,

Exerciseand Diabetes Dr Mac Robertson

Summaryt

MBChB,MFGP (SA)

A"fter tbe d.iscouentof insulin, exercise uas strongly promotecl as a cornerstorte in tbe treatment oJ' cliabetes. In tbe last two decades, our knowledge of the pbysiology and patbopbysiologt o.f exercise as uell as our understanding o.l'diabetes bas increased so tremendously tbat GPs meedto reconsider the prescription of exercise as a panaceafor all diabetics. Man.y of these neu concepts are analysed in tbis ctrticle and tbe practical implicnttionsfor the GP ancl llis patient summarised. Very useful, guid.elines and. recom menda I ions a re gi uen throughout.

Curriculum Vitae Dr LI Robertson studied at Cape Town University where he received the MBC|B in 1954. He did some post graduate training at McCord Zulu Hospital (Durban), at St M o n i c a ' s H o m e ( C a p eT o w n ) . r e c e i v e dr h e MFGP(SA) in 1975 and has been in Private Family Practicein Durban since 1957. He l-rasa wide interest in different fields of medicinc, and at thc moment still holds thc lollowing posts: Senior Medical Oflicer Diabetes Dept (Addington Hospital), Medical Director - Institute of Human Sexuality. He also makes time to serve on several committees. He is an elected member of the SA Medical and l)ental Council ar.rdgives time tO nany other committees serving the communitlr. Dr Robertson has presented many papeIS at Medical Conlerences, has publisl-red several scientific papers and contributed to two medical textbooks.

S Afr Fam Pract 1994; 15.4-A

I(EYWORDS: DiabetesMellitus; Physicians, Family; Exercise,Physical; Exerciseand Diabetes

Over the past decadewe have witnessedan explosiveincreasein the populariry of exerciseand training, which has become for the yolrng, (and indeed many not so young), an integral part oftheir recreationaland social activity. fu health-careprofessionalswe welcome this, as there is no doubt about the importance of exercisein promoting physicaland mental h e a l t h .a n d ,p e r h a p se. v e ni n preventing and helping to cure disease.t Due to its known blood-glucose

23

SA Family Practice |anuary 1994

Dr MacRoberrson lowering effect, exercisehas traditionally been recommended as an important component of diabetes management. Soon after the diseoverlof insulin, exerciservas strongly promoted as a cornerstone in the treatment of diabetes.' And fbr about half a century this dogmatic opinion appearedto be irrefutable. However, in tie last two decades, our larowledge of the physiology and pathophysiology of exerciseand training,t'' as well as our understanding of diabetes,has increasedtremendously. Consequently,we have had to revise our opinion that physical activity is a panaceafor all diabetic patients.1,s,6,7 It is evident that the effect ofphysical exertion differs fundamentally in Tlpe I and Tlpe II diabetics. Further, the prescription of physicai exerciseas a meansof improving metabolic control should now be regarded as obsolete. Even in Type II diabetics,the resultsfrom a number of elaborateirrvestigarions are disappointing with regard to the beneficial efFectsof physical activity on glucosetolerance. llowever, this must not Iead to the conclusion that Type I and many Type II diabetic patients should not be advisedto e x e r c i s e .I n d e e d ,d i a b e t i cp a t i e n t s should be encouragedto exercisefor the samereasonsas the non-diabetic p o p u l a t i o n . O u r t a s ki s t o a i m a t teaching diabetic patients how to reduceor preventany exercisc associatedcomplications. And this demands a knowledge and understanding of the current conceptsofthe physiologicaland pathophysiologicalmechanisms involved in the reeulation of fuel

5A Htrirartspraktlk Iarruarie I aq4

.. Exercise andDiabetes .' ::: ,. Table l: Effectsof short-term and prolonged exerciseon hormones.

homcostasisduring exercrse. The successftllperfbrmar-rce of exerciscrequires a drastic increaseof energy and oxygen sr-rpplyto the u'orking muscle whilst, at the same tirne, maintaining adequateenerg). and oxygen suppiy to the brain and other vital organs.

ShCIrt'tbffi

., :.

::t'

Catechotamines,

'

-a'

,a

: LOTUSOI :::

i

-' r:, ,

N/C or :

Glucason

N/c ' - f

-

: .. -=deCreaSed. NlO *'unehflnged.+=lncreased. .

a.

production may cven exceedthe rate of glucosc-utilisationand blood glucosc rnav increase. 75% of hepatic glucoseoutpllt comes fiorn glycogcnolysis,the rest from gluconeogenesis.

