chudyk et al 2011 effects of exercise on cardiovascular risk factors in type 2 diabetes

8/3/2019 Chudyk Et Al 2011 Effects of Exercise on Cardiovascular Risk Factors in Type 2 Diabetes

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Octobe r 2009 and studies published asfu ll reports m the English language.References of relevant review artIC lesand tnals were screened to identify articles thai were nOI found th rough thedalab:lsc sc:lrches.Inclusion alld exclusion criteriaThe study populations consisted of indiVIduals aged ;2! 18 re ars who have a diagnosis of type 2 diabetes and are engagmgIn a structured exercise program consisting of aerobic exercise, progressive RT, orcombmed aerobic and progressive RT.Because we were interested m exercIseprograms Ihal had the potential to meetthe American College of Spons Medicine's recommendation that individualswith type 2 diabetes expend a minimumcumulative IOtal of I ,000 kca l per week ofenergy from physical acthi ties. fomls ofexercise Ihal did not meel lhis definttlon(i.e., taH:hi) we re not included. To be mcluded, the exercise mtervenllon had 10be quantifiable m terms of frequency, In -tenslly, time, and duralion. Only studieswhose treatment was allocated uSing arandomized procedure and whose control group was nO! prescribed exercise aspart of the study were eligible for inclusion. Because HbA k reOecls the :J.\"erageblood glucose level during the precedmg8--12 weeks, and gwen that we were interested In the effects of sustained exerciseas opposed to aCUle bou ts, we only included trials In which the exercise mtervention had a minimum duration of 8weeks. Finally, we only included studiesthaI measu red at least one of the followingoutcome measu res.Outcome measuresThe chronic hyperglycemia that chamctenzes type 2 diabetes is related to asignificant long- term sequelae, includingdamage to and e\'entual failure of vanousorgans (macrovascular). and dIrectly related to the ltkelihood of developingmicrovascuklr complications (8). Therefore. our pnmary outcome measure wasHbA le , which nOI only provides an estimate of overall control of blood glucoselevels within the preceding 8--12 weeksbut also is considered the gold standtudfor measunng long-term glycemIC control(8. 16).

Our secondal)' outcomes mcludeddyshpldem13 (HDl cholesterol]C]le\'els,l Dl-C levels, triglyceride levels), systolicBP (SBP). EMI. waist circumference, andweight. Alt hough there is Strong evidenceto support the notion that improvedcarc.diabelcsjournals.org

glycemic control reduces the risks ofmIcrovascular complicatIons. a relationship between improved glycemIC controland reduction in macrovascular complica\Ion has nOI been demonSiTated throughrandomized controlled tnals (S.16).Therefore, our secondary outcomes included dyslipidemia, a condition that iscommonly charactetized In patients withIype 2 diabetes by the Matlierogenic lipidt n a d ~ of h}'pcrtriglyceridemla. low levelsof HDl-C, and a predominance of small.dense, lD l -C particles (17) and that hasan established relationshIp with risk ofmacrovascular comphcal1ons (S). SSPis a marker of hypertension that has ast ronger association with risk of CVOand ren al disease than diasto lic DP(DBP) {IS}. ObesllY is a prominent riskfactor of type 2 diabetes, With an estimated S6% of individuals with Iype 2diabetes bemg o\'erwelght or obese. ofwhom 52% are obese and 8.1 % aremorbIdly obese (19). Moreover, obesityis an mdependent risk factor for CVO(20), and weight loss among patientswllh diabetes is often associated withreduced clinical symptoms and mortality nsk {2 1}. Therefore, our secondaryoutcomes included BMI and weightas measures of changes m body com position.Statistical analysisStatistical analysis was performed uSingRev iew Manager 5 soft ware (RevMan5.0.17, Cochrane CollabomlLon, Oxford,U.K.). For continuous outCOlnes presented on the same scale, we use d aweighted mean diffcrence (WtvID) calculated using the final follow-up P va lues provided for the interven\lon and controlgroups to anal}rze the SiZe of the interventioneffecLS. \Vhen continUOUS outcomes werenot presented on the same scale, Sland'ud!Zed mean differences (SMDs) were used 10anal}'%e the size of the mten'enlion effecLSfor the inten'ention and control groups alIhe studies' last reponed end pomts. In theevem that stud}' outcomes were presentedas change scores, the first author of thestudy was contacted with a request for prepost data. Studies whose authors did notrespond \\ithin I month's lime or whoseprepost data could not be obtamed fromthe Cochrane Collabomtion's library of reviews (13) were excluded (22,23). All datawere initially analyzed wuh a fixed effecLSmodel. A standard -i test was used to assess the presence of helerogeneity betweenstudies. \\ilh an 0: significance level of 0.05used as an indicator of the presence of

