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Incidence of VO2Plateau at VO2max

INT-O*./TION

Ma'i)al o'*+en u(ta?e 1"O7)a'3 is the &unda)ental )easure o& e'ercise (h*siolo+*, and in co)ination -iththe conce(t o& a "O7(lateau, has een descried as the single mostinfluential concept in modern exercisephysiologyH 153. "O7)a' is -idel* reco+nied as oth a re(resentation o& the &unctional li)itations o& the

cardioascular s*ste) as -ell as a )easure o& aeroic &itness. This )easure ori+inates &ro) (ioneerin+ research

* A. ". !ill and collea+ues 173 that not onl* introduced the conce(t ut also atte)(ted to e'(lain its

(h*siolo+ical )echanis)s. !ill co))ented In runningthe oxygen intake may attain its maximum andremain constant merely because it cannot go any higher owing to the limitations of thecirculatory and

respiratory system.H !ill also atte)(ted to e'(lain the onset o& &ati+ue4 Atthe higher speeds therequirement of the body for oxygencannot be satisfiedlactic acid accumulates a continuously increasing

oxygen debt being incurred fatigue and exhaustion setting in.H These conclusions -ere acce(ted * e'ercise

(h*siolo+ists &or the ne't >8 *ears, and until recentl* the conce(t o& "O7)a'-as not criticall* ealuated *research.

Also introduced * !ill and collea+ues in the 5=78s -as the conce(t o& the o'*+en (lateau, or a )aintenance in

o'*+en u(ta?e -ith an increasin+ o'*+en de)and. This theor* -as su((orted * research &ro) Ta*lor et al. 103

that reealed a )aintenance o& o'*+en consu)(tion 1"O75@8 ))in3 -ith an increase in tread)ill +rade in

58< o& 55@ su9ects -ho co)(leted a discontinuous "O7)a'(rotocol. Neertheless, &indin+s * M*ers et al.123 de)onstrated that onl* t-o o& si' su9ects reealed a (lateau in "O7 at ter)ination o& ra)( tread)ill testin+.

These &indin+s re&utin+ the O7(lateau (heno)enon -ere corroorated * data in a &ollo-6u( stud* * theseinesti+ators 1@3, -ho then reco))ended the use o& a lon+er sa)(lin+ interal 108 6 ;8 s3 to enhance the

(recision o& +as e'chan+e data.

Recentl*, heated deate concernin+ the conce(t o& "O7)a'and the O7(lateau has led to a re6e'a)ination o& the

assu)(tions and &indin+s o& classic research * !ill and u(ton. Initiall*, !o-le*, Bassett, and Calsh 1;3

reie-ed the histor* and alidit* o& current criteria &or the attain)ent o& "O7)a'. The* concluded that none o&the estalished criteria -as suitale &or con&ir)in+ the a((earance o& "O7)a'. More recentl*, these researchers

1>3 res(onded to assertions * Noa?es 17.8;.; c), >8. ?+, and 0,757;@7 ))in, res(ectiel*.

All su9ects si+ned a -ritten in&or)ed consent e&ore olunteerin+ &or the stud*, and all (rocedures -ere

2

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a((roed * the uniersit* !u)an Su9ects Institutional Reie- Board. All su9ects resided and -ere

accli)atied to altitudes et-een 5,@7@ and 7,77@ ) aoe sea leel and all testin+ -as co)(leted at 5,@7@ )aoe sea leel 1PB: ;7; 6 ;0< )) !+3.

Ex3erimental Proceures

Each su9ect co)(leted three di&&erent "O7)a'(rotocols, a >@ Catt0 )in ste( (rotocol 1S3, a 7@ Catt)in

ra)( (rotocol -ith -or?load set at @8 Catt &or the &irst t-o )inutes 1R3, and the identical ra)( (rotocol underh*(o'ic 1FIO7:5@ O7, PB: ;0@ )) !+3 conditions 1!3. The order o& these tests -as rando)ied accordin+

to a atin S/uares desi+n 1=3 and assi+ned to su9ects ased on su9ect nu)er. Su9ects and all researchers-ith the e'ce(tion o& those o(eratin+ the +as e'chan+e s*ste) -ere linded as to the s(eci&ic "O7)a'test to e

ad)inistered that da*. All tests -ere se(arated * at least t-o da*s.