Glucose

: .:l t.

:::

CoLutter-regulatory

Liver

N1C or + .'' , NfC or +-

''t-'

ata

Gluctrse Hdimonal iegulaiion ofPlasma durins iitr;J I

O

-..

I

Growh Hormone

l)lrring the first 5-10 minutes of exercise,muscle glycogen is the main sorrrcc'of energv,but as exercisc continues, giucoseand non-estcrified fatty acids (NEFA) become increasingll.importalt, and with prolonged exercise,NEFAs become the major fuel. During the frrst hour of exercisc blood-glucose lo,els rerlain virtually unchtrngedbecausehepatic glucose production riscsto meet the needsof the exercisir-rg musclc. With strenLlousexercisehepatic glucose

:t.

Insulin

Effects of acute exercisein the non-diabetic(seeFigure 1)

Prolonged

tt

O

l)uring prolonged exercise,a nondiabetic's insulin secretiondeclincs and the rcleaseof counter-regulatory hormones ( glucagon, c()rtisol, gro$th-hormone, adrenalir-re and nor-adrenaline)increases.However, despitethese protective mcchanisms, ifexercise lastsfor severalhours, hepaticglucoseproduction mav not keep pace and blood glucoselevels decline. HJ)pogl.ycaemianta.vfollor,r'2 to 3 hor"rrs of continuouscxercise without caloric intake.' Again, this is in the nonnal sublect. Furthermore, ifthe exerciseis precededby a large sucroseload causinghyperinsulinaemiawhen the exercisebcgins, then hlpoglycaemia may develop as littlc as 30 minutes after exercisebesins in the non-diabetic.o

Insulin Manl, cndocrinc changesoccur during cxercise.(SeeTablc l).

24

SA Farrilv Practicefanuan'1994

S A H r r i s r r t s p r r k t t kI r r r r r r r r c1 9 9 4

... Exercise andDiabetes Effects of physical training on glucosemetabolism Highly trained athletes have low fasting plasma insulin levels and reduced insulin responseto a glucose challenge,suggestingnot only hepatic, 6ut wbole-body sensitivity to insulin. Conversely, even a few days' immobilisation can markedly impair glucosetoleranceand insulin sensitivity.'o

Effects of physicaltraining on lipid metabolism Physical training renders lipid and lipoprotein profiles lessatherogenic. Serum HDL cholesterollevels increasewhile total cholesterolIevels remain unchanged or decline.tt Serum triglyceride leveis may also decrease.

Effects of exerciseon diabetics Insulin -clepe ndent cliabetics The metabolic and hormonal responseto exercisein IDDM p a t i e n t si s d e t e r m i r r e db y m a n l factors,such as the intensity of the exercise,the patient's level of metabolic control, the qpe and dose ofinsulin injected before the exercise, the site of the insulin injection, and the timing of the previous insulin injection, and meal, relative to the exercise. Accordingly, blood gh.rcose concentrationscan decline (most commonly) or increase,or stay unchanged. The major determinant is the availabilityof insulin, bearing in mind that insr"rlinlevelsdecline in non-diabeticsduring prolonged exercise.

Hyperinsulinaemia may occur for severalreasons. First, short-acting insulin injected a few hours previously may exert its peak action during the exercise. This is exaggeratedif the previously injected limb is exercisedD . uring hypoinsulinaemia, the inhibitory efFectof insulin on hepatic glucose production and its stimulatory effect on glucose uptake by the muscle are both reduced. In addition, the counter-regulatory response

Prescribingphysicalexerciseas a means of improving metabolic control, is now obsolete

(catechoiamines,gh-rcagon,gro\\th h o r m o r r ea n d c o r t i s o l )t o e x e r c i s e is higher than normal in insulin deficiency,t2giving an overall result of hyperglycaemia. Increasedlipid mobilisation and ketogenesisin the liver increaseblood ketone body concentrations. Thus, the hypoinsulinaemic patient may become ketotic and hyperglycaemic following exercise. Flar.ing said this, one should emphasisethat many Type I patients successfullyundertake the most strenuoussports like the Comrades Marathon, or Triathlons, provided that both diet and insulin dose are adjusted appropriately before and during exercise. After prolonged exercise,patients may have hypoglycaemic symptoms which may last into the next day due to persistentlyenhancedglucoseuptake 25