Chlldy k and PI,.clfasignificant heterogeneuy. The degree of inconsIstent)' among stud}' results wasestimated usmg the 11 parameter, wherean 12 parameter >50% was consideredindicative of substantial heterogeneity.Where heterogeneity was found, the analysis was redone using a ran dom effectsmodel.RESULTS- In Ihe mitial search of thedatabascs. 645 amcles we re initially identified. The most common reasons forexcluding articles were lack of a noexercise or standard care control group:exercise mten'enl1on could not be quantified in terms of frequency, intensity,dumtion, and \lme; study im-estigatingthe effects of aCllle exercise; wrong studydesign: and irrelevant study population.A total of 34 amcles were mcluded In thereview, wuh two studies (24,25) including three treatment anns (a combmed aerobic and RT arm, an aerobiC exercIse arm,and an RT arm) and one study (26) tn eludmg twO treatment arms (a combmedae robic and RT arm and an aerobic exercise arm). Therefore, 21 studies (24-26,Supplementary Refs. 51-518) reportedoutcomes on the effects of aerobic exercise. eight studies looked at the effects ofRT (24,25, Supplementary Refs. 519-524), and 10 studies reported on theeffects of combmed ae robic and RT mtype 2 diabetes (24-26, SupplementaryRefs. 525-531). Four studies reportedresults through separate pubhcal10ns(Supplementary Refs. 51-53,512, andS13).Characteristics of included studiesAerobic exercise . The majority of studies(21 studies) mc1uded tnvestigated theeffects of aerobic exercise among patientswlIh type 2 dmbetes (Table l) . The frequency of prescribed exercise rangedfrom a minImum of one to a maxImumof sewn sessions per week, with 13 of thestudies prescribing exercise 3 days perweek. Exercise mtensity was reported mterms of percentage of VOz max, V0 2peak, or maximum heart rate (HR): onestud}' reponed exercise intensity in termsof kilocalones expended per week. TheintensllY of exercise mnged be tween 50and S5% V0 2 max or V02 peak and 55and 85% maximum HR. length of exercise sessions ranged between 40 an d75 mm, and dur.mon of exercise mler\'ention ranged between 2 months andI rear.RT . All eight studies looking at the effectsof RT (Table 2) invoked three supervisedDIAIIETE5 WR(, VOlIJME 34. MAl 2011 1229


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Exercise tIIlll C(lrd iowlSCII ltl r risllTable 1---Cll(lr(lCIC riSlk s of (llI'obic exercise /rials

StudrKaplan et aI. , 1985

(Supplemental), Ref. 57)

Ronnemaa et aI., 1986 and1988 (lipid results for 1986stud}') (Su pplementaryRefs. 512 and 513)

Wmg et a1.. 1988(Su pplementary Ref. 515)

Razetal.,1994(Supplemental)' Ref. 511 )

Ugtenbcrg et al., 1997(Supplementary Ref. 58)

t-,-Iouricr et aI., 1997(Supplememal)' Ref. 510)

Boudou et al" 2001 (lipidresults) and 2003(Supplementary Refs .SI and 52)

Cuff el aI., 2003 (22)

ImervemionDiet \' S , exercise

(walking) \'5. diet +exercise I'S. control

Exercise (wal kmg, Jogging,or skiing) \'S , control(no mstruCllons re : exercise)

Diet + exercise(walkmg) 1'5. diet

ExeTCIse (bicycle,treadmill, rowmgmachine) \' 5 . control

Aerobic exercise (e.g .bICycle ergometer,SI\1mmmg, rowing) I'S,no exercise control

Training + BCAA supplement1'$, naming + placebo 1'5,sedentary + BCAA supplemelll\'s. sedemal)' + placebo