Initiall*, su9ects -ere &a)iliaried -ith the e'(eri)ental a((aratus, -hich consisted o& e'ercise on a c*cle

er+o)eter 1%oral ode , Gonin+en, The Netherlands3 durin+ -hich +as e'chan+e -as continuousl*

)onitored * a reath6*6reath s*ste) 1MedGra(hics %PL6D, St. Paul, MN3. !u)idi&ied ins(ired air -as

directed &ro) the hi+h6(ressure tan? throu+h a sa)(le o& distilled -ater, and then collected in a 588 Tissots(iro)etric tan?. Su9ects ins(ired air &ro) the tan? and e'(ired throu+h a (lastic )outh(iece and 06-a* ale

1!ans Rudol(h Inc., #ansas %it*, MO3. This )etaolic cart )easures e'(ired air&lo- * )eans o& a(neu)otach connected to the )outh(iece. A sa)(le line is connected to the (neu)otach &ro) -hich air iscontinuousl* (u)(ed to O7 and %O7 +as anal*ers. Prior to testin+, the (neu)otach -as calirated -ith ten

sa)(les &ro) a 0 caliration s*rin+e. The +as anal*ers -ere also calirated e&ore each test to roo) air and

)edicall*6certi&ied caliration +ases 157.7= O7 and @.57 %O7, res(ectiel*3. !eart rate 1!R3 -ascontinuousl* recorded durin+ e'ercise * electrocardio+ra(h* 1uinton Instru)ents, Seattle, CA3.

Prior to e'ercise, the su9ectKs hei+ht and -ei+ht -ere recorded. Seat and ar hei+ht o& the c*cle er+o)eter-ere set accordin+ to the su9ectKs s(eci&ications, and restin+ +as e'chan+e data -ere otained. E'ercise -as

then started, -ith su9ects co)(letin+ the (redeter)ined "O7)a'(rotocol o& et-een < and 57 )inutes

duration. Su9ects -ere instructed to )aintain a (edal cadence et-een

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-ES.4TS

5as exchange an heart rate ata

"O7)a'-as si+ni&icantl* di&&erent across (rotocols, F 17, 083:, ( 8.885, MSe:7@,;5>.;@. Aera+e

"O7)a'&or the ! 17,@07@;7 ))in3 -as si+ni&icantl* lo-er 1!SD:52.@7, (8.885, and !SD:5>.85,

(8.8853 co)(ared to the S 10,557;;8 ))in3 and R 10,757;@7 ))in3 (rotocols 1Fi+ure 5a3. A

si+ni&icant )ain e&&ect &or )a'i)al RER -as e'hiited et-een (rotocols, F 17, 083:0.>>, ( 8.8@, MSe:7.;8L 5860. !o-eer, Tu?e*Ks (ost hoc test reealed no di&&erences et-een )ean alues o& )a'i)al RER &or the R

15.08.53 co)(ared to the ! 15.28.53 or S 15.08.53 (rotocol 1Fi+ure 53. Ma'i)al !R -as si+ni&icantl*

di&&erent et-een the (rotocols, F 17, 083:57.7;, ( .8@, MSe:7

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*

Step Hypoxic

Protocol

1.0

1.1

1.2

1.3

1.4

1.5 b

Ramp Step HypoxicProtocol

RER

100

150

200 c

Ramp Step Hypoxic

#

Protocol

HR(b/min)

O7

Incience of a 3lateau in $OAll su9ects &or all tests de)onstrated a (lateau in "O7-hen "O7-as sa)(led either reath6*6reath or eer*

5@ s 1Fi+ures 7a and 73. Su9ects e'(ressed a (lateau @> o& the ti)e 17> o& 2< tests3 -hen data -eresa)(led eer* 08 s 1Fi+ure 7c3. For the 08 s sa)(lin+ interal, the R (rotocol dis(la*ed a (lateau in "O7

durin+ < o& 5; "O7)a' tests, -hile the S and ! (rotocols reealed a((earance o& the (lateau in ; and 50 out o&

