d l e s and t h e g a i n s are c o n t r o l l e d by t h e h i g h e r c e n t e r s o f

t h e c e n t r a l n e r v o u s s y s t e m (Matthews, 1 9 6 8 ) . Thus i n upper motor

neu rone l e s i o n s ( p y r a m i d a l t r a c t l e s i o n s ) s u c h as- h e m i p l e g i a , t h e

s t r e t c h r e f l e x e s are f r e e d f r o m inhibition-EF-higkercenEers.- -

-m r e f - V e f o r e i n c r e a s ~ d 7 .L:- : m e s e aeep a m c ~ l l s r m a t - i s o f t e n c h a r a c t e r i z e d by c l o n u s . . U s u a l l y t h e t e s t i n g of

- - - - -- - * r e f l e x e s i n v o l v e s comparison wi th t h e o p p o s i t e body segments t o

de te rmine d e v i a t i o n from t h e normal, b u t t h e s e comparisons a r e

h a r d l y q u a n t i t a t i v e and canno t be f u l l y r e l i e d upon when

e s t i m a t h g t h e s e v e r i t y of a p a t h o l o g i c a l c o n d i t i o n . Thus t h e

need t o q u a n t i f y s p i n a l r e f l e x t e s t s canno t be overemphasized.

I t is f o r t h e purpose o f q u a n t i f i c a t i o n i n d i a g n o s t i c - -

r e f l e x o l o g y and f o r t h e e v a l u a t i o n of t r e a t m e n t - t h a t t h e

Hoffmann r e f l e x h a s become an impor tan t t o p i c o f r e c e n t

r e s e a r c h . Unques t ionably t h e r e f l e x h a s d e s i r a b l e

c h a r a c t e r i s t i c s f o r c l i n i c a l u s e , and t h i s r e s e a r c h is t h e r e f o r e - F;

d i r e c t e d towards d e t e r m i n i n g how t h e s e - c h a r a c t e r i s t i c s can be

b e n e f i c i a l l y u t i l i z e d .

The Hoffmann r e f l e x is a monosynaptic r e f l e x and it is t h e

e l e c t r i c a l e q u i v a l e n t o f t h e l e n d o n j e r k . I t was f i r s t ' desc r ibed

by Hoffmann, (1918) and was named t h e Hoffmann r e f l e x by

Magladery and McDougal, (1958) - Its s h o r t form d e s c r i p t i o n is

t h e H-reflex.

The s c i a t i c ne rve ( F i g . 1) from which t h e t i b i a 1 nerve

b ranches is t h e major n e r v e of t h e lumbosacra l p l e x u s (F ig . 2 ) - w i t h widespread r o o t s of o r i g i n i n t h e s p i n a l cord (L4,5,

4 - - - - - - -- -

S1,2,3), 1t is t h e l a r g e s t n e r v e i n the-human body and t h e

c e n t r a r m o t o r n e m n e poo l n n e r v a t e d muscles is extensi-.~ -Tii

view o f t h i s l a r g e motoneurone poo l , n e a r l y a n y t h i n g t h a t - (II

- -

a f f e c t s t h e lumbar and s a c r a l r e g i o n s w i l l a f f e c t some r o o t s of

t h e ne rve . The pr imary media to r of t h e g a s t r o c s o l e u s H-reflex i s

t h e t i b i a l nerve which is t h e l a r g e s t braneh of t h e s c i a t i c -

n e r v e , having c o n t r i b u t i o n from a l l i ts r o o t s , The H-reflex i s

o b t a i n a b l e i n t h e s o l e u s because t h e I a a f f e r e n t s are l a r g e r t h a n

t h e a l p h a motoneurone axons i n t h e t i b i a l nerve . The s e v e r a l f

r o o t s of t h e t i b i a l ne rve and i t s e x t e n s i v e c e n t r a l neurone pool

make t h e H-reflex a d i a g n o s t i c t o o l f o r morfitoring t h e n e u r a l

s t a t e of the l m b o s a c r a f r e g i o n and to some e x t e n t t h e s t a t e o f

t h e h i g h e r c e n t e r s .

. -

The method used t o produce t h e H-reflex is shown i n (Fig .

3 ) . E l e c t r i c a l pe rcu taneous s t i m u l a t i o n of t h e t i b i a & nerve

t a k e s p l a c e i n t h e p o p l i t e a l f o s s a . The s t i m u l u s (S) d e p o l a r i z e s

t h e a l p h a motoneurone axons r e s u l t i n g i n t h e development of

e l e c t r i c a l a c t i o n i n t h e e x t r a f u s a l f i b e r s . The M-wave

i n d i c a t i n g d i r e c t s t i m u l a t i o n o f t h e muscle t h e r e f o r e appears .

The s t i m u l u s a l s o c a u s e s a synchronous s t i m u l a t i o n o f t h e l a r g e

p r imary I a a f f e r e n t s g e n e r a t i n g an impulse t o t h e s p i n a l co rd

and t o h igher c e n t e r s . When t h i s impulse comple tes t h e

monosynaptic r e f l e x a r c , t h e H- r e f l e x is produced and is - - -- - -- - --

r e p r e s e n t e d by t h e H-wave recorded from t h e muscle. a

- - - - - - - - - - - - pp -

The a p p l i c a t i o n o f t h 9 e l e c t r i c a l s t i m u l u s a l s o produces a n

a n t i d r o m i c v o l l e y a long t h e l a r g e a l p h a motoneurone axons i n t h e

s p i n a l c o r d . When t h e s t i m u l u s is submaximal f o r t h e a l p h a

motoneurone axons , t h e a n t i d r o m i c v o l l e y w i l l g o t be s t r o n g

enough t o b lock t h e r e f l e x by c a l l i s i o n o r by a c t i v a t i n g s e v e r a l

Renshaw ce l l s . When t h e s t i m u l u s is maximal, t h e a n t i d r o m i c

v o l l e y ( F i g . 3) w i l l e l i m i n a t e t h e r e f l e x by t h e s e d u a l a c t i o n s .

C h a r a c t e r i s t i c s o f t h e R e f l e x

The H- re f l ex i s a monosynap t i c r e f l e x which is e l i c i t e d

w i t h modera te e l e c t r i c a l s t i m u l a t i o n b u t e l i m i n a t e d by maximal

s t i m u l a t i o n . The r e f l e x is due s o l e l y t o low t h r e s h o l d I a

a f f e r e n t s , m o s t l y f rom t h e t i b i a 1 b r a n c h o f t h e s c i a t i c n e r v e .

I t c a n be b locked by a n t i d r o m i c v o l l e y s and d e p r e s s e d by

p r e s y n a p t i c i n h i b i t i o n . The l a t e n c y rarlge i s appgox ima te ly 25 t o f a + , + +

30 m i l l i s e c o n d s and a m p l i t u d e r a n g e is approximate&y 0 . 4 4 t o 1.1

m i l l i v o l t s . The Hmax/Mmax r a t i o is i n t h e r a n g e 0 . 2 2 t o 0 . 6 9

(where tFmax and Mmax a r e maximum p o s s i b l e r e f l e x and musc le

r e s p o n s e s o b t a i n a b l e . d u r i n g expe r imen t ) . 4

C l i n i c a l Impor t ance

Owing t o t h e p r o j e c t e d impor t ance o f t h e H- re f l ex i n t h e

f i e l d o f n e u r o l o g y , it h a s become one o f t h e mos t s t u d i e d human

r e f l e x e s . Most w o r k e r s a r e i n agreement t h a t t h e r e f l e x f rom t h e - - - - - - -

s o l e u s and q u a d r i c e p s f e m o r i s c a n be o f use i n t h e f o l l y i n g - - - - - - - - - --

\

a r e a s : measurement and a s s e s s m e n t o f s p a s t i c i t y i n a v a r i e t y o f

m e d i c a l c o n d i t i o n s , d e t e r m i n a t i o n o f t h e e f f e c t i v e n e s s o f d r u g s ,

e .g. Levo-Dopa IL-Dopa) , Nembutal and Diazepam, e v a l u a t i o n o f

t h e p r e s e n c e of S 1 r a d i c u l o p a t h y , s t u d y i n g e a r l y e v e n t s i n

s p i n a l s h o c k , d e t e r m i n a t i o n o f m a t u r a t i o n i n t h e n e r v o u s sys t em

o f i n f a n t s , and t h e a s s e s s m e n t o f p rox ima l n e r v e c o n d u c t i o n i n

lumbar and s a c r a l d i s e a s e c o n d i t i o n s : Thus t h e r e is a g e n e r a l

need t o b e t t e r u n d e r s t a n d t h e meqhanism o f s p i n a l c o r d r e f l e x e s - - f

- -

and i n o r d e r t o d o t h i s , i t was d e c i d e d t o i n v e s t i g a t e t h e

e f f e c t s o f a v a r i e t y o f common a g e n t s which a r e known t o a f f e c t

