οruncl sden,Fc paper

ずF5従ht市e⊂ardiology

QuadriCeps isometric strength asa predictor of exercise capacity incoronary artery disease patients

覇難嘔撃百響羅鄭IFiTakashi Masudai'5

lntroduction

Excrcisc capacity,as asscsscd by peak V02 0r CStimated

nlctabolic cquivalents(eⅣ IETs)、 iS known to bc all

illlportant prcdictor of physical disability and nlortality

in healthy individuals and patients v′ ith cardiovascular

discasc 12 For this rcason, inlprovclment in cxcrcisc

capacity is onc of thc main goals of cardiac rehabilita―

tion、 rcsulting in both a rcduction of rnortality l－ isk and

an increased lcvel of cvcryday habitual activities 3 4 Thc

rcduction of mortality risk for cach l― cⅣIET incl・ case i11

exercise capacity rangcs betwcen 10シ t and 2500 and is

evidcntin young and elderly subJccts of both sexcs with

AbstractBackground:Quad百 CepS strength is related to exercise capacity in normal sublectS and different pajent popula● ons,

but the relajonship between maximal quadttceps isometttc strength(QIS)and difFerent exercも e caPaCity levels in

coronary artery disease(CAD)pajentS has not been systemaucally evaluated yet

Method:We studied 621 Pajents(606± 9 9 years,538 males)wlth recent coronary artery byPass grafting or myo－

carditt infarcJon,who undettent treadmill exercise tesung,maximal QIS meaSurement(hand_held dynamometry),and

coronary artenography.Maximal QIS Was expressed as absolute value(kg),%bOdyWeight,and%predicted maximum.

Logistic regression was used to assess the relationship of maximal QiS,age,sex,nunnber of diseased coronary vesseis,

peak systolic blood Pressure,peak heart rate,brain natriuretic Peptide,and left ventricular eleCtiOn fraction with 5,7,

and 10 esumated metabolic equ～ Jents(eMEtts)eXercise caPaCity leveis

Results:Maximal QIS%bOdンn″eight was the strongest predicto「 of exercも e capacity in each eMETs categorメ Receive「

。Peraung charactensucs curves idenJned maximal QIS Of 46,51,and 59%bodンら″eight as the best predicJve cut offs for

5,7 and 10 eMEtts, respectively・ with positive predictive values of O.72,066,and 0 67,resPectivelメ

Conduslons:Ma×imal QIS iS related wlth eMEtts leveis reached at exercise tes● ng in CAD pajents,and iden● led

maximal QiS Cut_。 ff values for eMETs predictlon may be used to set strength training goals according to padents'needs

with regard to habitual Physical activity level Hand－ held dynamometry may meet the need of easiness of use and low cost

required for strength evaluation in large― scale ciinical trials

KeywordsCardiac rehabilitation,coronary artery disease,exercise capacity,muscle strength

Received 25 SePtember 2012;accePted 10 May 2013

EuroPean loorna1 0f Preventive

Cardio oy

O(00)1-7

◎ The EuroPean Society of

Cardiolo,2013

RePrいtS and Permisslons:

sagePub co uk4ournJSPermヽsbns nav

DOL 10 1177′ 2047487313492252

eiPC Sagepub com

OSAGE

IKtasato∪niversiγ Graduate School of vedical Sdences,Sagamihara,

laPan2Kitasato UniverJty HosPにal,Sagamihara,Japan3scientinc lnstitute of｀ /eruno,ヽ /eruno,ltaly4Ktasato Universty School of Medicine,Sagamihara,,aPan

SKにasato UnⅣerJり Sagarrihara,lapan

CorresPonding author:

Takashi Masuda,Department of Rehab∥itaJon,School of Allied HeaLh

Sciences, Kに asato Universitγ  l－ i5－ l Kitasato, M nami－ ku, Sagamihara,

Kanagawa,252-0373 1aPan

EmJI:● k9999@med ktasato－ u ac,P

Eurοpean JOυ rnd οfPrevenJve Ccrdolos  θ(θの

and without cardiovascular disease、 vith mortality risk

decrcasing、vith incrcasing cxercisc capacity and rcach―

ing an asymptotc at around 10 cヽ /1ETs 2

Bcsidcs acrobic exercisc, many rcports document

that strength training also ettectively improves exercise

capacity in individuals M/ith and without cardiovascular

discase 5 8 The bulk of evidence suggests that loss of

muscle strength is an important predictor of physical

disability9 and reduced exercise capacity in cardlac

patients ll 15ン 1。 reovcr,analo30usly to and indcpcnd－

cntly of exercise capacity, inuscle strength has bcen

shown to prcdict lllortality in both young and cldcrly

normal and in difFerellt patient populations.16 19

Hence, rcsistance training is currently accepted as a

main colllponent of comprehensive cardiac rehabilita―

tion, leading to illlprovements in quality of lifc and

raising the performance level for occupational and rcc―

reational activities 6.20

Sevcral papers have assessed the relationship betv/ccn

quadriceps strength and cxercisc capacity in normal sub―

jects and chronic heart failure patientsぅ ll.12.21 but Such

relationship has been addressed to date only in small

groups of patients with coronary artery disease(CAD)

with contradictory rcsults 9'13 1522 0urヽ Vorking hypoth―

esis was that a positive correlation M/ould exist bet、 veen

maximal quadriceps isomctric strength(QIS)and exer―

cisc capacity in CAD paticnts and that,if this、 vere true,

such a relationship would provide usefulinformation in

the clinical setting ror a strength training prescription

tallored on daily habitual activities in this population.

Thc purpose ofthc prcsent study、 vas thus to investigate

the relationship bctwcen ma対 mal QIS and cxcrcise cap―

acity and to identitt thC levcls of ma対 mal QIS corrcs―

ponding to those of given habitual activities in a large

cohort of patients with CAD

Mёthods

Study pOρ υbJOη

This study consldcrcd 772 consecutlve patlents agcd

30-80 years、 vith a recent aCute cardiac event, referred

to our institution for a cardiac rchabilitation pro－

grarnme'om l January 2005 to 30 December 2010.Patients' diagnosis was dcterlllined as fonoM/st a

recent coronary artery bypass grafting (CABG)replaced othcr possiblc adnlitting diagnoses, such as

unstable angina or lalyocardial infarction(MI)1 0n the

other hand,a rccent MI without subsequent CABGM/as coded a, MI irrespective of possible subscquent

percutaneous coronary interventions Exclusion criteria

were:(1)treadmill exercise testing stoppcd for reasons

other than muscular fatiguel(2)orthOpaedic, ncuro―

logical,and/or pulmOnary comorbidities limiting fllnc―

tional  capacityi  and  (3) cliniCal  instabilization

According to such criteria, 621 patients wcrc included

in the study Of thc 151 excluded patients,Hl(7300),

27(18%),and 15(9%)met the exclusion criteria l,2,

and 3, respectively The clinical characteristics of the

study populatiOn arc shown in Table l

´ゝll patients under、 vent an cchocardiography and a

selective coronary artcriography as a part of their rou－

tine clinical′ inStrumcntal cvaluation Coronary lcsions

M/cre considered hacmodynanlically signincant v/hen

they causcd a 75シ t rcduction of the corOnary lulalinal

diametcr(50%rcduction for the left main coronary

artery) The Study protocol conforms to thc cthical

guidelines of the 1975 Declaration of Helsinki, and

was approved by the Ethics Conlllllittee of Kitasato

University Hospital.  ハ、1l patients gavc their informed,

written conscnt to participation in the study

Treadr17′〃exercise testing

All patients undcr、 vent a symptolll― linlitcd treadlllin

exercise testing according to the Bruce protocol E(3G

Tab:e l. Patients'characteristics

Characteristic

Study PopulatiOn

(n=621)