Continuous + imermillentexercise 1"$. control (exercisedon ergomet("T at a constant mteof 60 r,p,m, for 20 mm at lowintensitr [30 WI)

Aerobic (treadmill, bicycle,recumbem slepper, ellipl1ca1trainer, rOl11ng machme)\'5. combmed aerobiC + PRTI"S. control (usual care)

1230 DIABETES CARE, VOWM{ 34 , M oll' 2011

Frequency. Imensay. I1mc . dural10nExerCise group: 8/10

sessions: 1 sessionsunknown

F: I day/weekI: 60-70% maxT: iO-6O mmD: 10 weeksF: 5-7 S("sslons/weckI: 70% Val maxT: 45 mmD: 4 monthsF: 4 days/weekI: -1.561 kcallweekT: 3 mllcslsesslOnD: 10 weeksF: 3 days/weekI : 65% of maxT' 60 mmD: 12 weeksF: J days/weekI: 60-80% Val maxT: 50 mmD: 26 weeksPretr;unmg period. then:F: 1 dayslwrekI : 75% of peak supcr.'ised45,mm qehng class

plusF: I day/weekI : 5 exercises at 85% of V02p e ~ k (on an ergoq-cle)scparated by 3 mill ofexercise at 50% VOl peak.Both for :

D: 2 monthsF: 1 days/weekI: 75% of V0 2 peak super.'lscd

45,mlll cycling classplusF: 1 day/weekI: 5 exercises at 85% of V02 peaksepamted by 3 nun of exe rciseat 50% Val peak.

Both fo r:D: 2 monthsF: 3 days/weekI: 60-75% IiRRT: 75 millD; 16 weeks

AdherenceDirectly super"scd:

log book

Exercise dianes

314 dars superVisedfor first 10 weeks

213 directly supervisedsessions/week

Supcr.'ised group exerclSCfirst 6 weeks, thentmmmg:ll home:log book

D l r e c t super.'lscd

Directly supervised

Direc tly supel"o1sed

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able I-C OIu iuliedtudy

Van Rooijen et aI., 2()(H(Supplemental)' Ref. 514)

MiddlebrookI' et aI., 2006(Supplemental)' Ref. 59)

Brassard et a\., 2007(subjects ha\'e LVdiastolic dysfunwon)(Supplementary Ref. 53)

Kadoglou et aI., 2007(Supplemental)' Ref. 55)

Kadoglou et al.. 2007(Supplementary Ref. 56)

Igal Ct aI., 2007 (2 4)

Brun et al.. 2008(Supplementary Ref. S4)

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InterventionHome exercise (walkmg) +hospital-based aerobics VS.control (relaxation exercises)

ExerClse \"s. no exercise control

Exercise (bicycle ergometer) \'s.control (no aerobicexercise or RT)

Exercise (mamly cyclmg.treadmill walking/running.calisthenics) \s. control(mamtain habuual actl\lties)

Exercise (treadmill, cycling.calisthentcs) \'s. control(mm ntain habitual aCtl\l!les)

Aerobic (treadmIll , bicycleergometer) \'5. RT vs.comhmcd \'5. control

Exercise (walkmg,joggmg.or gymnastics) \'5 . control(rout ine care)

Frequency, intensity, ume, durationHome exercise:F: 2X/dayI: moderate RPE of 12-14(-somewhat hard" on

Borg scale)T: stan at 10 and work up to

45 min/sessionD: 12 weeksHospital ae robics:F: 6 sessionsI: 55-69% max HR

(RPE 12-1 4)T: 45 mmD: 6 sessionsF: 3 days/weekI: 70-80% max HRT: 30 mmD: 6 monthsF: 3 days/weekI: 60-70% VOz ma xT: 30 mmD: 12 monthsF: 4 days/weekI: 50--85% VOl ma xT: 45-60 mmD: 16 weeksF: 4 days/weekI: 50-75% VOl peakT: 45-60 mmD: 6 monthsF: 3 days/weekI: start at 60%, work up to

75% ma x HRT: start at 15 min, workup to 45 minD: 22 weeksI-month educational penod

(8 2-h sessions OVCT4 weeks): I h of exerciseeducation + I h of learningto cycle at ventilator thresholdfor 20-45 min.