The p r e s e n t r e s e a r c h w i l l i n v e s t i g a t e t h e e f f e c t s o f f o r c e ,

f a t i g u e , a l c o h o l , a s p i r i n , and e x . The

p o t e n t i a l b e n e f i t s o f t h i s \

u s e f u l t h e r e f l e x i s f o r u s e a s a model o f t h e n e r v o u s sys t em

and e x a m i n a t i o n o f t h e p o s s i b i l i t y o f q u a n t i f i c a t i o n i n t h e

&' t e s t i n g o f t h e r e f l e x . The w o ~ s h o u l d a l s o p r o v i d e a n / /

i n d i c a t i o n o f which n e r v e s i n t h e body have I a f i b e r s b i g g e r

t h a n t h e a l p h a motoneurone f i b e r s . I n t h e normal a d u l t s o n l y t h e

t i b i a 1 n e r v e , f e m o r a l n e r v e and n e r v e t o t h e m a s s e t e r musc le

have some f a f i b e r s b i g g e r t h a n a l l a l p h a motoneurones . I n

i n f a n t s many o t h e r n e r v e s c o u l d have l a r g e r I a f i b e r s , b u t a s

deve lopmen t takes p l a c e , t h e a l p h a motoneurones grow b i g g e r t h a n

c o n d i t i o n s , i f t h e 3 - r e f l e x c a n be e l i c i t ed i n c o n d i t i o n s where - - - - - - - - - - -

i t is n o t u s u a l l y p r e s e n t , t h e r e is an i n d i c a t i o n t h a t a l p h a

motoneurones have been a f f e c t e d .

I n Chapte r 2 , t h e h i s t o r y o f t h e H- re f l ex is rev i ewed and '

t h e l i t e r a t u r e o n i t s c l i n i c a l and r e s e a r c h a p p l i c a t i o n s i s

d i s c u s s e d . The l i t e r a t u r e on t h e e f f e c t s o f f o r c e , f a t i g u e ,

a l c o h o l , a s p i r i n , and c a f f e i n e on t h e n e r v o u s s y s t e m a r e

r ev i ewed . Chap te r 3 d e a l s w i t & e x p e r i r nen t a l . o b j e c t i v e s ,

hypotheses, equipment i t n d m e t h d s including e x p e r i t a e n t a l - --

p r o c e d u r e . I n C h a p t e r 4 , t h e methods o f d a t a a n a l y s i s a r e

d i s c u s s e d and t h e r e s u l t s o b t a i n e d from t h e d i f f e r e n t

e x p e r i m e n t s a r e r e p o r t e d , w h i l e Chap te r 5 c o n t a i n s d i s c u s s i o n

and c o n c l u s i o n s ,

Figure 1 The Course of the Sciatic Nerve

The Lumbosacral P l e x u s

Method Used i n t h e Produc t ion o f t h e

Hof fmann R e f l e x

- -

11. REVIEW OF TEE LITERATURE

me description of the Roffmann reflex by H o f f m a n n i n 1918

marked a new era i n reflexology. A d e t a i l e d study of the r e f l e x

was made by Magladery and McDougal (1950) . They repeated

Hof fmnnn's experiraent by s t imulat ing the t i b i a 1 nerve i n the

popliteal fossa and obtaining the r e f l e x from calf muscles.

H-ref l e x as a shoxt form description ( F i g . 3) .

H-Reflex in Other H u s c e f s

Although the reflex was originally obtained from the c a l f .

muscles - (gas trocso leus) , other workers have searched for the

r e f l e x i n other muscles of the body, I t has been obtained from

the quadriceps fernoris by s t imulat ing the femoral nerve i n the

femoral triangle just belw the inguinal ligament {Mungia, 1972;

Guiheneuc and Ginet, 1974). The reflex has been obtained from

hman arnsseter by God2tux and Desabedt (1975) who stimulated the

masseter branch of the raandibu1a.r nerve, and from hand muscles

by percutaneous stirsufatiCm of the u h a r nerve of newborns and

3 n e mamas anit Eiadz~rt ;-%XO F % = e w o r o n e , - - e - - --

I , f r r L% U L ~ ~ T -s lt . la . * 2

suppressed w i t h age jThnn;ln and L a b e r t , 1960) It has also

been obtained f rasa Irax2.s of spastic patients tTeasdall, et al.

1952) .

Phys io log ica l Mechanisms In f luenc ing t h e H-Reflex

Having i d e n t i f i e d t h e r e f l e x i n man it became neces sa ry t o

i d e n t i f y the f a c t o r s which c o n t r i b u t e t o the r e f l e x and h& it . .

can be b e n e f i c i a l t o c l i n i c a l neurology. The r e l a t i o n s h i p

between motoneurone pools i n t h e s p i n a l cord and t h e H-reflex - -

has been s t u d i e d . J e f f e r s o n and Benson (1953) determined t h a t

between 12.5 t o 2 6 . 5 p e r c e n t of the motoneurone pool i n t h e

s p i n a l cord f i r e i n t h e product ion o f t h e H-reflex. Angel and

Hoffmann ( 1 9 6 3 ) showed t h a t t h e f r a c t i o n of motoneurone pool

involved i s r ep re sen ted by t h e H/M f r a c t i o n (where H and M a r e

B- and H-wave anpfitudes) . T a b r i k o v a (1966) i n i t i a l l y

r epo r t ed t h a t i n m a n 100 pe rcen t of t h e motoneurone pool i s

involved. When Taborikova and Sax (1968) repea ted t h e e a r l i e r

i n v e s t i g a t i o n s they concluded that as smal l a s 24 pe rcen t ,

u s u a l l y 50 p e r c e n t and sometimes v i r t u a l l y 100 p e r c e n t of

motoneurone pool could be involved i n t h e e l i c i t a t i o n of t h e

reflex. The fraction of mtoneurone pool f i r i n g depends on t h e

background f a c i f i t a t i o n during t h e experiment and can t h e r e f o r e