SeX(male)

Age(years)

ハヽ/eight(kg)

Body mass index(kgjlm2)

Diagnosis

Myocardial infarction

Coronary artery byPass grafting

Time Jnce cardiac event(days)

Braln nat百ureic Pepjde(Pg/mり

Left ventricular electiOn fraction(%)

Medicajons

Angiotensin― converting― enzyme inhibitors

Angiotensin il receptor blockers

β―BIoCkers

MaximJ QIS(kg)

MaximJ Q:S(%bOdyweight)

MaximJ QIS(%Predたted maximum)

Exerdse caPacity(eMETs)

Peak heart rate(beats/min)

Peak heart rate(%PrediCted maximum)

Peak systolic blood PreSSure(mmHg)

Peak rate― pressure product(beats× mmHg)

Peak BOrg scale

538(87)

606± 99

636土 ￨18

236J=34

425(68)

196(32)

56■ 21

169± 281

48.l■ 10.6

254 (41)

310(50)

477(77)

34.6J= ￨ 1 4

54.4=土 154

938=L252

78± 15

138上 i9

87=上 12

169± 28

23,332± 5372

17.5土 ￨￨

Values are mean tt SD or● (%)eMETs,esimated metabdic equ市 Jent,

QIS,quadHcePs isOmetnc strength

Oownloaded fron cprsagepub com at OSAKA UNIV NINeEN KAGAKUBU on Seメ ember18,2013

Kσmiyc et c′

、vas continuously recorded  、vith an ergometric strcss

test systenl (ML－6500:  Fukuda Denshi, Tokyo,Japan), and b100d prcssurc  、vas nleasured every

ll■inute by the cuff method with an autOmatic rnanonl―

eter(FB－ 300: Fukuda Denshi) Rating of perceived

excrtion(6-20 Borg scale)was aSSCSSed eVery 3 minutcs

during the exercise phase and just before its interrup―

tion.Excrcise capacity M/as exprcsscd in cⅣ IETs,calcu－

lated according to the fo1lowing Bruce protocol― Specinc

equation accounting fOr handrail usc:23 cMETs=

(2587× TT+6004)′35,wherc TT is cxercise time in

lt1lnutes

A4σxima1 9υ adricepsた Omet″c strengゎ

measurennent

A few days after cxercise teslng,ma対 mal QIS Wasmcasurcd by a hand― held dynamometcr(μ  TaS MT-1,ANIⅣIA,Tokyo,」apan)Patients sat on a bcnch,and

the dynamomcter  、vas nxed to a rigid bar24 ThreC

5-second maxiinal isomctric voluntary contractions of

thc quadriceps wcrc conected for both legs, with thc

knee joint angle nxcd at 90°  of nexlon and hip joint

anglc sct at approxinlately 90° of nexion. rcspectivcly.

Right and left quadriccps、 verc tested consecutively./ヘ

rcst period of 30 scconds was prOvided bct、ハ/cen scts of

bilateral contractions Electrocardiographic data  、vere

continuously monitorcd via telemetry and blood pres－

sure v/as evaluated nlantlaHy bcforc and ilnmediately

after strength measurements Patients wcrc told not to

hold breathing during contractions to avoid thcValsalva manoeuvcr The highest right and left sidc

strength values v′ ere averaged and expressed as abso―

lute valuc(kg),relat市c to body wcight(%bOdywcight)、

and relative to age―  and scx― predicted valucs(ツ 6pre_

dicted maxirnum)based on available normative data 25

StaJsJcd analysた

Spcarman's rank correlation、√as calculated to evaluatc

the correlation between ma対 mal QIS Strcngth(abSO－

lute value,%bodyweight,and%predicted maximum)and cMETs Thc ma対 mal QIS parameter most corre―