Then:F: 2 days/weekI: at the level ofthe ventilalOl)'

thresholdT: 45 min/sessionD: 11 months

Clllldy lt mill Pelrel lCl

AdherencePhysical activity log:

atlendance log

2 days/week of supervisedgroup exercise: fiued with HRmonitors 10 ensure correctintenslt), and duration

Directly supervised

Di rectly superVised

Directly supervised

SupervIsed weekly for fi rst4 weeks. bIweekly thereafter:logs: ldenufication scanningat gym: HR monttors

Actint}' log: HR mOntlOr10 ensure correct trainmgintenSIty

DIASHES CARE. VOLUME 34, (1, 1..1, 2011 123 1


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Exucise alld cardio\'Uscular riskTab le l-Conl inued

Inlerventlon FrequenC)'. InlenSLI)'. ume . durmion Adherencelambt'rs el aI, 2008 (26) F 3 da)'s/week DIrectI)' supe rvisedombmed endurnnce ..stre ngth tr:l1nlOg (CIrcuIt)

\'5. endumnce (simIlar tocircu ll-same mtenSltybut no strength tmmmgexerclSCs) \' 5 control

160-85% max HR; RT: Slaned al60%, mcreased 10 85% I RM .

NOJlma et al. 2008(Supplememal)' Ref. S17) AerobIc tr:l1nlOg (suggestedwalkmg. JOggmg, c}"chng,5 ...1mmlOg) \'5 comrol(routme care)

AerobIc Imlnlng (walking!

3 selS or 10-15 repsT 60 mm/sesslono 3 monthsF al least 3 days/weekI nOI staledT al least 30 mm/seSSlonD.12momhsF 4-5 days/week

Not assessed

HR monuors; at least}"cherle)' el aI., 2008(Supplementary Ref. S18) Joggmg) .. caloncresl riCllon \s. caloricreStrlCIIOnI 60-65% HR max Increasedto 75-80% HR max byweek 12

I dIrectly su penisedsession/weekT 25-30 mIn/sessIon mcreased

10 55-60 mm/sesslon brwtek 12o 12 wttksSCM. br.mchcd-chaln amino acid, D, duranon, F. frcqutnc)': HRR. hc-an nlf restlVC. I. InICOSU)'. l \'. Jefl \cmncular. PRT. pmgrCl$lvc lT$IStancc lnlning. rcps.rcpcll1l0ns. RM. rcpClIlIon maximum. RPE. nllng of PCTCCI\'Cd cxcnlon. T. lime

exercise sessIO ns pe r week. wIth the studyby Sigal et al. (24) switching to biweeklysupervised sessions after I month of su pervised traimng sessions. Exercise duration varied between each interventIon andranged belween 8 weeks and 6 months.Exercise Intenslt)' ranged between 50 and80% one repetition maximum among thestudies.Combined aerobic and RT . Ten studieswe re seleCled for inclusion wuhm thiSexercise category (Table 3). The majornyof the studies directly monitored the compliance of the subjects with the exerciseprotocol for al least one session per week.with one stud)' switching to btweekly suopervised exercise sessions after 1 monthof traming and one stud)' rel)'mg on aclIVII)' logs to momtor patient adherence tothe exercise protocol. Six of Ihe studiesmvolved an exercise program carriedout three times per week, two studies involved tWO weekI)' sessions, one study in\'oked four weekly sessions, and onestudy involved a goal of partiCipants engaging In exercise 5 da),s per week. IntenSity of the prescribed aerobIc exercise\'aried between an initial exercise intenSll)' of 35% HR maximum 10 an upwardmaximum of 85% HR max . The reSIStance component of the interventionsvaried in terms of prescnbed load, repetition, and number of se ts. Duration ofthe imer.'emions ranged belween 8 weeksand 24 months. with nine of the ten1132 DV,8f.TES CARE. VOLUME 34 , MA Y 201 1