aibiays f a l l within h e ranges p o s t u l a t e d by both g r o u p s o f

~~~~~~~~~m-inf+ence is that t he s t z e n g t h o f t h e r e f l e x

de-ends on t h e g e n e r a l a r o u s a l of the nervous system.

The con t ro l of t h e H-reflex from t h e h igher c e n t e r s has I

been t h e s u b j e c t of controversy: Accumulating evidence is i n

favour of a t l e a s t some supraspina l cont ro l . J endrass ik ' s

manoeuvre ( a f t e r Ernes t Jendrassik, a Physician i n Hungary,

1858-1921) is a technique by which a s u b j e c t hooks t h e f i n g e r s

of two hands together and f o r c i b l y p u l l s one a g a i n s t t h e o ther .

The manoeuvre was o r i g i n a l l y used f o r t e s t i n g of t h e knee jerk

r e f l e x b u t now it is being used i n t e s t i n g o t h e r r e f l e x e s a l so .

The e f f e c t of t h i s manoeuvre on t h e H-reflex is t h a t of

f a c i l i t a t i o n (Mark, 1963; F e r r a r i , e t a l . 1966; and Bussel, e t

a l . 1978) . The mechanism by which Jendrass ik ' s manoeuvre

f a c i l i t a t e s t h e H-reflex i s no t completely c l e a r . Burg, e t a l .

(1974) reported t h a t p o t e n t i a t i o n of the r e f l e x i s due t o

fusimotor d r ive . Spindle a c t i v a t i o n i s o f t en accompanied by

some cont rac t ion of t h e e x t r a f u s a l f i b e r s meaning i n d i r e c t alpha

motoneurone a c t i v a t i o n . Bussel, e t a l . (1978) emphasized t h a t

f a c i l i t a t i o n of the Hoffmann r e f l e x is no t s o l e l y due t o gamma

e motoneurone a c t i v a t i o n b u t t h a t d i r e c t alpha motoneurone

a c t i v a t i o n could be an important con t r ibu t ing f a c t o r . '

Though- p o t e n t i a t i o n of t h e H-ref l ex by Jendrass ik ' s

manoeuvre has t o a l a r g e e x t e n t been a t t r i b u t e d t o fusimotor - - - - -- - - - - - - --

a c t i v a t i o n , Procaine block of fusimotor f i b e r s i s unable t o end - - p~

- ~

p o t e n t i a t i o n (Taborikova, 1973). I t i S the re fo re pos tu la ted

t h a t t h e supraspina l inf luences a p a r t from a c t i n g on gamma

motoneurones a l s o a c t on alpha motoneurones increas ing t h e i r

e x c i t a b i l i t y (Taborikova, 1 9 73) . In acute s p i n a l shock,

a r e f l e x i a is due t o t h e cessa t ion of supraspina l inf luences .

I t has been suggested t h a t s t imula t ion of t h e a n t e r i o r I

cerebellum reduces t h e e x c i t a b i l i t y of motoneurones and could

depress o r even e l imina te t h e H-reflex through presynapt ic

i n h i b i t i o n (Morris and Penn, 1978) .

Taborikova (1973) has surmised t h a t t h e following t r a c t s

a r e t h e routes f o r supraspina l inf luences on t h e Hoffmann

re f l ex : Cor t icospina l t r a c t (CST) t o the motoneurones and

s p i n a l interneurones; t h e r e t i c u l o s p i n a l t r a c t (ReST) t o the

s p i n a l motor cen te r and t o t h e motoneurones. The

ves t ibu losp ina l t r a k/ (VST) appears t o inf luence t h e moto-

neurones e i t h e r v i a t h e interneurones o r d i r e c t l y . n

The inf luence of the v e s t i b u l a r system on propriocept ive

r e f l exes of human lower limbs has been inves t iga ted (Delwaide

and Delbecq, 1973). They reported po ten t i a t ion of tendon

r e f l e x e s bu t n o t t h e H-reflex. Probably t h i s would i n d i c a t e

a pa thologica l condi t ion-

Visual Inf luences

Evidence of v i s u a l inf luence on the r e f l e x i s a v a i l a b l e

i n the l i t e r a t u r e . Using b l indfolded and eyes-open s u b j e c t s ,

Shashami(l977) s tud ied v i s u a l inf luence on t h e Hoffmann

r e f l e x . In t h i s s tudy , - re f l ex amplitude w a s depressed w i t h - - A

bl indfolded and enhanced with eyes-open subjec ts .

Po ten t i a t ion i n eyes-open sub jec t s could be due t o increased

s t imula t ion of the eyes compared t o t h e decreased s t imula t ion

of b l indfolded sub jec t s . This implies t h a t t h e f i r i n g r a t e of

t h e c e n t r a l nervous system i n eyes-open s u b j e c t s is g r e a t e r

than f o r b l indfolded sub jec t s .

Bead Pos i t ions

The e f f e c t of t o n i c neck r e f l e x e s on t h e H-reflex was

s tud ied by Isaacs , e t a l . (1968) They repor ted i n c o n s i s t e n t

r e f l e x changes a s soc ia ted with pos i t ions of t h e head and i t s

movements. Hayes and Sul l ivan (l976) reported g r e a t e r

H-reflex amplitude when t h e r i g h t l e g w a s t e s t e d with s u b j e c t

looking t o the r i g h t than i n any o t h e r head pos i t ion ,

Respiratory Ef fec t s

Forced i n s p i r a t i o n causes f a c i l i t a t i o n of the Hoffmann

r e f l e x b u t nonnal r e s p i r a t i o n produces no v i s i b l e e f f e c t s

(Bishops, e t a l . 1970). F a c i l i t a t i o n of t h e r e f l e x i n forced

i n s p i r a t i o n i s l i k e l y due t o t h e s t rong muscular con t rac t ion

a s seen i n Jendrass ik ' s manoeuvre. Although t h e gamma

motoneurones a r e t h e primary r e c i p i e n t s of f a c i l i t a t i o n

(Bishops, e t al. 1970) t h e alpha motoneurones a l s o con t r ibu te

t o r e f l e x f a c i l i t a t i o n .

Sleep

Hodes and Dement (1964) inves t iga ted t h e r e f l e x i n man

during low vol tage electroencephalograph (EEG) s l e e p and

not iced t h a t the r e f l e x was depressed i n rapid eye movement

(REM) s l e e p and enhanced i n relaxed wakefulness. A s i m i l a r

r e s u l t was e a r l i e r reported i n i n f a n t s odes and Gribetz ,

1963) . The pathways involved i n t h e depression of t h e r e f l e x

i n (REM) s l e e p have been s tud ied (Shimizu, e t a l 1966) .

C l i n i c a l Appl ica t ions

Parkinson ' s Disease

Changes i n tKe H-reflex i n Parkinsonian syndrome p a t i e n t s

have been s t u d i e d . While doing electromyographic s t u d i e s of

monosynaptic r e f l e x e s i n t h e s e p a t i e n t s I o ~ u , e t a l . (1965)

n o t i c e d abnormal f a c i l i t a t i o n of t h e r e f l e x e s . Inc rease i n

a lpha motoneurone e x c i t a b i l i t y i n Parkinsonism,was r epo r t ed

by McLeod, (1972).

P a r k i n s o n ' s ' d i s e a s e i s g e n e r a l l y t r e a t e d wi th L-Dopa, and

t h e e f f e c t of t h i s drug on t h e H-reflex has been i n v e s t i g a t e d ' d

i n p a t i e n t s (McLeod and Vander Muelen, 1972; Herbinson, 1973).

The f a c t t h a t L-Dopa depresses t h e ampli tude of t h e H-reflex was

obta ined by bo th groups of workers. I n h i s own s tudy of t h e ,

e f f e c t of L-Dopa on the r e f l e x , Sax, e t a l . (1976) suggested

t h a t t h e rate of r e y v e r y of depressed r e f l e x curve could be 1

used t o determine e f f e c t of medication on r e f l e x a c t i v i t y .

..

-

Detection and Assessment of Central Nervous System (CNS) Lesions

Measurement of t h e Hoffmann r e f l e x appears t o be a

s e n s i t i v e method of de tec t ing and assess ing upper motoneurone

l e s i o n s (Upton, e t a L 19 72) . Increased motoneurone

e x c i t a b i l i t y and hyper re f l ex ia i n p a t i e n t s with upper

motoneurone l e s ions have been reported by Magladery, e t a 1

(1952). Diamantopoulos and Zaner (1967) observed an i n i t i a l

decrease i n s p i n a l motoneurone e x c i t a b i l i t y followed -by

increased motoneurone e x c i t a b i l i t y . Garcia-Mullin, and Mayer

(1972) s tud ied a l l grades of vascular hemiplegia and observed a

decrease i n motoneurone e x c i t a b i l i t y within t h e f i r s t two days

compared t o t h e unaffected limb. In some hemiplegics whose

cases had become purely chronic , an increase i n motoneurone

e x c i t a b i l i t y was obtained. The r e f l e x was a l s o obtained from

t h e a m muscles of t h e chronic hemiplegics.

With t he production of t h e H-wave, a temporary depression

of t h e a n t e r i o r horn c e l l e x c i t a b i l i t y occurs, causing an

i n t e r v a l of 100 t o 200 mil l iseconds t o e l apse before another

13-wave can be produced (Magladery, e t a1.1952) . Campbell,