lated to eⅣ【ETs M/as adopted in follo、ving analyses

Stepv/ise logistic rcgression  、vas used to cvaluate the

relationship bet、 veen exercise capacity categories of 5,

7,and 10cMETs and maximal QIS,agC,scx,number ofdiseased coronary vcssels, brain natriuretic peptide

levcl, lcft ventricular aCCtion ttaction,peak systolic

blood pressure, and hcart rate. The abovc― nlentioned

eNIIETs catcgories、 vere chosen as energctic costs cqual

to 5, 7,and 10  ⅣIETs and include, respectively, most

light― to－llloderate, moderatc― to― high, and high― to－ vig―

orous intensity houschold, occupational, and sports

activitics 26 1n furthcr analyses,we calculatcd the area

under the curvc(AUC)acquired fl・ om receivcr― operat―

ing characteristics(ROC)curVes to cvaluate the discri―

minating power of ma対 mal QIS in prcdiction of thc

thrcc cMETs categories Thc rclationship betv/een scn―

sitivity and spccincity of maximal QIS for prediction of

5,7,and 10 ch711ETs attainmcnt、 vas exanlincd by con－

structing scnsitivity and specincity Curves.26 An optimal

cut―ofF point inaxilnizing scnsitivity and specincity for

each eゝ/1ETs category、 vas dcterlllincd fronl the inter－

scction of thc scnsitivity and spccincity curvcs 27

All analyses、vere carried out v/ith the use of SPSS

for Windows 20 0 statistical package (SPSS  」apan,

Tokyo,Japan)The level of statistical signincance was

sct at a 2-tailcd′―valuc ofく(005

Resu!ts

C″nicσl charσ cteristics

The study population、 vas composed mainly by malcs

(´「 able l).About one― half of the patients had 273-vessel

CAD,with a left vcntricular systolic function on aver―

age at lo、vcr nornlal lilllits and a quite、 vell― prcserved

hacmodynalllic balance, as witncsscd by only slightly

elevatcd mean brain natriuretic peptide levelsi nlost

patients M/crc on angiOtensin― convcrting enzyme inhibi―

tOrS′ Sartanics and′or beta_blockers(Table l)

Maximal QIS COrresponded on average to around

one― half of body、 veight(even if With a large standard

dcviation)and was very close to prcdicted maximum

(Tabに 1).Mean exerdse capadty was>5eMETs,attest―

ing a good average exercise tolerancc ofthe study popu¨

lation.but also in this case v/ith a quite、 vide dispersion

of individual valucs around thc rllcan(Table l)Mcan

peak heart ratc cxprcsscd as a percentage of prcdicted

maxinlum and mcan pcak ratc― prcssure product werc

consistent v/ith signincant exercise― induced wholc body

and myocardial stress,rcspcctivcly(Table l)

Exercise capσ city predictOrs

Maximal QIS Was signincandy related to cMETs

(″ =0.42 for absolute valuc,r=0 43 for%bodywcightvaluc,and′・=0 29 forシ 6predicted maximum value,all

″く0001)By deSign, maximal QIS CXpresscd asシ6bodyM/eight、 vas used in follo、 ハ/ing analyses.At step―

wise logistic regression,ma対 mal QIS and peak hcart

rate、verc the only independent prcdictors of a 5 eMETs

exercisc capacity attainmcnt(Table 2).On thC Other

hand,the predictive nlodcls of 7 and 10 eNIIETs attain―

ment included several other indepcndcnt prcdictors of

cxcrcise capacity in additiOn to maximal QIS and peak

heart rate(Tablc 2)Of notC,maximal QIS waS One Of

thc strongcst independent prcdictor in all eMETs pre―

dictive models(TablC 2)