5; tests, res(ectiel*. In contrast, onl* < o& su9ects 12 o& 2< tests3 dis(la*ed a (lateau in "O7-hen data -ere

sa)(led eer* )inute 1Fi+ure 7d3. Tale 5 (resents data o& "O7et-een "O7)a' and the closest nei+horin+

data (oint &or all su9ects across all (rotocols. It is eident that the "O7 at "O7)a' is s)aller -ith shorter

sa)(lin+ interals, and -hen +as e'chan+e data are otained reath6*6reath or eer* 5@ s, all su9ects dis(la*

5

+igure 14 MeanSD data &ro) the di&&erent (rotocols &or

"O7)a', 3 RER)a' and c3 !R)a'. : si+ni&icantl* lo-er in ! co)(ared to S and R (rotoco

Q : si+ni&icantl* lo-er in ! co)(ared to S (rotocol.

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a "O7at "O7)a'less than @8 ))in, indicatin+ a (lateau in "O7. Data o& the )ean chan+e in "O7et-een

"O7)a' and the closest nei+horin+ data (oint ased on ;8 s, 08 s, 5@ s, and reath6*6reath data reealed that

ariailit* -as +reatest &or the lon+er ti)e aera+ed data 1Fi+ure 03. This res(onse -as si)ilar &or each

(rotocol. Means o& this data &or the ;8 s, 08 s, 5@ s, and reath6*6reath aera+in+ -ere 52=.0>8., 77.05@.@, and 55.755.@ ))in, res(ectiel*. Cith the e'ce(tion o& the ! (rotocol, the )ean

"O7 at "O7)a'-as +reater than @8 ))in -hen lon+er 108 s and ;8 s3 sa)(lin+ interals -ere used.

0 2.5 5.0 7.5 10.0 12.5 15.0

Time (min)

0.0 2.5 5.0 7.5 10.0 12.5 15.0

0

1000

2000

3000

4000 b

Time (min)

VO2(mlmin)

0.0 2.5 5.0 7.5 10.0 12.5 15.00

1000

2000

3000

4000

Time (min)

VO2(ml/min)

c

0.0 2.5 5.0 7.5 10.0 12.5 15.00

1000

2000

3000

4000 d

Time (min)

VO2(ml/min)

+igure 4 A((earance o& the "O7 Plateau &or a3 55 reath aera+e, 3 5@ s ti)e6aera+in+ c3 08 s ti)e6

aera+in+, and d3 ;8 s ti)e6aera+in+ &or a re(resentatie su9ect.

Ta&le 16 $Oat $Omaxaxfor all Su&2ects across all Protocols an *ata Sam3ling Inter7als

!amp "tep #ypoxia

Subject 6a 5@ s 08 s ;8 s 6 5@ s 08 s ;8 s 6 5@ s 08 s ;8 s

1 >.7 07.8 >8.@ 7;;.8 75.5 5

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6 78.0 7;.8 08.8 5;5.8 07.> 02.8 00.8 5.8 5>.@ 572.8

7 2.8 77.8 78.@ 755.0 5.@ 25.8 [email protected] 58.; 05.8 7;.8 5;8.@8 57.5 =.8 @2.@ 752.@ 7>.8 5>.8 .@ 7.0 [email protected] 28.8 758.@ 22.; 55.8 0=.@ [email protected] ;.< 78.8 ;;.8 522.8.@ =0.> 8.;0 2;.8 2>.8 5@.< 7.> 0=.8 5>.8 08.813 @.8 ;.8 02.8 5=5.< 7.< 7=.8 >0.8 [email protected] 0.@ 5>.8 0>.8 =>..0 5;.0 .@

16 0.@ 8.8 7;.8 @2.< 2.8 75.> 0.8

a: "O7 in ))in: Breath6*6reath sa)(lin+ interal

BB 15 30 600

50

100

150

200

Ramp

Step

Hypoxia

Sampling Interval ()

V

O

2

(m

!/m

in)

+igure %4 The chan+e in "O7et-een "O7)a' and the closest nei+horin+ "O7data (oint &or each trial anddata aera+in+ )ethod. %o)(iled )eans &or all (rotocols at each aera+in+ interal -ere all si+ni&icantl*

1(8.8@3 di&&erent &ro) each other.