and Green (1964) have shown t h a t the i n t e r v a l - between two

successive H-waves decreases - i n cases - - of upper - - motoneurone -

l e s ions . The reduction i n i n t e r v a l they claimed i s due t o

f a c i l i t a t o r y impulses a r r i v i n g a t the a n t e r i o r horn c e l l s .

I n c l i n i c a l absen&s ( s e i z u r e s ) , it has been shown t h a t

i n i t i a l f a c i l i t a t i o n i s almost always followed by i n h i b i t i o n

of t h e H-reflex (Rabending, 1967). The marked succeeding in-

h i b i t i o n may be an at tempt by the body t o end t h e s e i z u r e by

reducing t h e excess ive sudden discharge of t h e grey matter.

Graphospasm i s a d i sease charac ter ized by d i f f i c u l t y i n

wr i t ing . Kaneko, e t al. (1966) s tud ied t h e H-ref l e x i n

p a t i e n t s with t h i s condi t ion, They obtained c a l f H-ref lexes

from t h e sub jec t s while wr i t ing t h a t d i d n o t d i f f e r markedly

from r e s t i n g normal s u b j e c t s ; i n the p a t i e n t group t h e H-wave

amplitude obtained while w r i t i n g was twice, t h e value i n

r e s t i n g s t a t e . I n normal sub jec t s t h e r e a r e l i t t l e o r no

a l t e r a t i o n i n H-wave amplitudes during son ic , p h o t i c

s t ~ u l a t i o n , mental a r i thmet ic and hypervent i la t ion (Sobue,

c i t e d i n Kaneko, e t al . 1966).

4 The r e l a t i o n s h i p between ankle je rk and Hoffmann r e i l e x e s

i n muscle dystrophy has been s tud ied by Singh, e t al. (1971). , r

They s tud ied t h e following types: Duchenne, ~ d b ~ i r d l e and

Facioscapulohumeral. I n t h e Duchenne type they repor ted

H-reflex being absent i n 7 of 11 cases with bilateral. ~ ~ J L I x - - - -

*

i e r k s . This would mean t h a t only 4 had H-reflexes. I n t h r e e

cases with u n i l a t e r a l ankle jerk, t h e H-reflex w a s absent on both

s i d e s . It w a s absent i n two cases where ankle je rks w e r e absent.

In the Limbgirdle type, H-reflex of small amplitudes was

p resen t i n 2 of t h e 5 cases s tudied where ankle je rks were

present . In t h e remaining 3 cases t h e r e w e r e no H-reflexes.

In the Facioscapulohumeral type, of the two cases s tud ied t h e

H-reflex was absent i n one i n which ankle je rk w a s absent , I n

t h e o the r case t h e ankle jerk was normal and an H-reflex of

s m a l l s i z e was produced (it i s poss ib le t h a t t h e I a a f f e r e n t

had been a f f e c t e d by the d i s e a s e ) . They concluded t h e i r tests

with the observation t h a t t h e H-reflex i s a more s e n s i t i v e

index than the ankle je rk .

Determination of Motoneurone E x c i t a b i l i t y

S tudies have been done on haw t h e H-reflex could be used

t o determine t h e e x c i t a b i l i t y of motoneurones (Yap, 1967; Tobin,

1969) . Got t l i eb and Agarwal (1972) studying t h e r o l e of t h e

myotat ic r e f l e x i n voluntary con t ro l of movement (voluntary

i sometr ic p lan ta r f l ex ions and dors i f l ex ions of t h e f o o t a t t h e

a n k l e ) , suggested t h a t the peak-to-peak amplitude of t h e H-wave

is propor t ional t o t h e s e n s i t i v i t y of t h e s p i n a l r e f l e x arc .

They a l s o observed enhancement of r e f l exes during s p a s t i c i t y .

The eventual prominence of t h e H-reflex as a d iagnos t i c

t o o l is the r e s u l t of i t s ingenious study by s e v e r a l wqrkers

(Angel and Hoffmann, 1963; Weaver, e t al.1963; Diamantopoulos

and G a s s e l , 1965; Guiheneuc and Ginet, 1973, 1974; Braddom and

Johnson, 19 74 ; Notermans and ~ i n g e r h o e t s , 19 74 ; and Schuchmann , 1976, 1978) . The use of t h e H-reflex as a d iagnos t i c t o o l i n

r o o t compression of L5 and S1 has been suggested by Notermans

an&.uirlgerhaeh (1974) ; and Schuchmann (1976, 1978) . Thex have- - --

shown t h a t la tency w i l l increase i n r o o t compression. The use

of t h e r e f l e x as a d iagnos t i c t o o l i n S1 root compression was

emphasized by Braddom and Johnson (1974) who enumerated severa l

workers' suggestions f o r c l i n i c a l app l i ca t ions a s follows:

a n t e r i o r t i b i a 1 muscle H-reflexes a r e d iagnos t ic (except f o r

i n f a n t s ) of c e n t r a l nervous system les ions from t h e brainstem

ros t ra lwards , i n proximal neuropathy and S1 radiculopathy the

H-reflex may be absent o r show a delayed la tency when present ,

t h e presence of t h e H-reflex i n t h e arm of i n f a n t s a f t e r t h e

age of one is d iagnos t ic of c e n t r a l nervous system immaturity

dysfunction.

Agents Under Study

Apart from loca l i zed f a t i g u e and fo rce , none of t h e agents

t o be s tud ied has been s tud ied v i a the H-reflex. The e f f e c t s of - -- --- -- --- -

l o c a l i z e d f a t i g u e on the H-ref lex have been reported by Hayes

C1975F, GZDietZ (1978) . Both workers reported p o t e n t i a t i o n of

t h e r e f l e x i n f a t igue . Other r e l a t e d experiments on f a t i g u e

include, Romanul (1965) ; Stephens and Taylor (1972) ; and

Stephens, e t a L ( 1 9 7 3 ) who showed a depression of the EMG

amplitude i n f a t igue .

Got t l i eb and Agarwal (1972) demonstrated p o t e n t i a t i o n of ,

t he H-reflex with p lan ta r f l ex ion and depression wi th

dors i f lex ion . Dming p lan ta r f l ex ion , a s t h e force in the c a l f

muscles increased, t h e H-reflex increased r e f l e c t i n g increased

f a c i l i t a t i o n of t h e t r i c e p s motoneurone pool. During

dors i f leqdion; when t h e t ibia1i.s muscle is Contracting, t r i c e p s

alpha motoneurones rece ive rec ip roca l i n h i b i t i o n and hence t h e

H-reflex is depressed.

I11 : MATERIALS AND METHODS

1

Experimental Object ives and Hypotheses

One purpose of t h i s study is t o explore t h e e f f e c t s of

some agents which have a widespread inf luence on the nervous --

system (a lcohol , a s p i r i n , ca f fe ine ) on t h e H-reflex. A second

purpose was t o study the e f f e c t s of loca l i zed phenomena ( fo rce

and f a t i g u e ) . The i n t e n t was t o v e r i f y how s e n s i t i v e the

r e f l e x is f o r use a s a model of t h e nervous system, t o examine

the p o s s i b i l i t y of q u a n t i f i c a t i o n i n r e f l e x t e s t i n g and t o s e e

har it could be b e n e f i c i a l i n understanding s p i n a l mkor cantxol,

It was hypothesized t h a t a lcohol of t h e quan t i ty t o be used

in t h i s study would p t e n t i a t e the H-reflex. L m , e t a L (1962)

have shown t h a t l a w concentrat ions of alcohol f a c i l i t a t e , -C

human neuromuscular junct ions. Aspir in may depress t h e H-reflex

s i n c e i t i s able t o suppress pain and headache which are of

nervous o r i g i n , Caffeine would be expected t o p o t e n t i a t e t h e

the H-reflex (Gottlieb and Agarwal, 1 9 7 2 ) . In this study

sustained force wauld b& applied and as such a depression of the

El-reflex would be e x p e c m * d . Fatigue may potent ia te the r e f l e x , ,

as such an effect w a s reported by Hayes i n 1975.

%r

.Xethods and Equipmerit

-- -- f i v e noma1 mafe Waergra&ate students between the ages

4 a,

3 .

of 19 and 28 were chosen as subjects.\ ..They were selected on the %

b a s i s that their H-reflex was easily e l , i c i tab le from their calf - - - - - -

e

suscles and that they had accepted the condit ions of the

experiments by s icping the subject consent forms-see Appendix -

Af .

head

mey w e r e all ?aid f o r their s e r v i c e s , .

~ u b j e c t s l a y prone on a table with pi l l ow support for the

and a n k l e s . They w e r e c a m p l e t e l y relax& d w e r e not i

allowed to move f r o m the correct p o s i t i o n . The neck 'zfemained

s t r a i g h t such that the head was not turned to any s i d e during

the period of the expr iment . Tfie pillow support for the Can)cle

served a- dual purpose. F i r s t l y , it contributed with another

arrang-nt below it to maintain the ankle and knee at the

reqaired angles. Secondly, it improved the subject's relaxation ;