Oo″nloaded from cprsagepub cOm at OSAKA UNIV NINCEN KACAKUBU on September18,2013

European」οurna1 0F Preventル e Cardbbgy O(001

Valdity ofmσ χirnd QIS cS an exercた e cσpadty

predctor

The AUC acquired flom ROC curves for maximal

QIS aS a predictor of a 5,7,and 10 eMETs cxercisecapacity attainment was 0 784(95%C10715-0854),0719(95% C1 0672-0767), and 0 720(95% CI0634-0806),respectively(all′ <0.001)The sensitiv―

ity and specincity curves for maximal QIS aS a pre―

dictor of each cゝ/1ETs levcl attainnlent arc sho、 vn in

Figure l Maxittal QIS Of 46,51,and 59° 。body―

weight were identined as optimal cut― ofF points max―

illli2ing sensitivity and spccincity fOr prediction of 5,7,

and 10eヽ/1ETs cxercise capacity attainment, respect―

ivcly,  、vith positive prcdictive valucs of 0 72, 0.66、

and 0 67, respectively.

Discusslon

The main inding ofthis study was that maximal QIS iS

signiflcantly related to exercisc capacity in patients v/ith

CAI):as a consequcncc,cxCrCiSe capacity,as cxpresscd

in eヽ/1ETs categories, can be predicted according to

maximal QIS mCasurcment in this population.Overall, thcse results can help clinicians to sct the

goal of strcngth training progranlmes in C´ 、lD paticnts

according to patients'needs about household,occupa―

tional, and sports activity level and to ascertain

patients' exercise capacity when excrcise testing is not

available or fcasible

Tab:e 2. Logistic regression modeis for different eMETs ievels

Maximal QIS σnd exercな e capadty h CAD patients

lt is、vell knoM/n that exercise capacity is rclated to age,

physical activity level, and cardiovascular clinical

status. Additionally, many reports rcfer to muscle

nlass or strength as a factor linked to cxcrciSe capacity

both in hcalthy suttectS'and paticnts with chronic

heart failurc.810112111。 、vcvcr,the rclationship bctwcen

muscle strength and cxercise capacity in C´ IゝD paticnts

has becn cvaluatcd only in sman patient groups,、ハ/ith

contradictory results 9｀13 1522 The prescnt study is the

nrst o syStenlatically cxanlinc thc association betv/ccn

maximal QIS and exercise capacity in a largc cohort of

CAD patients Our results show that maximal QIS Was

among thc strongest independent predictors of each

cxcrcise capacity catcgory a■ er attusting fOr sevcral

confounding Factors Of notc. the logistic regression

lllodcl for thc 5 eⅣIETs catcgory includcd only inaxinlal

QIS and heart rate,whereas the 7 and 10eMETs excr－cise capacity levels  、verc indepcndently predicted also

by sevcral othcr parameters These nndings iend sup―

port to the hypothcsis that, in morc unnt pcople(ie

older and′ or diSCased)、 excrcise capacity may bc limited

not only by central cardiovascular factors,but also by

leg strength itself 5

Clinicσ l implicaゴOns oFmaχi“ σl QIS Cut οfFS in cAD

patients

Strength training is M/idcly acceptcd as a prinlary conl―

ponent of comprehensive exercise programnles of

eMET level B tt SE Odds rajo(95%Cl)

5 eMETs

MaximJ Q!S(%bOdywdght)

Peak heart rate

7 eMETs

MaximJ QIS(%bOdyweight)

Peak heart rate

Peak systolic blood Pressure

Male sex

Age

い/EF

10 eMEtts

MaximJ QIS(%bodyweight)

Peak heart rate

Peak systolic blood Pressure

Age

Male sex

0082± 0017

0060■ 0010

0.046■ 0.009

0044圭 0006

00141L0004

0908=上 0300

-0035± 0.013

0025=上 0011

0030■ 0008

0.025=L0008

0.011二 LO.004

-0029■ 0.013

0,45=LO.548

<0001

<0001

<0001

<0001

0001

0002

0009

0.019

<0001

0002

0.O15

0.028

0084

1086(105∝ I.122)

1062(1041-1084)

1047(1029-1066)

1045(1032-1059)

1014(1006-1023)

2480(1 378-4.463)

0966(0.941→ 991)