Attainment of -E- an heart rate criteria

Tale 7 de)onstrates that all su9ects e'(ressed an RER +reater than 5.5@ durin+ the R (rotocol. In contrast,

onl* 0< o& su9ects )et the !R criteria durin+ the R (rotocol 1their osered !R)a' at "O7)a' -as -ithin58 )in o& the a+e6(redicted theoretical alue 1778 a+e33.

Ta&le 6 Incience of the Attainment of - an -E- criteria at $Omax for each su&2ect,

Subject aTH HRmax(b/min)

bOBS HRmax(b/min)

nci!ence cR"Rmax nci!ence

1 5=5 5> No 5.0< es

3 5 es

5 5== 5

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6 5> es 5.0> es

7 5== 5 es 5.05 es

14 5=2 5= No 5.72 es

16 5=8 5>5 No 5.75 es

8S* 5 588

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a: Theoretical !R)a' : 1778 a+e3 : Osered !R)a' c: RER)a' criteria 5.5

*IS/.SSION

The (ri)ar* ai) o& the (resent inesti+ation -as to etter clari&* the "O7res(onse to e'ercise to "O7)a' usin+

)ore accurate sa)(lin+ techni/ues as -ell as a ariet* o& "O7)a'(rotocols and sa)(lin+ interals. The

)ost si+ni&icant &indin+ -as that a (lateau in "O7occurs uniersall* in *oun+, health*, actie su9ectse'ercisin+ to olitional &ati+ue -hen shorter sa)(lin+ interals 1reath6*6reath and 5@ s3 are used.

Second, the incidence o& the O7(lateau is inde(endent o& the s(eci&ic "O7)a' (rotocol (rescried. Theseconclusions )a* in&luence current e'ercise (h*siolo+ists to realie that the O7(lateau is a real

(heno)enon, and that its incidence is in&luenced * the s(eci&ic sa)(lin+ interal used * +as e'chan+e

ac/uisition s*ste)s.

The O7(lateau conce(t -as introduced * !ill and u(ton 173 in res(onse to an osered )aintenance o& "O7

-ith +reater s(eeds o& runnin+ in )en. Data otained three decades later * Ta*lor et al. 103 su((orted the

(lateau (heno)enon, as it de)onstrated a (lateau in "O7in 58< out o& 55@ su9ects co)(letin+ adiscontinuous "O7)a' (rotocol on a tread)ill. Further)ore, results &ro) Mitchell et al. 1583 reealed a

(lateau in "O7at "O7)a', re(resentin+ an increase in "O7@2 ))in at the hi+hest -or?load, in >7 o&su9ects co)(letin+ consecutie ut inter)ittent e'ercise outs o& 7.@ )in duration. Neertheless,suse/uent research 155, 573 in children re/uired to co)(lete tread)ill e'ercise to e'haustion su++ested

that a (lateau in "O71 7.5 )?+)in3 is elusie in this (o(ulation. Si)ilar &indin+s -ere re(orted *

Ro-land 1503 in nine children 1)ean a+e:55.25.7 *r3 and * Ar)stron+ et al. 1523 in 0@ children 1)ean

a+e:=.=8.2 *r3. More recent data (ertainin+ to the incidence o& a (lateau in "O7at "O7)a' is also

e/uiocal in adults. Sta)&ord 15@3 denoted a (lateau in "O71 5@8 ))in3 et-een successie tread)ill

+rades in ten )en co)(letin+ &our di&&erent "O7)a' (rotocols on a tread)ill. Further)ore, Eldrid+e et al.