by releasing tension in the h a s t r i n g s . The angle between the

flexion (Fig, 4 ) .

The ground electrode (16x2 a) w a s placed on the middle of

the c a l f such that it fitted the circumference of the l e g , and

was connected to the BE preamplifier. The recording surface

e l e c t r o d e s w e r e p f a d 3 a. apart at the lower border o f the

ca l f along the midlinel These elecixodes were then connected

of a large anode (6x4 cm.) placed just below the pate l la and a

s m a l l cathode of diameter 3 . 2 cm. T h e cathode was placed on

was d i r e c t l y below it.

The stimulating current was drawn from an Ortec 4710 Dual

Channel Stimulator. The c u r r e n t passed through an SIU 4678

Grass i so la t ion unit t o which the electxodes were connected. - - - - - -

Xectangular wave pulses of 0 . 7 to 1.0 milliseccmds duration were

used i n a l l experiments, Stimulus was also fed to the TECA EMG

Unit to produce a stimulus channel on the output display for

comparison with the channels.

Connections from the s t imula tor and TECA EMG U n i t t o the

osc i l loscope i n f r o n t of the sub jec t made it poss ib le for the

output t o b e displayed. T h i s arrangement made it poss ib le fo r

the subjec t t o a t t e a p t t o a l t e r the r e f l ex and a l s o fo r the

experimenter t o determine when the r e f l ex response had been

obtained. For the purpose of this research, both the 8- and - L

H-waves were required.

Ln addition W tests in a relaxed s t a k e , the ~ e f l e x was

a l s o s tudied w i t h muscular e f f o r t . I n t h i s case the s u b j e c t ' s

t e s t foot was comfortably strapped onto a force tranducer t h a t

was connected t o an amplif ier which formed a channel of the TECA

EMG U n i t . The amount of force exerted by the foo t of the sub jec t

was displayed on the osci l loscope and voluntary fo rce regula t ion

was poss ib le a s the sub jec t could see the d i sp lay i n f r o n t of

him. The re f l ex was recorded w i t h d i f f e r e n t force values t o he lp

determine how d i f f e r e n t force l e v e l s a f fec ted the r e f l e x

response. a lues were measured w i t h the force transducer P6-.

which was c a l i b r a t e d w i t h a known force value before each

experiment ( f i g . 5 ) .

Zxper i s e n t a l Procedore

The followinggexXX=r iaentsf measurements were made: --

I. a . %- and H-waves in t he normal relaxed s u b j e c t s ( s t i m u l u s

only) . B- and M-wave changes with fo rce i n the normal

relaxed s u b j e c t s . H- and M-wave changes with alcohol i n t h e relaxed . sub jec t s .

H- and Mrwave changes with a s p i r i n i n the- relaxted- - --

sub jec t s .

H- and M-wave changes with ca f fe ine i n relaxed

sub jec t s .

H- and M-wave i n loca l i zed fa. t igue of t h e c a l f

muscles.

The experiments were done i n the same o rde r f o r a l l

sub jec t s . There was an i n t e r v a l of a t l e a s t one day between

one test and another. Subjec ts were advised before t h e day - -

of each test n o t t o take any of the agents as food before

r epor t ing f o r experiment. When sub jec t s repor ted f o r . t h e

experiment they w e r e again asked by the experimenter what they

had taken f o r a meal j u s t before repor t ing f o r t h e tests.

Force

This involved app l i ca t ion of sus ta ined and regula ted fo rce , - - - - - ---- - - - -

the force transducer having been previously c a l i b r a t e d wi th a - - -

known i o rce . The sub~ect e x e r t e a regula ted ro rce on the E O r C e

t r ansduce r and record ings of t h e r e f l e x were made a s soon a s -3 t h e r equ i r ed f o r c e va lue was seen on t h e o s c i l l o s c o p e .

Alcohol

A 6 oz, g l a s s of L a b a t t ' s Blue b e e r (5% a l coho l ) w a s g iven

t o each s u b j e c t and a f t e r wa i t i ng f o r one hour f o r t h e a l c o h o l

t o e n t e r t h e c i r c u l a t i o n , t h e r e f l e x was monitored (blood

a l coho l concent ra t ion reaches peak va lue one hour a f t e r i n t a k e ,

J (Wallgreen and Barry, 1970) . For average s u b j e c t t h i s

! would g i v e a blood a l coho l concent ra t ion of 0.012 p e r c e n t (6 oz.

of whiskey f o r average ' s ized man i s about 0.12%, Cohen, 1966) .

Aspi r in

A dose of two a s p i r i n t a b l e t s (10 g r . ) w'as given i n each

case . Asp i r in c o n t e n t of t h e blood reaches i t s peak between

1.5 t o 2 hours a f t e r it has been taken (Wilson, e t a l . 1975) . Thus H-responses w e r e recorded 1 .5 hours a f t e r a s p i r i n had been

taken.

C a f f e i n e

S u b j e c t s were g i v e n a t e a c u p f u l l o f Nescafe brand i n s t a n t

c o f f e e (1.3 g ) . I t was a normal l i g h t c o f f e e ( c a f f e i n e c o n t e n t

a b o u t 100-150 mg.). Recordings were made a f t e r one hour when

much of t h e c o f f e e was expec ted - - t o have been d i g e s t e d and pa-ssed _

i n t o t h e g e n e r a l c i r c u l a t i o n .

\ Loca l i zed Fa t igue

The s u b j e c t s tood on h i s t o e s on one l e g wi th t h e weight on

t h e f r o n t o f t h e f o o t (F ig . 6 ) ; t h e hands were used t o main ta in

ba lance . The p o s i t i o n o f t h e f o o t remained unchanged throughout

t h e p e r i o d of t h e exper iment . The r e f l e x was moni tored every

minute u n t i l t h e s u b j e c t c o u l d n o t c o n t i n u e ; each t i m e a

r e c o r d i n g was made t h e p o s i t i o n o f t h e h e e l above t h e wooden

p l a t f o r m was checked. T h i s was done by p l a c i n g a s m a l l c a r t o n

below t h e h e e l such t h a t t h e h e e l j u s t f e l t it d u r i n g t h e

r e c o r d i n g p e r i o d .

For a l l t h e a g e n t s t e s t e d , t h e s t i m u l a t i o n v o l 1 a g e s

depended on t h e a b i l i t y of t h e s u b j e c t t o endure

s t imul i r s pu l se mpmtuae r a n g a b e t w e e T 2 4 a i i ~ ~ m v ~ t ~ ;

- - - -

The EMG a m p l i f i e r s e n s i t i v i t y was between 100 and 500

m i c r o v o l t s per d i v i s i o n w i t h a sweep d u r a t i o n o f $00

m i l l i s e c o n d s pe r d i v i s i o n . The paper speed was u s u a l l y 50

c e n t i m e t e r s pe r second and t h e low and high c u t o f f f r e q u e n c i e s

of t h e EMG a m p l i f i e r s we- set a t 50 h z t o 5 Khz r e s p e c t i v e l y .

The f requency of s t i m u l a t i o n was one s t i m u l u s p e r f i v e seconds.

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IV. RESULTS 4 -

I n o r d e r t o o b t a i n u s e f u l i q f o r m a t i o n from t h e e x p e r i h e n t a l

d a t a , i t was n e c e s s a r y t o c o n t r o l , wherever p o s s i b l e , f o r . s y s t e m a t i c and random v a r i a t i o n s in t roduced by a number o f - .

- -

f a c t o r s . T h i s is b e s t unders tood wi th t h e a i d o f d iagrams

showing t y p i c a l d a t a c o l l e c t e d i n an exper iment ( F i g . 7 and 3).

These f i g u r e s a r e t y p i c a l of t h e v a r i a t i o n s o f H- and

M-wave ampl i tudes w i t h s t i m u l u s v o l t a g e f o r most e x p e r i m e n t a l

s i t u a t i o n s and d a t a were b o l l e c t e d . t o a l l o w s-uch c u r v e s t o be ..

drawn f o r a l l exper iments e x c e p t t h o s e i n v o l v i n g f a t i g u e . The

c u r v e s l a b e l l e d H(c) and H(c ) r e p r e s e n t d a t a c o l l e c t e d under a

norial o r c o n t r o l s i t u a t i o n and B ( s ) and Hfsj r e p r e s e n t d&- ' - - -

c o l l e c t e d under a n e x p e r i m e n t a l s i t u a t i o n (e.g. w i t \ a l c o h o l ) .

The f o l l o w i n g p o i n t s summarize t h e d i f f i c u l t i e s i n

a n a l y z i n g d a t a i n t h i s s t u d y .

1. For a g i v e n s u b j e c t i n a g i v e n exper iment , t h e response

c u r v e s w i l l v a r y w i t h t i m e . T h i s can be due t o changes a t

t h e sk,in e l e c t r o d e i n t e r f a c e f o r bo th s t i m u l a t i n g and

recofding erectyodes a n d t o c h a n g e s p i n t h e i i t e r n a s t a t e P o • ’

* w i . These changes c a n be c o n t r o l l e d f o r by running a