1026(100牛 1048)

￨.030(1013-1048)

1025(1.00%l・041)

1011(!00ル 1020)

0971(0947■ 997)

2573(088←7529)

eMETs,esJmated metabolic equivJents LVEE left Ventncular elecJOn fracion:QIS,quadrlcePs iSOmetnc strength

SE,standard error;Cl,conndence interval

Kσmiyθ et al

cardiac rehabilitation  Hcncc, the idcntincation of

strcngth values corrcsponding to specinc exercise cap―

acity levcls and leisure－ tilnc and occupational activities

may be useful to propcrly dcane the goals of strength

training protocolS ThC rcsults of thc prcscnt study

show that a ma対 mal QIS of arOund 45,50、 and 60

シ6bodyv/eight is nccded to achieve excrcisc capacities

Of 5,7,and 10cMETs,respectivcly As givcn eMETslcvels can be linkcd tO a broad range oF specinc house_

hold, occupational, and sports activities,26 thcsc nnd―

ings underlie thc possiblc correspondence beい ハ/ccn

maximal QIS and habitual acivity levels in CADpaticnts(Table 3)This hOldS truc cspccially br the

5 eNIETs category, in which the highest positivc

5 eMETs l。。

も 080

3 060

を 040

8  020

000

7 eMETs００

０ ８０

０ ６０

０ ４０

０ ２。

０ ０。

ゝ〓０嘔Ｏ００の

ＯＣｏ

＞〓＞このＣＯ∽

Ｓ柳　　０８０　　０６０　　０４０　　０２。　　ｍ

ＥＴ

　

　

ゝち一も０３

０Ｅ

´Σ嬌ｃｏの

Ｍ

0   10  20  30 40  50  60  70  80  90  100

Max ma QIS

10  20  30  40  50  60  70  80  00  100

Maxima1 0 S

￨           －ヽ

, ~－~~~~~~－

￨

￨

0   10  20  30  40  50  60  70  80  00  100Max ma Qls

Figure l. Sensitivity and specificity curves for maximal quadri―

CePS iSOmet● c strength(%bodyWeight)as a Predictor of eMET

attainment

eMETs,esjmated metabolic equivalents QiS,quadncePs isomet―

ric strength

prcdictiVe valuc was observed For examplc, a max―

imal QIS Of 45 00bodyweight would be nccessary ior

paticnts to perform most light－ to― ntOderate intensity

activiticsi a maximal QIS Of 50%bodywcight to pcr－

form most modcrate― to―high intensity activitics;and a

ma対mal QIS of 60%bodyweight to pcrform mosthigh― to― vigorous intensity tasks (Table 3). In thC