15;3 osered a (lateau in "O710 )?+)in durin+ the &inal =8 s o& e'ercise3 in >> o& nor)al su9ectsand (atients -ith coronar* arter* disease co)(letin+ )a'i)al e'ercise. In addition, other researchers 15>3

re(orted a (lateau in "O71chan+e in "O75@8 ))in, or 7.5 )?+)in, et-een successie tread)ill

eleations3 in @8 and ;8 o& actie )ales co)(letin+ continuous and discontinuous "O7)a' tests on atread)ill. Si)ilar &indin+s re+ardin+ the (realence o& a (lateau in "O7in adults hae also eende)onstrated * other inesti+ators 15

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An initial e'(lanation &or the uniersal incidence o& the O7(lateau in the (resent inesti+ation co)(ared to

(reious &indin+s is the sa)(lin+ techni/ue used. Breath6*6reath +as e'chan+e o&&ers +reat te)(oralresolution * calculatin+ alues &or "O7and "%O7)ore &re/uentl* than (reiousl* estalished sa)(lin+

techni/ues. The 556reath )oin+ aera+e e)(lo*ed herein attenuated the )a9orit* o& inherent noise in

reath6*6reath data, as each reath re(resented the aera+e alue o& the &ie reaths &ollo-in+ and

(recedin+ it. Thus, a er* (recise re(resentation o& the "O76O7de)and relationshi( -as otained

throu+hout e'ercise, leadin+ to the ailit* to detect a "O7(lateau at "O7)a' i& indeed it did occur.Further)ore, the lon+er sa)(lin+ interals (ro(osed * (reious research 1@, ;3 -ould re/uire su9ects to

sustain -or?loads at or aoe "O7)a' &or u( to 7 6 0 )in to de)onstrate a (lateau, -hich is not &easile in)ost indiiduals. Also, oserations in our laorator* reeal that lon+er sa)(lin+ interals tend to

si+ni&icantl* underesti)ate "O7)a'. In the (resent stud*, the O7(lateau -as not al-a*s realied -hen +as

e'chan+e data -ere sa)(led eer* 08 s 1@> incidence3 and ;8 s 1< incidence3. $sin+ 5 )in dataaera+in+ techni/ues, Duncan et al. 15>3 osered non6incidence o& the (lateau in 2@ o& su9ects. This is

not sur(risin+, since such lon+ sa)(lin+ interals could easil* )iss the a((earance o& a (lateau in "O7.

Si)ilarl*, M*ers et al. 1@3 denoted a lac? o& a (lateau in "O7in ;; o& su9ects -hen +as e'chan+e -as

otained eer* 08 s. There&ore, it is a((arent that the duration o& the s(eci&ic sa)(lin+ interal used has adra)atic e&&ect on (realence o& the "O7(lateau.

The rather strin+ent (lateau criterion 1"O7@8 ))in -ith an increase in (o-er out(ut3 used in the (resent

stud* lends &urther credence to our &indin+s. In &act, it has een su++ested that cut6o&& alues o& @8 6 ;8))in constitute a true (lateau as the* a((roach the li)itations o& oneKs ailit* to )easure chan+es in

"O7)a' 1;3. The criterion used * Ta*lor et al. 103, a chan+e in "O75@8 ))in or 7.5 )?+)in -ith

a 7.@ increase in +rade, has een e'tensiel* used to con&ir) incidence o& "O7)a'. Astrand 1783e)(lo*ed a )ere leelin+ o&& o& o'*+en u(ta?e as a suitale criterion, *et in earlier -or? 153 are characteried * 5 )in sa)(lin+ interals -hich -e sho- are unale to (recisel* identi&* a

(lateau in "O7. A+ain, it is a((arent that the s(eci&ic sa)(lin+ interals used +reatl* in&luence the

(realence o& the O7(lateau across di&&erent "O7)a' (rotocols.