repea ted c o n t r o l (normal)

Figure 7 H and &f recruitment curves for . +

a typical - - normal subject

Figure 8 H and M recruitment curves for test

and control experiments with a - - - - -

typical subject t o show the g&phical

method of data analysis

response / s t imulus c u r v e s o r , where t h i s is n o t p o s s i b l e

( e .g . a f t e r a l c o h o l h a s been a d m i n i s t e r e d ) , by us ing t h e

M-wave ampl i tude a s a c o n t r o l f o r t h e H-wave.

For a g i v e n s u b j e c t , when d i f f e r e n t exper iments a r e

conducted on d i f f e r e n t d a y s , t h e response c u r v e s may va ry

due t o s m a l l e r r o r s i n e l e c t r o d e placement . The s t i m u l a t i n g

e l e c t r o d e is p a r t i c u l a r l y d i f f i c u l t t o r e p l a c e w i t h accuracy

s i n c e v e r y s m a l l changes cause d i f f e r e n t motor and s e n s o r y

f i b e r s i n t h e n e r v e to he s t i m u l a t e d , This is c o n t r o l l e d f o r

by running new normal r e sponse curves f o r each exper iment .

For d i f f e r e n t s u b j e c t s , t h e r e w i l l be d i f f e r e n t r e sponse

c u r v e s f o r t h e r e a s o n s s t a t e d above and because o f <I

d i f f e r e n c e s between t h e s u b j e c t s . The o n l y c o n t r o l iS t o run

normal r e sponse curves . The M-wave is n o t a u s e f u l

i n t e r - s u b j e c t c o n t r o l .

Having e s t a b l i s h e d c o n t r o l s f o r each exper iment , i t is necessa ry . t o choose comparable f e a t u r e s on t h e response curves . The most

prominent f e a t u r e is t h e maximum of t h e H-wave response (Hmax)

and t h i s is s e l e c t e d f o r measurement. The d a t a is t h e n analyzed

e i t h e r by comparing v a l u e s o f Hmax d i r e c t l y , Hmax (s) /Hmax (c) o r ,

by f i r s t normal iz ing by d i v i d i n g t h e Hmax by t h e cor respond ing

where M ( s ) and M(c) a r e H-wave ampl i tudes o b t a i n e d w i t h Hmax (s)

and Hmax ( c ) respect ive ly .

The quest ion t o be answered i s whether i n t h e experimental

s i t u a t i o n Hmax(s) i s s i g n i f i c a n t l y d i f f e r e n t from t h e re l evan t

c o n t r o l Hmax(c). Since each experiment muqt be compared with

i t s own con t ro l , the d a t a is normalized by d iv id ing by t h e

c o n t r o l value Hmax (c ) ( see Appendix B) . . - -

Data Analysis

The methods used i n d a t a a n l y s i s include t h e graphica l

method employed by Dietz (1978), t h e percentage method used by

F i she r , e t a 1 (1979) , maximum H-amplitudes, Hmax/M r a t i o s , and

histograms.

1. Graphical method: H- and M-amplitudes w e r e p l o t t e d aga ins t -

voltage on t h e same s c a l e f o r test and con t ro l . For t h e

f a t i g u e experiment, ,a graph of H- and M-amplitudes,

i n t e g r a t e d EMG (IEMG) and H/M r a t i o s w e r e p l o t t e d on

t h e same s c a l e aga ins t t i m e .

2 . Percentage method

Po ten t i a t ion = ( H ( s ) - H(c) 1 & H (c)

Depression = ( H ( c 1 - H ( s ) I x loo H (c)

H(c) i s con t ro l maximum H-amplitude.

- - -

3 . H-amplitudes: This method involved obta in ing t h e h ighes t '

t h r e e values of H-amplitudes f o r t h e test and comparing

them with t h e h ighes t t h r e e H-amplitudes f o r t h e con t ro l .

The t h r e e value method was bel ieved t o be more r e l i a b l e

than the peak value alone. Potent ia t ion o r depression was

determined by H(s)rnax/H(c)max (when i.t i s observed t h a t t h e

t h r e e peak va lues were g r e a t e r thafi 1, then t h e r e was

po ten t i a t ion ; if equal t o 1, no change i n r e f l e x w a s

reported; and if less than 1, a db$*ssion of r e f l e x was

noted.

4 . Hmax/M r a t i o : In this method po ten t i a t ion o r depression

was determined by considering t h e H/M r a t i o f o r both

con t ro l .and t e s t condi t ions thus

Po ten t i a t ion o r depression = (Hmax/M(s) )

where (s) i n d i c a t e s t e s t condi t ion

( c ) i n d i c a t e s con t ro l ,

5. Histograms: The H-amplitude values obtained

i n ( 3 ) f o r each experiment with each s u b j e c t were normalized

by d iv id ing by t h e corresponding con t ro l values. These were

then averaged and p l o t t e d a s a histogram i n Figure 17, where

t h e ba r s i n d i c a t e t h e s tandard devia t ions f o r each test, - - - - - -- - - - - - -

C

* Measurements

H- and M-waves amplit%des were measured from t h e peak of

the wave _ t o its - lowest poi-nt i r r e s p e c t i v e of t h e position__of_

t h e base l ine (Fig. 3 and 9 ) . The measured values w e r e i n

m i l l i m e t e r s b u t were l a t e r converted t o m i l l i v o l t s by making "

- -

use of €3ie E3TG s e n s i t i v i t y used.

The i n t e r v a l la tency period was measured from t h e beginning

of t h e s t imulus t o t h e beginning of the H-wave. This value was

obtained i n m i l l i m e t e r s and converted t o mil l iseconds by making

use of t h e EMG paper speed (Fig. 3 and 9 ) . - -- ---

The H-reflex w a s obtained with submaximal s t imulus f o r t h e

alpha motoneurone, and it appeared before t h e muscle response.

I n a l l b u t one s u b j e c t t h e H-wave d i d n o t appear below 40 v o l t s

of t h e s t imulus, In one s u b j e c t it occurred as l o w as 24 v o l t s

of s t imulus s t r e n g t h (Fig. 9).

. Figure 9 P r i n t o u t showing the e f f e c t on

stimulus i n t e n s i t y on the H and M

responses

The c h a r a c t h s t i c s of t h e H-wave depended- on t h e following

f a c t o r s : condit ion under test, st imulus vol tage and s u b j e c t ' s

s e n s i t i v i t y , e l ec t rode placement, EMG s e n s i t i v i t y , whether

s u b j e c t was relaxed o r tensed up, Ggle between t h e p o s t e r i o r

su r faces of t h e th igh and l e g ( t h e b e s t angle range used w a s

115 t o 125 degrees) , and the ankle angl; (midplantarf lexion

range) .

Normal

C

The ranges of H-wave'.amplitudes were between 0.2 and 1.5

m i l l i v o l t s with' t h e mean range between 0.4 and 1.0 m i l l i v o l t s

(Tables 1 and 4 ) . The Hmax/M r a t i o range was 0.46 t o - 3 . 8 0 .

The mean value of t h i s r a t i o was 2.24 f o r a l l s u b j e c t s able 2 ) . The &nax/max r a t i o had a rangelof 0 .22 t o b.69 and a mean value

1

of 0.46 f o r a l l s u b j e c t s able 3) . . The response curves f o r t h e !

a H-kef l e x and t h e M-wave o f ' a s u b j e c t a r e shown ' in Figure .7.

Force

4

Submaximal phas ic fo rces po ten t i a t ed t h e H-reflex b u t

maximal sus ta ined fo rces depressed t h e r e t l e x . The o v e r a l l

e f f e c t s of force - on the - H-reflex - - - and - t h e M-wave - - - a r e - - - shown - - - -- i n - - - - - -

Figure 10 f o r a t y p i c a l sub jec t . - - - - - - -- ----- -- - - - - - - - - - -- - -- -- - -

1.57 millivolts with a

(~ables 1 and 4) . The 10.6% for all subjects.

The H-amplitude range was 0.17 to I

- mean range of 0.44 to 1.34 millivolts - -- - A - - a -

mean potentiation of the H-reflex was

A* typical response curve with alcohol is shown in Figure 11.

The - f imax/~ range for alcohol for all subjects was 3

-

5.0 with a mean of 2.42 (Table 2). Thg Hmax/Mm&

0.63 to 0.87 with a mean of 0.77 for all subjects

ratio was

(Table 3).

Figure 10 H and M recruitment curves

with force -7

1. considered with control , -

2 . graded force

FORCE f kg )

54

Figure 11 H and M recruitment curves

w i t h alcohol campared w i t h the

Asp i r in

I n a l l b u t one s u b j e c t a s p i r i n d e p ~ e s s e d t h e H-reflex as

shown by t h e response curves -of a t y p i c a l s u b j e c t i n F igure 12.

The mean depress ion of t h e r e f l e x f o r a l l s u b j e c t s w a s 13.7%.

H-amp1 i-tde r a n g e fTab3es 1 and 4 ) , was 0.25 t o -1.2 5 rni31ivo~~s- - -

w i th a mean range of 0.32 t o 0.93 m i l l i v o l t s f o r a l l s u b j e c t s . '

The Hmax/M range f o r a s p i r i n w a s 0.65 t o 5.0 and a mean va lue -

of 1.80 (Table 2 ) . Asp i r in showed a range of 0.42 t o 1.6 wi th