slUdles havlIlg a duration of al least 3months.OutcomesHbA lc' AerobiCexerCIse reduced HbA lcby 0.6% (-0.62 HbA tc WMD , 95% CI -0.98 to -0.27). RT alone was not foundto ha\'e a stausl1call), stgmficant effecton HbA lc (-0.33 HbA lc WMD , 95% CI-0.72 to 0.05). Combined aerobiC and RTreduced HbA lc by 0.67% (-0.67 HbA lcWMD. 95% CI -0.93 to -0.40). whichIS conSidered both stallsllcally and chnicall)' significant.D),slipidemia. Aerobic exercise was notfound to ha\'e a significant effect on HDLe ( -0 HDL w ~ 95% C1 -0.05 100.05) and LDL-C (-0. 10 WMD , 95% C1-0.44 to 0.24). Howe\'er. aerobiC exercise was related to a 0.3 mmoVL decrease(-0.29 WMD , 95% CI -0.48 to -0.11)In tnglycerides . Estimates of the effects ofRT on HDL-C and LDL-C WeTe nOl madebecause on I}' twO slUdies in\,esugaledIhesc outcomes. Because only Sigal et al.(24) im'estigated the effects of RT on triglycende levels, a summaI)' of effect wasnot calculated for thiS outcome. Combilled ae robIC and RT was nOI found toha\'e a sigmficant effect on HDL-C (0.05HDLC WM D . 95% C1 -0.05 to 0.15)and LDL-C (-0.07 LDL-C WMD , 95%CI -0.25 to 0.1l), but lowe red triglycerIdes by 0.3 mmoVL (-0.30 triglyceridesWMD . 95% C1 -0.57 to -0.02). The

numbe r of tnals in this anal)'s is wassmall.Bod y composition. No statistically significant relauonships were found betweenan}' of the exercise categories and changesin B ~ I I or bod)' mass; because only oneRT slUdy reponed BMI as an outcome,estImates of effecl we re not calculated forBMI wilhm this exercise category. Aerobic exe rcise was not related \0 changesin B ~ I I (-0.33 BMI WMD, 95% CI-1.26 to 0.61) or bod)' mass (0.16bod)' mass WMD. 95% CI - 3.43 to3.76). RT was not rela ted to changes Inbody mass (-0 . 48 body mass WMD .95% CI -4.98 \0 4.0 2). Combmed aerobic and RT was not related \0 changesIn BMI (-0.78 BMI WMD . 95% CI - 1.89to 0.33) or body mass (- 1.02 bod)' massWMD , 95% CI - 2.85 to 0.82). However.waist CIrcumference did show improvement (- 3. 1 cm) after combined aerobicand RT (-3. 1 WMD, 95% CI - 10.3 to-1.2). This difference was significant.SBP. Aerobic exercise was related to adec rease to SBP of 6 mm Hg (- 6.08WMD , 95% CI -10.79 to - l .36). Thisdecrease was found to be statisllcallysigmficant, but there was sigmficantheterogeneu)' prescnt. RT was not related to a statisticall)' Significant changeIn SBP among patients with type 2 diabeles ( - 4.36 WMD, 95% CI -12 .14 to3.42). Combined aerobic and RT is related to a decrease in SB Por 3.59 mm Hg

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2-C hararlerislics of RT Irials

et al . 1998(Supplementary Ref. S22)

et a1.. 2002(Supplementary Ref S2l)

et aI., 2002(Supplementary Ref. 523)

et 31 , 2003(Supplementary Ref. 519)

et aI, 2007(Supplementary Ref S20)

et al . 2007 (24)

a],. 2009(Supplementary Ref. 524)

InteryenttonRT vs. no exercIse

control

RT vs, nontrammgcontrol

Moderate weIght loss +supervised high-mtenstt),RT \'5, moderate weigh tloss + control

Moderate mtenSll)' RT\"S, nontrammg control

RT \"S, nontrammgcontrol

RT vs, control

RT \'5. rouune care

Frequency. mtenslty, time, duratlonF 3 da)'s/ ....eekI: 50-55% of I RMT' 3 setS of 10-15 reps

(2 setS only for first 2weeks)D: 8 .....eeksF 3 dars/weekI 60-80% of 1 RM progressmg1070-80%

of mldslud), I R ~ l T 3 sets of S-IO repsD: 16 weeksF: 3 days/weekI: 50-60% of 1 RM progreSSing10 75-85% of 1 RM