SA Family Practice lanuary 1994

by the exercisedmusclesto refill glycogen stores. Non-insulin-dependent diabetics These patients characteristicallyhave both hepatic and peripheral insulin resistancein the fasting state. During acute exerciseperipheral glucose uptal(e rises rnore than hepatic glucoseproduction and blood glucoselevelstend to decline.t3 However, at the same time plasma insulin levels fall so that the risk of exerciseinduced hypoglycaemiain NIDDM patients is small, even during prolonged exercise.'nIf NIDDM patients perform strenuous, glycogen-depletingexercise,both peripheral and hepatic insulin sensitivity are increased and remain increasedfor 12-16 hours after exercise.t'

Effects of physicaltraining in diabetics Insulin -dependentdia betics Most IDDM patients are insulinresistant. Physicaltraining in these patients improves whole body insulin sensitivity as it does in the nondiabetic but will only improue metabolic control if tbe training programme is accompaniecl by blood-glucose monitoring and, appropriate cbanges in diet ancl insulin in order to preuent bj,poglycaemia and reactiue bl,perglycaemia during and after exercxse. fu in the non-diabetic we get the beneficial lipid changes as well as the samedesirablepsychologicalbenefits, particularly in diabetic children, S A H u i ' r r t r p r r k n k l r n u . r r i e1 9 9 4

.. Exercise andDiabetes in NTDDM, js 31'*l?9*:,,:ractor

:gxrhcanrly lessin older athletes rhan

sothatotder li^111"":.Vsubjects,

incid.n.. it-r1:;il"i:fl;;;,'"eilehandedsairing,rnoror.racins,(danger oi' ffi;'ffilfX" alower

jornacffi,ponn^r,. Kf#:,x:x{?iw'.*retinopath

rorexercise rlffiffi :ndations

if-',u*iiiffi;.ff'

f,ffi:#:ffffnTi*ff t#i,,#*,* nl

t'enerallli diabetics

*{flii'{ruff:'ffff*i? j[J::r *;1;:,":,j: r'J :j:[]'

rernember:

:*qd

l^llf?utrg" my diabeticsto plrrropare in just about wrrh few.exceptions. a.llsporrs, Tl," g;j"il", jj:: Ilbl: 2) rnustbe taitored to the

*c en, :#i3ff y ffl*i:'.*::':,j';*:: ::*, ffi.'Jii',':'.L:?,.;I :::i' Tfi ::T Aillli:#

ntness'and to increase exercise ;r;;;-*#.t

individualneeds and

Lo[:"'*

toexercise

, i[!*:Eiiwi;l* sor

glycaemicnu.tu.tili

improvcdfl.clings lilldtlt b.ettcr of wcil_ acccptance (bypeers ::1F, alrd tanrill.),

and greaterself_estcem.

Non insulin_cleben

n,betics nnu.'..i,.,,,j,: {;:ifr:,c/

fii'ff"-"ff :';:j"; ;;"d.; i:iJ"H a'0, o ;lJ"".?f ::ffiil::fl :',1.1".,T'. ::,?,L iiit T,lf,:,i.::::, trainingin NrDDM lft-olurt:at has beenreporredro

::ji*,r

coronary risk fhctors

y,,ffi i[:l[rli'iff::; $j[t4]::i,..,,L?ff:*tl il,': h". fli:iifl#::Ll1'#f.'.'*$:' 1l

prophylacticu.lu" of-""".cise will be youngerpatien rs wirhou i.l^1,::,tn t csrablrshed atherosclerosis.

ru;i?,uu:*r, :Jjj ;ffi:;i,:l "o

l,ii;*.1.1 "', :il il:i::T:il y i:: 3l?ilT.*:

wrth high C_peptide li.rJ:",: reserve insulin resistance j:::.. rarher rnsu_lrn depletion is responsibJethan for rneir diabetes) oral 6rucos€ elu, tolerance is alsoimpro";J'*

*1:l:tr. drabetes

irr the prevention of

cannorprevcnr rhe .L::.:0. i t>oM but regutar ,l.l^t.",gonr"nr,rt mayprevenror detayrhe ::j::r. manrtesrarion of NIDDM in-prrin* r""1* genedcpredisposition. rL,j,I,,1_rcsisranc.. nsulrn thai irnportrni"... 26

,t-e] ;i nhrc;;,.#iliffl"J?^"

SA Familv practicc

Januarv 1994

Diabetic patients

should the same reasons as :::..j::,Jbr non-diabetic pattents

ff,'TH".* filt:i!,:::;ff is r i:,""t*:nrrshone

ruil

1,,;;ry5;Tlffi#r#

wrthout marked ur_a_ T::1,"T" glucose variadon.