a mean va lue o f 0.83 f o r a l l s u b j e c t s (Table 3) . .

Caffe ine

CaEfeine l&ered t h e s t i m u l u s t h re sho ld for t h e - - -

e l i c i t a t i o n af t h e H-reEIex i n a l l s u b j e c t s and i s i l l ~ ~ t r a t e d

f o r a t y p i c a l s u b j e c t i n F igure 13. The mean potentiation of

t h e r e f l e x was 18%. The 3-wave -amplitude range 5or c a f f e i n e

, (Tables 1 and 4) w a s 0.25 t o 1.75 m i l l i v o l t s w i th a mean range

of 0.54 t o 1.33 m i l l i v o l t s f o r a l l s u b j e c t s . The Hmax/M ratio

range f o r c a f f e i n e w a s 1.0 t o 3.0 and a mean of 1.94 f o r a l l

s u b j e c t s (Table 2 ) . The Hmax/max ra t io range was 0.32 t o 0.94

---A --

. , P

Localized Fatigue

\

~ o c a l i z e d f a t i g u e of t h e c a l f muscle; . r e su l t ed i n a

p o t e n t i a t i o n of t h e H-reflex and a depression of t h e M-wave 6

(Figs. 1 4 , 15, 16) . A p o t e n t i a t i o n of 9.3%' was recorded as a ' z

mean f o r a l l sub jec t s . The H-wave amplitude *?ange was 0-18- %Q ---- - - -

1.27 m i l l i v o l t s wi th a mean range of 0.54 t o 1 . 2 m i l l i v o l t s f o r

a l l sub jec t s (Tables 1 hnd 4 ) . The Hmax/M range was 0.53 t o

3.9 and a mean of 1.81 f o r a l l sub jec t s (Table 2 ) . A range of

0.51 t o 2.07 was obtained f o r Hrnax/Mmax r a t i o able 3 ) . The

histograms (Fig. 17) show t h e magnitude of t h e e f f e c t s of a l l

t h e t e s t e d agents on t h e H-reflex and t h e i r staridard devia t ions

( see Appendix C) ,

, . I n t e r v a l la tency time was measured a t supramaximal .vol tages

when H-wave depression w a s high. Measurement was taken i n t h i s

condi t ion because la tency values were c o n s i s t e n t f o r t h e s u b j e c t

and measurement po in t s w e r e w e l l defined. There w a s a la tency

range of 27 t o 32 mi l l i seconds with a mean value f o r a l l

s u b j e c t s of 29.71 mil$iseconds. H-latency w a s n o t a f f e c t e d by -- -- - - - - - --- -

- - --

any of t h e con=tiuxTs t e s t e d ,

Figure 13 and recruitment curves for

caffeine plotted with the control - - - - - -- -- -- - - -

Figure 1 4 Hoffmann re f l ex changes i n fat igue:

H aqd M wave response curves, - - - - - --

IEMG, and, H/M r a t i o

Figure Eoffmann reflex changes i n fat igue:

the ekperiment i l l u s t r a t e d i n Figure

was repeated w i t h the same subject

Figure 16 Pr in tou t showing the na ture t

of response in fatigue

ii 1 t

i

F i g u r e 17 i k

TABLE 1 Hmax RANGES

CONDITION RANGE

Normal 0 . 8 - 1 . 1 5

Alcoho l f .25-1.57

A s p i r i n 8.8-1 - 2 5

Caffeine 8.75-1.65

- -- F a t i g u e - - - - -07 88-& 0-M

CONDITION RAHGE

fformal f ,46-3,8@

Aspirin 8.65-5.0

Caffeine

Fatigue %,53-3.9

MEAN

1.a

1 . 3 4

0.93

1 . 3 3

1 2 ~ 7 - ~

MEAN

2 . 2 4

CONDIT~ON - RANGE Normal -

/' Alcoho l j

A s p i r i n

Caffeine

Fatigue -

mE 5 PATlCUE

PARAMETER 1

H-AMPLITUDE

B/W ratio

H-antpl itudc

I EHG

PERCENTAGE CHANGE

20-116

98-216

5 0 4 % - - - - -

38-55

\ W N RANGE

TYPE OF C H z NGE

I n c r e a s e

1 n c r e a s e

Decrease

I n c r e a s e

V. DISCUSSION

The Ef fec t s of Agents with Widespread Influence on the

Nervous System

The experiments indicate that the H-reflex i s a sensitive

quite different agents un the ~&rvous system. Because of this, t-

there is reason to expect that t h i $ r e f l e x can senre a s an

easily accessible .model for testing the general effects of

drugs on the CNS, Of course i ts use with each new agent w i l l

have to t>e considered separately. Further study is necessary - - - - - - -

to investisate the ef •’e& of different d&es w i t h the agents

t e s ted here. \

There w a s narked potentiation of the ffoffraannreflen and

the *response one h u u after subjects drank a 6 oz. glass of

m a t t % beer f 5% a1 mhof, about 0,012 percent blood

i n a l l s e e pp-

- cancen &tiat:- Tfte -g6tari iaiI-unwarrevea1d

L.

l i terature. ZAlW concentrations of alcohol have been shown to

- - -- --

e x c i t e f r o g nerve-muscle p r e p a r a t i o n s (Knutsson, 1 9 6 1 ) .

Curare-blocked n e u r o n u s c u l a r j u n c t i o n s o f a f r o g ' s s k e l e t a l

muscle have been t r e a t e d with a l c o h o l and an i n c r e a s e i n the

ampl i tude o f endplate p o t e n t i a l obse rved (Okada, and Adachi,

1962). Low, e t a f (1962) have shown that low c o n c e n t r a t i o n s

of a l c o h o l f a c i l i t a t e human neuromuscular j u n c t i o n s . I n - - - - --

c h o l i n e r g i c nerve-lzuscfe: p r e p a r a t i o n s , alcohol was shown by

Sachdev, e t a 1 (1964 ) to p o t e n t i a t e muscle t w i t c h e s . This

a l c o h o l i n t h e present stu&y, 0

I n a s i m i l a r way t o ca lc ium, a l c o h o l ,causes the r e l e a s e of

a c e t y l c h o l i n e from s y n a p t i c vesicles (Wallgren, and Barry, L

1970) ChoLinergic interactions of alcohol w i l l i n v a r i a b l y

affect sodium and potassim movements a c r o s s cell membranes,

causing g e n e r a t i o n o f spikes. This t h e r e f o r e mans that

a l c o h o l will cdntribute-in p o s t s y n a p t i c membrane depolarization.

iIence the increase in the ff-reflex may b e a t t r ibuted n o t on19 t o

the spinal cord excitability b u t also t o a neuramuscular

Aspirin

the .+wave i n all b u t one subject. This effect was r e v e a l e d by

the graphical and B-amplitude methods of data analys is . The

-ax, Emax/M and Hmax/Mmx ranges and means for a l l subjects ,

when compared with values f o r the normal subject revealed

depression but the mean of &nax/h%uax indicated potentiat ion of

the H-reflex. Thi s analget ic drug i s not only ant ipyret ic ,

but a l s o a potent pain k i l l e r , I t e l iminates pain by delressing -L---LL-L-p- - -- - - - - - -- - -

the pain f i b e r s and suppressing the production of polypeptides

(e . g. bradykinin) which actual ly cause the pain (Mountcastle,

inhibi t ing prostaglandin synthesis and release (Vane, 1 9 7 3 ) . '*

Probably it depresses the central nervous system by

prostaglandin inh ib i t ion . Again, since the M-wave decreases, B

the decrease of the B-wave could be due t o a neuromuscular

Caffeine

Caffeine caused marked potentiation of the H-reflex and r

die *response amplitude wits markedly increased i n a l l subjects .

These effects were revealed in aII rrethods used for data

analysis except the mean of RsannfEf ratio. The Eraax and

H=ax/BWax ranges en2 ~eans for a l l subjects indicated potentie-

effect was obtained by taking coffee (caffeine content about

f QO-150 mgj ,

Caffeine s t imula tes t h e c e n t r a l nervous system (Topliss ,

1 9 7 0 ) and thus causes p o t e n t i a t i o n of t b e H-reflSk. Caffeine 2

i n h i b i t s t h e hydrolys is of CAMP, has l i p o l y t i c a c t i o n s and

p o t e n t i a t e s the e f f e c t s of epinephrine (Tr iggle , 1970) . A l l

of these e f f e c t s of c a f f e i n e c o n s t i t u t e important f a c t o r s i n *

the c e n t r a l ac t ion of coffee o n -the H-reflex. A g a i n , as with---- - --

alcohol , it i s seen t h a t t h e H-reflex provides a s e n s i t i v e

i n d i c a t o r of CNS s t imula t ion .

The Ef fec t s of Agents with Local Inf luence

General

The experiments with f o r c e and f a t i g u e show t h a t the

H-reflex can serve a s an i n d i c a t o r of t h e gain of the - - - - -

s p e c i f i c sensory-motor r e f l e x a rc involved. Thus it should be

a useful t o o l f o r fundamental inves t iga t ions of motor c o n t r o l

and f o r c l i n i c a l eva lua t ion of lower rnotorneurone l e s ions .

Force

The e f f e c t of f o r c e on the H-reflex was similar to t h e

e f f e c t of voltage on the r e f l e x ( F i g . 10) . I n most subjects

as force became sustained a pronounced t a l l i n the H-wave

amplitude resu l t ed . The M-response, though unchanged i n one of

the s u b j e c t s , was genera l ly a f f e c t e d i n t h e same way a s t h e

H-wave (Fig. 1 0 ) . These changes were revealed i n t h e graphica l

and ampliMde methods of - da ta analys is .