T J sets of 8-10 reps0 : 6 monthsF' 3 days/week1 max wetght at whtch

subject could complete10 upper and 15 lowerbody selS; increased by5% when subjectcompleted prescnbedCIrcuits and repsT: 2 setS of 12 reps(I set onl)' for first week)

D 10 weeksF: 3 day"Sl\\letkL 60-80% of I RM for

8 weeks. then 70-80%of mldstudy I RMT' 3 setS of 8 reps0 : 16 weeksF: J days/weekI max weight at which"r can be doneT 2-3 setS of 7-9 reps0: 22 weeksF 5 day"Slweek + 2 supeT\'l.sedsessions lsI month then 1

supervised session each monthI: Increased len sion of bandwhen 12 reps performed wnhgood form

T' 2selsof 12 repso 16 weeksduration, F, frtqucncy. I. tnlensnr. reps. repcllllons. RM, rt:pcllllon Ilwumum, RPE . ra1lng of pcrctl\td tumon, T. umt

Chutlyh and Pelreila

AdherenceDIrectly supervised

Direc tly superVISed

DIrectly supervised

Duecdy supen'lSed

DIrectly supemsed

SupeT\llsed weekly for fiT5t 4weeks, biweekly thereafter;logs; Identificatlon scannmgal gym, HR monitors

DIary

- 3.59 WMD, 95% C1 -6.93 to -0.24).. O N C L U S I O N S ~ M a n a g e m e n t of CV

is a priority among individuals

with type 2 diabetes, because CVD is theleading cause of death among individuals\vith diabetes (8). Funhcnnore , IndIvidualswith type 2 diabetes are at an Increascd nskof microvascular complications. According

to the 2008 Canadian Diabetes Association guidelines, the main interventionsfor reducing risk of CVD include controlling blood glucose and blood lipid levels,as well as controlling BP (8). Therefore .

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Excrcisc and can/jowlsc lliar risllTable 3-Characlcr;Slics of C Q l I l i n c r l l l l ' o b j mid RT Irill'S

StudyTessle rc t al.. 2000(Supplememary Ref. S30)

MaJomna el aI. , 2002(Supplementary Ref. S29)

Cuff el al.. 2003 (22)

LOl!llaala et aI., 2003(Supplement:u)' Ref. 527)

Balducci et aI. , 2004(Supplememary Ref 525)

L01!llaala el aI., 2007(Supplementary Ref. 528)

Sigal et al.. 2007 (24)

ImeryemlOnMixed acroblc (rapid walkmg) ..

RT (2 sets of 20 reps ofmajor muscle groups)

(t rcull tr:unmg (7 RT +8 aerobic exercises)VS, cont rol

Combmed aerobiC (treadmill ,bicycle. recumbem stepper.clltpttcaltmmer, rowingmachme) .. PRT (5exercises of major musclegroups) \'5, control(usual C:lre)

Ci rCUli tralnmg (8 exe rcisesfor upper and lowerex tremllles) vs. no exercisecomrol

Aerobic cxerclse (ircadmlll,bicycle, or elhpllcal) ... RT(6 exercises for major mu sclegroups) \'s standardcare control

ExerCIse (Joggmg or walkmg ..RT) \'S , control

AerobIC exercise (t readtntll,bicycle ergomeler) +RT \s. comrol

1234 D IARETES U \'01 mil: 34, MAY 20 11

Frequency. intensity. lime, dur:l1IonF 3x /weekI. 35- 59% HR max progressmg

to 60-79% HR max at week 4unul the end of the stud)':2 sets of 20 reps

T 60 mm (20 aerobic. 20 RT)D: 16 weeksF' 3days/week[. 55 % pretrammg MVC to 65%

b)' week 4 (RT) : 70% peakbaselme HR - 85% b}' week6 {aerobic}

T60mmD: 8 weeksWork:rest 45: 15 sF: 3 da)'s/weekI. 60-75% HRR : 2 sets of 12 repsT' 75 min0: 16 weeks

F: 2 days/week[: 70-80% max \'olulltaryCOntraction for 10-12 reps:65-75% Val max

T: minimum 30 olIO altarge( HRD: 12 monthsF: 3 days/weekI 40-80% HR reser\'e (ae robic);J sets of 12 reps (RT) al