SA Huisartsprakq,k

/anuarie 1994

... Exercise and Diabetes Diabetes Metab Rev 1986;'2: 53-68.

hour$. : ::::, .::: :i:ii: 'it::

7. Berger M, Kemmer FW. Discussion: excrcisc, fitness and diabetes. In Bouchard C, Shcpard RJ et al, (cds). Exercise, fitness and health: a consensus ofcurrent knowledge. Champaign IL: Human Kinetics Books. 1990: 49I-95. 8. Felig P, Cherif A, Minagawa A et al. Hypoglycaemia during prolonged exercise in normal man. N Engl J Med 1982'306: 895-900. 9. Koivisto VA, Karonen S-L, Nikkile EA. Carbohydrate ingcstion before excrcise: comparison ofglucose, fructose and sweet p l a c e b o . ] A p p l P h y s i o ll 9 8 l ; 5 1 : 7 8 3 7 .

T7 Ruderman NB, Ganda OP, fohansen K. The effect ofphysical training on glucose tolerance and plasma lipids in maturity onset diabetes. Diabetes 1979;28 (suppl l):89 92.

I 8 Skarfors ET, Wegener TA, Lithell H ct al Physical training as treatment forType2 (non-insulin-dependent) diabetesin elderly men. A feasibility study over 2 years. Diabctologia 1987; 30: 930-3.

t9

SealsD\ Hagberg JM, Allen WK et ai. Glucose tolerance in young and older athletes and sedentary men. I Appl P h y s i o l1 9 8 4 ; 5 6 : I 5 2 I - 5 .

I0. Koivisto VA, Yki-Jarvinen H, DeFronzo R. Physical training and insulin sensitivity. D i a b e t e sM e t a b R e v 1 9 8 6 ; I : 4 4 5 - 8 1 . I I . Huttunen ]I( Lansimics E, Voutilainen E et al. Effect ofmoderate physical exercise on serum lipoproteins; a controlled clinical trial with special reference to scrum highdensity lipoprotcins. Circulation 1979 ;

60:1220'9.

References: l. Smith T. Exercise:cult or cure all! Br Med I I983; 286:1637-9. 2. Katsch G. Arbeitstherapie der Zuckerkranken. Erg Physikal Di€t Ther 1 9 3 9 ;l : I - 3 6 . 3. Vranic M, Berger M. Excrcise and diabetes mellitus. Diabctes 1979; 28: t47-67. 4. Kemmer FW, Berger M. Exerciseand diabetcs mellitus: physical activity as a paft of daily lile and its role in the treatment of diabetic patients. Int f Sports Med 1983; 4:77-88. 5. Kernmer FW, Bergcr M. Exercise in therapy and the lile ofdiabetic patients. Clin Sci 1984; 67: 279-83. 6. Kemmer FW, Berger M. Therapy and bctter quality of life: the dichotomous role of exercise in diabetes mellitus.

12. Berger M, Bcrchtold P, Cuppers HJ et al. Metabolic and hormonal effccts of muscular exercisc in juvenile typc diabetes. Diabetologia 1977 ; 13: 355-65. 13. Minuk HL, Vranic M. Marliss et al. Glucoregulatory and metabolic response to exercise in obese non insulin dependent d i a b e t e s .A m I P h y s i o ll 9 8 l ; 2 4 0 : 4 5 8 64. 14. Koivisto VA, DeFronzo RA. Excrcise in the treatment oFtype II diabetes. Acta Endocrinol 1984- 262 (suppl): 107-I l. 15. Dcvlin fT, Hirshmen M, Honon ED ct al. Enhanced periphcrai and splanchnic insulin sensitivity in NIDDM mcn after a single bout ofexercise. Diabetes 1987; 36: 434-9. 16. Schneider SH, Amorosa LF, Khachadurian AK et al. Studics on the mechanism of improved glucose control during regular excrcise in Type 2 (non-insulindependent) diabetes. Diabetologia 1984; 26:355 60.

28

SA Family Practice |anuary 1994

SA Huisarsprakrykfanuarie1994