observat ions on t h e e f f e c t s of fo rce a r e not easy t o

explain, One explanat ion is' t h a t t h e decrease i n t h e H-wave _ _ -_

could be caused r e f l e x i v e l y by the decrease i n t h e M-wave.

Fat igue

I t has been suggested i n the l i t e r a t u r e t h a t t h e r e a r e two

phases t o the buildup of f a t i g u e during a sus ta ined i sometr ic

con t rac t ion (Stephens and Taylor, 1972). I n t h e f i r s t phase 4 ,

t h e decrease i n f o r c e is accompanied by a propor t ional decrease z-

in the synchronous muscle ackior rpoter r t ia l (Pf-wavej whereas i n --

t h e second phase t h e fo rce f a l l s more quickly than t h e ac t ion

p o t e n t i a l . The r e s u l t s repor ted here a r e n o t m p l e t e l y

c o n s i s t e n t with t h i s . In our experiment t h e - t o t a l fo rce was

maintained constant ; presumably t h e bui ld up o f - f a t i g u e i n t h e

- i n i t i a l l y r e c r u i t e d u n i t s r e s u l t s i n ,decreasing fo rce and

a d d i t i o n a l motor units are r e c r u i t e d . T h i s accounts f o r t h e

observed inc rease i n the H-reflex. The decrease i n ~unpii tude ;*

f a t i g u e . These r e s u l t s show that the decrease i n M-amplitude

is r o u g h l a p a r a l l e l to t h e inc rease i n H-antplitude. This is an -.

indirect i nd ica t ion that i n our.experiment h e r e n i s parallel

decrease i n f o r c e and synchronous a c t i o n p o t e n t i a l , i .e . the

two phases observed by o t h e r workers cannot be seen i n our

da t a .

It has been .hypothes ized by o t h e r s (Merton 1954 ; Edwards and

Lippold 1956) t h a t t h e p r i n c i p a l mechanism of f a t i g u e i s the

impairment of the c o n t r a c t i . l e mechanism of t h e muscle,

pos s ib ly 'due t o ischemia, This would probably r e s u l t i n

f o r c e d e c l i n i n g more r a p i d l y than t h e a c t i o n p o t e n t i a l and

accounts f o r t h e second phase i d e n t i f i e d by Stephens and

Taylor (1972). Our d a t a sugges t s a r a t h e r l a r g e decrease i n

t h e a c t i o n p o t e n t i a l (I?-wave) throughout t h e development of

f a t i g u e a n d - t h i s sugges t s t h a t o t h e r mechanisms may be

involved. Other sugges t ions i n c l u d e , c e s s a t i o n i n c e n t r a l

. e 4 c i t a t o r y a c t i v i t y (Big land-Ri tch ie :c i ted i n Die tz 1978) ,

impairment of neuromuscular transrnissi'on (Stephens and Taylor ,

1972) and a drop i n s p i n a l motoneurone f i r i n g r a t e (D ie t z , --.

1978) . The H-reflex may be a u s 2 f u l t o o l t o i n v e s t i g a t e t h e s e - sugges t ions .

L imi t a t i ons and Future Work

This series of exper iments w a s explora iory ln n a t u r e and

the exper im=tal des l fgnhaddef i n i t e l i m i t a t i o n s : a) t h e r e

w a s no r e a l c o n t r o l of the s u b j e c t s t d i e t be fo re each exper iment

b) t h e experiments were performed i n the same order f o r each

s u b j e c t s o a learn ing e f f e c t cannot be excluded; however t h e

s e r i e s was repeated f o r one sub jec t and e s s e n t i a l l y i d e n t i c a l

r e s u l t s were obta ined , cf t he f a t i g u e experiments were

conducted with o n l y one sub jec t d) only one dose l e v e l was

investigated for e a c h agent tested, el the possible I

psychofogical e f f e c t of knowing the nature of t h e experimental

agents ( a l coho l , a s p i r i n and coffee) was n o t inves t iga ted by

repeat ing the experiments with a placebo, f) t h e H-reflex

experiments a r e n e c e s s a r i l y s e n s i t i v e t o many factors--l imb

angles , general a rousa l of s u b j e c t s , d i e t of s u b j e c t s ,

e l ec t rodes e t c . Consequently more r e l i a b l e d a t a would r e s u l t

i f more sub jec t s had been used s ince random v a r i a t i o n s would

tend t o cancel out . I n s p i t e of these r e se rva t ions we a r e q u i t e

conf ident i n the general conclusions we' have drawn and i n the

d i r e c t i o n of the e f f e c t s of s p e c i f i c agents.

In f u r t h e r work, a more e labora te experimental design could

be used to i n v e s t i g a t e the =e&lts of these experiments and

to use a wide range of doses for each agent. Probably the most

i n t e r e s t i n g direction fur further work i s i n the use of t h i s

VI . CONCLUSIONS 1

The H-ref lex changes o b t a i n e d by t h e - u s e o f t h e d r u g s i n

t h i s s t u d y i n d i c a t e t h a t t h e r e f l e x can n o t o n l y b e a n e f f e c t i v e

t o o l i n t e s t i n g t h e : e x c i t a b i l i t y o f t h e n e r v o u s sys t em b u t c a n

a l s o d e t e r m i n e t h e a c t i o n and e f f e c t i v e n e s s o f some d r u g s .

Q u a n t i f i c a t i o n i s p o s s i b l e i n t h e H- re f l ex s t u d i e s and t h i s

w a d d be an asset i n its d i a g n o s t i c u s e , I n a d d i t i o n t o t h e s e

g e n e r a l c o n c l u s i o n s , t h i s s t -udy h a s a l s o g i v e n new o r

c o n f i r m a t o r y e v i d e n c e of t h e c t i o n bf c e r t a i n a g e n t s on s p i n a l 1 r e f l e x e s . S p e c i f i c a l l y , a l c o h o l (0 .012 p e r c e n t b lood

c o n c e n t r a t i o n ) p o t e n t i a t e d t h e H-ref,lex and i n c r e a s e d t h e s i z e

of t h e musc le r e s p o n s e , c a f f e i n e ( 1 . 3 g c o f f e e ) p o t e n t i a t e d t h e

r e f 3 . e ~ and t h e d i r e c t auscle r e s p o n s e w h i l e a s p i r i n f f 8 grf

d e p r e s s e d bo th t h e r e f l g x and musc le r e s p o n s e . I t was a l s o

suggested t h a t e a r l i e r e x p f q n a t i o n s o f fatigue i n s u s t a i n e d /d

': B c o n t r a c t i o n s need t o be re-examined.

MEDICAL HISTORY a

Name :

Weigh t :

D a t e :

. Check ( x ) i f a n s w e r i s y e s :

' P a s t B i s t o r y :

Have you ever 'had2

R h e u m a t i c ' f e v e r

Heart murmur

H i g h b l o o d p r e s s u r e

Any. h e a 2 t t r o u b l e

Diseas'es o f a r t e r i e s

Var i c o s e v e i n s

P r e s e n t Symptons : . ' Have you r e c e n t l y had?

C h e s t p a i n s

S h o r t n e s s o f b r e a t h

H e a r t p a l p i t a t i o n s

Cough o n e x q r t i o n

Goughing, o f b l o o d h

Back p a i n

Lung d i s e a s e - S w o l l e n , s t i f f , o r

O p e r a t i o n s p a i n f u l j o i n t s I .u

I n j u r i e s to b a c k , e t c . Muscle or t e n d o n i n j u r y

E p i l e p s y

S p e l l s o f severe d i z z i n e s s

E x p l a i n :

Age:

Height:

Is t h e r e a good phys ica l reason n o t mentioned here why you

s h o u l d not p a r t i c i p a t e i n c e r t a i n types of physical activity, r h

even i f you wanted to? ,

Subject's. signature: -- --

P e a k H-Amplitudes -

Subject A l c o h o l ( A )

H a 1

2

\

-4 *

4

5

Mean Ratios

Aspirin f As) Caffeine (Ca)

S u b j e c t

No. 1

2

3

- 4

5

H e a n R a t i o s

Alcohol ( A ) Aspirin ( A s )

Third to the Peak 8-Amplitude ---

Caffeine ( C a )

Subject Alcohol (A) . Aspirin ( A s ) C a f f e i n e ( C a ) /

Mean R a t i o s

Mean R a t i o s (X ,Y ,Z )

C a t e g o r y A l c o h o l X 1 . 3 7 Y 1 . 4 7 Z 1 . 4 8 T o t a l 4 . 2 4 Mean 1 . 4 1

A s p i r i n 8 . 9 4 8 .95 0 . 9 1 2 . 8 0 8 . 9 3

C a f f e i n e 1 . 2 5 1 . 2 8 1 . 3 8 3 . 8 3 1 . 2 8

d squared -

1 2 3 4 5

sum

Standard deviation = Square Root of Variance = 0.16

BIBLIOGRAPHY

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Bishop, B., J o h n s t o n R.M. and Wash W . ( 1 9 7 0 ) : Changes i n a l p h a and gamma motoneuron e x c i t a b i l i t y w i t h r e s p i r a t i o n s . Arch. Phys . Med. R e h a b i l . 51: 383-390.

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' Braddom R.L. and J o h n s o n E.W. (1974 ) : H r e f l e x : r e v i e w and c l a s s i f i c a t i o n w i t h s u g g e s t e d c l i n i c a l u s e s . Arch. Phys . Xed, R e h a b i l . 55:412-417.

Braddom R.L. ( 1976 ) : H r e f l e x . Arch. Phys. Med. R e h a b i l . 57:407. - -- - -

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- -

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