40-60% 1 RM (n.'tesledevery 3 weeks)T 30 mm aerobiC" 30 mtn RT

D. 12 monthsF 2 d ~ ' s / w e e k 1: 65-75% VO l maxT mUltnlUm 30 mill at targetHRor m t e n s u ~D: 12 monthsRT :F: 2 da )'s/week1: 70-80% 1 R1'> lT: Three selS of 10-12 repsD: 12 monthsF: 3 da)'s/wee k1. start al 60, work up to

75% max HRT start at 15 mtn. workup to 45 minD: 22 weeks

RT ;

AdherenceDirectl}, super... lsed

Directly supemsed

One super.lsedseSSion/week

Tw o (of four) supervisedsessions/week: exercisedillry : exemse HR andmtenSII}' cont rolled

Supervised weekly for first 'Iweeks, biweekly thereafter:logs, identifica llon scanningat gym: HR monnors

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CllUdyll (luci P e r n " ( 1 able 3-COIrtinu edtudy lnteryentlon Frequency. rntensHy. lime. durallon Adherence

F: 3 days/weekl ' max weight at whrch"1" can be done

T: 2-3 sets of 7-9 repsD: 22 weeksKrousel-Wood et aI. , 2008(Supplementary Rd. S26) Exercise tapes (combinedaerobic + PRT) vs . no

exercise cont rolF: goal of 5 days/weekI: 3-6 t.IETs while us ing tapeT: 10-. 20-. and JO-mrn tapesD: 3 months

Activit} logs

umbers et a1. . 2008 (28) Circuli training (combinedendurance + RT)F: 3 days/week Directly supen'isedI: 60-85%max HR ;

\'5 . control RT : started at 60%. Increased!O 85% 1 Rt.'l, 3 setS ofIO-IS reps

T: 60 minD: 3 monthsD. duranon. F. frequency, HRR . hean rale reserve, 1, intensity: max. ma!l:rmum, MET s, m(13bohc eqUIvalents: MVC . m : . ~ l m "oluntar}' COntrnClion. PRT.progreSSive reSISlance tr:umng: reps, repeUlions: RM , repelilion maximum: T. lllne

we selected our outcome measures in thisre\' iew on the basis of these modifiablerisk factors for CYO.For each 1% increase in the level ofHbA te , the relative risk of CVO increasesby 1.18% (27), whereas each 1%decreasein HbA 1c levels is associated with a 37%reduction in microvascular complicationsand a 14% reduction in myocardial infarctions (28). Further, lowering HbA1ein patients with t)'pe 2 diabetes decreasesthe absolute risk of de\'c\oping coronaryheart disease by 5-17% and all causemonality by 6-15% (29). Because the relationship between the risk of CVD anddeath from CY causes is Hnear (28), wecan extend our findings of the effects ofexercise on HbA lc levels to the associatedreductions in CVO risk. The 0.67% reduction in HbA lc levels associated withombined aerobic and RT is related to a26% decrease in risk of microvascularomplications and a 10% decrease inrate of myocardial infarctions. Similarl)"

the 0.6% decrease In HbA] c levels relatedto invoh"ement in aerobic exercise is asociated with a 22% decrease in microvasular complications risk and an 8%

reduclion in myocardial infarction rate.hese effects are comparable to that ofdrug monotherapy, which is related to a0.5-1.5% decrease in HbA \c, depending

on the pharmaceutical agent used and thebaseline HbA lc level of the individual(30). Because the extent of HbA lc reduction is positively related to the baselinevalue of HbA 1e, combined aerobic andare.diaoclcsjournals.org