light of the above, thc maximal QIS cut¨ OfF values

identincd in this study may be used in CAID patients

as targets of strcngth training progralnllles,according

to individllal needs about housch。 ld, occupational,

and sports activity levels.  レIoreovcr, thc possibility

to indircctly evaluate by ma対 mal QIS measuremcnt

the eNIETs lcvcl attainablc at excrcisc tcsting could

bc useful to evaluate thc exercisc capacity of patients

v/ho cannot undergo formal exercisc tcsting becausc of

clinical conditions and to those scttings that do not

havc excrcise tcsting cquipnlcnt available  lt ntust

be ackno、 ハ/1edgcd, however, that isometric strength

evaluation does not account for safcty aspects that

would be identined if a symptonl-lilllitcd exercise

test vvith E(〕 (3 and  blood pressure l12onitoring

、ハ/as conductcd

QIS measurernent by hanひheld d/η σmorneter

VVe uscd a hand－ hcld dynamollleter to nlcasure nlax―

imal QIS Such dynamometer is widely uscd in clinical

practicc or conllllunity medicinc because of its silnpli－

city,objectivity,and responsiveness in llleasuring quad―

ICTぶ黒L品

:胤l露=鰐

吼選Ittt譜nlometers providc accurate asscssmCntS of dynamic

and static inuscle strength and are usually the prcferred

option for clinical studies Ho、 vever,thё ir use in large―

scale epidemlological studies is limited,bccause tle

equipmcnt is costly and not portablc,and,as a consc―

qucnce,  muscle  strength  measurenlent  is  often

olllittcd 29′ sヽ the normative values for hand－ hcld dyna―

momctry and its tcst― retest reliability in measurcment

of thc isomctric musclc strength have already been

established in healthy persons,25 the CXpccted values

of lnuscle strength obtained in the present study can

be universally applied in many kinds of hospital and

home rchabilitation settings

Study″ rnたa百ons

The use of an indirect descriptOr of aerObic powcr

(cMETs)for CXercise capacity asscssment may bequestionable, since aerobic pov/cr can be overesti―

matcd M/hcn indirectly asscsscd using the Bruce proto－

coll especially in patient populations 30 H。、vever, thc

equation for peak NIETs estiination used in the cur―

rcnt paper has bccn sho、vn to provide the lowcst

Eurο pecn OfPreVenJve Cardlology  θ(0の

Table 3. Association of quadricePs isonnetric strength with leveis of exercise caPacity and habitual activities

QiS(%bodPVeightl eMETs Hab;tual activity intensity Habitual activity type

Cleaning,kitchen activity.laundrメ machine

tooling,electrical work

Digging,carrying/choPPing wOOd,mowing iawn,

liたing tems conunuousヶ (45-9 kg),WJttngon iob(55km/h)Carrying oblects≦ ll kg

Tennis single,golf without cart,bicychng

(19-22 km/h),using heavy tools,walking ca■

rying oblectS(23-34 kg)

Habitual activity tyPes reported ior each quadricePsisometric strength category are notintended to be exhaustive Ainsworth et a1 26 giveS a comPlete

llst of acJvlties associated wth the different QiS/eMETs categones eMETs,esimated metabolic equivalents

Light to moderate

Moderate to high

High to vigorous

discrepancy bctヽ/een estilllated and actual NIETs,、 vith

a nlcan valuc of 0 51 NIETs in paticnts  、vith signs

and symptoms suggcstivc for myocardial ischellnia 23

Such a value cquals a mcan dimerence of around18ml′ kg′min bCtWecn the estimated mean pcak V02

of 27 3 mlノ kg/min in the study population(Calculated

as 7.8cMETs× 35 ml′ kg≠min)and the actual peakrヽ02, ic  a 6シ6 discrepancy,  、ム/hich seems indecd

acceptable Also thc exclusion from the study ofpaticnts  、vho stoppcd exercise testing for reasons

other than muscular fatiguc may be questioned, as

this group docs include patients in、vhonl a peak exer―

cise capacity evaluation with tools di∬ erent by cxcrcise

testing vノ Ould be most indicatcd However, the inclu―

sion in the study of paticnts likely not attaining'truc'

maximal e∬ort, M′ ould havc signincantly confounded

the intcrpretation of the maximal QIS VS eMETsrelationship

Conclυ sions

The rcsults ofthis study demonstratc that ma対 mal QIS

is related to excrcisc capacity in paticnts v/ith CAD and

that ma対 mal QIS values Of 45,50,and 60%body－weight can be used to predict excrcisc capacity levcls

of 5,7,and 10cMETs,respectively Thcse nndings can

be used in cardiac rehabilitation for the dennition of

strcngth training goals according to patients' nceds

about dally activity lcvcl, and to indircctly evaluatc

exercisc capacity、 vhen exercise testing is nOt available

Finally,the rcsults ofthis study lend support to the usc

of hand－held dynamomctryお r maximal QIS measure―

mcnt in large－ scale clinical trials in CAD patients

Funding

This study was supportcd in part by the Ministry ofEducation,Scicnce and Culturc in Japan(n。  15500383)

Conflict of interest

Thc authors deciarc that therc is no conflict of intCrCSt

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