strength training, as well as aerobic training. may be the preferred first-line treatment option for individuals with lowerbaseline HbA 1c values who want to delaythe onset of pharmaceutical treatment.Future studies should also consider theimpact of concomitant use of nonpha rmacologic and drug Iherap)'on CV causesof type 2 diabetes .According to the Canadian DiabetesAssociation, BP treatment targets for individuals with type 2 diabetes includemaintenance of SBP < 130 mmHg (8).Both aerobic and combined aerobic andRT exercise were related to statisticallysignificant declines in SBP (6 mmHg and3,59 mmHg, respewvely) . Moreover. themean SBP of the aerobic exercise trialsranged between 126 and \33 mmHg atlast follow-up (mean SSP eo 130 mmHg).whereas the mean SBP of the combmedaerobic and RT ranged between 129 and138 mmHg (mean SBP eo 134 mmHg) atlast follow-up. Therefore , aerobic andcombined aerobic and RT exercise havethe potential to have a clinically significant impact on the presence of hypertension among individuals with type 2diabetes. Both combined aerobic andRT, as well as aerobic exercise , were foundto decrease triglyceride levels by 0 .3mmoVL Howeve r, we did not find stat isuca! support for the existence of a relationship be tween aerobic or RT an dimproved HDL-C and LDL-C among indIviduals with type 2 diabetes. In a randomized controlled trial of the effeCls

of aerobic exercise on lipid levels inoverweight individuals with mild-tomoderate dyslipidemia. it was foundthat improvements in lipid levels weremore closely associated with exercisequantity than exercise intenSity o r improvements in fitness (3 1). Therefore,perhaps exercise imerventions preSCribing higher levels of exerc ise quantityneed to be carried out to positively affectlipid le\'e\s in individuals with type 2diabetes.

Ou r meta-analysis found lillIe suppan for the benefits of RT on 01 riskfactors in type 2 diabetes. The energyexpenditure of RT is affected by thenumber of setS and repetitions. reSI interval, number of repeti tions. velOCity ofmovement, and load involved in theworkout (32). Moreover, the energy expenditure of RT exercises al so depends onthe combinations of muscle groupsworked (e.g., exercises im'olving greatermuscle mass are associated with significantly larger energy expenditure) (33 ).Therefore, perhaps the RT intervemionsincluded in this analysis were not conducted at an intensity high enough to elicitmeaningful increases in energy expenditure. Bloomer (34) carried OUt a randomized cross-over toal invohing 10 healthymen to compare the energy expenditureand physiologic responses to moderateduration resistance versus aerobic exercise. They found that despi te beingmatched for total time and relative intensity. the energy cost of continuous aerobicD I,\BETE!i CARE, VOLUM[ 34. MA Y 2011 1235


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Exercise amI cardiOWlSc llla r risllexercise was greater than thm of intem,ittent resistance exercise (34). Therefore, future studies on the effect of RT in type 2diabetes should investigate the effects ofhigh- repe tit ion, high-set weight lifting,which is carried out at higher aerobic levels than the more tradi tional power-liftingapproach. When designing futu re aerobicexercise inte rventions, endu rance exercises should be prescribed in te rms ofVO l rese rve , not VO l max, because VO lreserve has been established as beingdirectly related to other relative (HRreserve, HR max, the Borg rat ing of Pe rceived Exertion 6-20 scale) and absolu te(me tabolic equivalents) classifications ofexe rcise intensity (35). Further. futurestudies could identify ind ividual metabolic targets, such as the maximal levelof lipid oxidation during exercise. Thisin tu m would allow future meta-analyststo more accurately compare the effects ofd ifferent intensity le\'els of exercise onou tcomes of interest.

Comb ined aerobic exercise and RT, aswell as aerobic exercise carried Out on itsown, laking place al least two times perweek m an intenSity of 60-85% of an individual's HR maximum, is related to statistically Significant declines in HbA Ic ,triglyceride levels, waist Circumfe rence,and SSP among individuals with type 2diabe tes: howeve r . these exe rcise approaches are not related to signirlcantchanges in weight or BM I. o r to statistically Significant changes in HDL-C andLDL-C levels. When RT is not combinedwith other fo rms of exercise, it is not significantly related to changes in HbA\c levels or to changes in SSP. More researchneeds to be conducted before the effectsof RT on HDL-C. LDL-c' and triglyceridele\'els can be discerned .Additional reference sources can befound in the Supplementary Data.

Acknowledgme nts-N o potent ial conflicts ofinterest relevant to this article were reported.t\.e. was im'oked 10 the construction andsearch stmtegy and contnbuted 10 \1'TLling IhemanuscnJX . RJ .P. was Im'olved in the conception and construction of the search strategy,adjudIcation of articles mcluded in the ana lysis.and writing and editing the manuscript.

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chudyk et al 2011 effects of exercise on cardiovascular risk factors in type 2 diabetes

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