10

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Des(ite the &act that the conce(t o& "O7)a' has e'isted &or oer >@ *ears, currentl* no suitale criteria e'ist to

con&ir) its incidence. A thorou+h reie- 1;3 o& the e&&icac* o& a (lateau in "O7, eleated RER and loodlactate concentrations, and )a'i)al heart rate hi+hli+hted the li)itations o& (reious do+)a, na)el* that

)an* o& these criteria -ere deelo(ed &ro) inter)ittent (rotocols -ith dra)atic increases in (o-er out(ut

(er da*. In contrast, at the (resent ti)e continuous tests -ith s)aller -or? rate incre)ents (er sta+e are

-idel* used. Findin+s &ro) the (resent inesti+ation o&&er t-o suitale criteria to con&ir) the incidence o&

"O7)a'4 153 a (lateau in "O7 @8 ))in -ith an increase in (o-er out(ut, and 173 RER at "O7)a' 5.5@. The )a'i)al !R criterion -ithin 58 )in o& the a+e6(redicted alue -as achieed in onl* 0< o&

our su9ects, i)(l*in+ that !R at "O7)a' is hi+hl* ariale a)on+ indiiduals. Al)ost 08 *r a+o,%u))in+ and Bor*s*? 1723 stated that the ran+e o& )a'i)al heart rate -as too ariale to use as a criterion

to con&ir) "O7)a'. Further)ore, the A)erican %olle+e o& S(orts Medicine 17@3 )andates that esti)ated

)a'i)al heart rates should not e used to identi&* an end(oint durin+ e'ercise testin+. There&ore, thiscriterion should not e used to con&ir) the attain)ent o& "O7)a'.

!o-eer, the ideal statistical assess)ent o& the suitailit* o& criteria to con&ir) "O7)a' is not to co)(are )ean

alues. "alid criteria -ould e characteried * not onl* ein+ related to a "O7(lateau ut also todiscri)inate et-een indiiduals -ho do and do not attain a (lateau. To date, no research desi+n and

a((ro(riate statistical assess)ent has een conducted on this to(ic.

In the (ast, the ter) "O7(ea? has een used rather interchan+eal* -ith "O7)a' to re&lect the hi+hest alue

attained &or )a'i)al o'*+en u(ta?e. Ro-ell 17;3 co))ented that "O7(ea? re(resents the hi+hest "O7

attained under s(eci&ic conditions, includin+ ar) or c*cle er+o)etr*, -hereas "O7)a' descries thehi+hest "O7alue achieed durin+ tread)ill e'ercise inolin+ at least @8 o& the )uscle )ass. In

addition, "O7)a' is co))onl* used -hen criteria are not satis&ied, althou+h little a+ree)ent e'ists as to

-hat the* reall* are. Also, it has een su++ested that "O7(ea? should re(resent s*)(to)6li)ited "O7durin+ e'ercise, and is not related to "O7)a'17>3. All in all, our estalish)ent o& -hat a((ear to e t-o

suitale criteria su((ort the notion that "O7(ea? should not e a((lied to health* su9ects e'ercisin+ to

olitional &ati+ue i& these criteria are )et. Ce reco))end that the ter) "O7(ea? should e used i& the "O7

(lateau and RER criteria are not )et.

All su9ects e'(ressed a (lateau in "O7durin+ the seere ! trial -hen +as e'chan+e data -ere otained reath6

*6reath or eer* 5@ s. This corroorates (reious -or? 17

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The (ri)ar* &indin+ o& the (resent inesti+ation -as that sa)(lin+ interals dra)aticall* in&luence the

incidence o& the "O7(lateau at "O7)a'. Chen shorter sa)(lin+ interals 155 reath and 5@ s aera+es3

-ere used, there -as 588 incidence o& a (lateau 1"O7@8 ))in3 in "O7at "O7)a' -ith an increase

in O7de)and. !o-eer, the "O7(lateau -as )ani&ested onl* @> and < o& the ti)e -hen +as

e'chan+e -as otained eer* 08 s and ;8 s, res(ectiel*. In addition, incidence o& the "O7(lateau -as

si)ilar &or ra)( and 0 )in ste( incre)ent (rotocols, as -ell as durin+ h*(o'ia e/uialent to 0,=88 )

altitude. T-o suitale criteria to con&ir) a((earance o& "O7)a' include a (lateau in "O7 @8 ))in andRER 5.5@ at "O7)a'. Because o& the estalish)ent o& these criteria, "O7(ea?should onl* e used to

descrie s*)(to)6li)ited "O7)a' in the asence o& a "O7(lateau or the RER criteria. In addition, it is

reco))ended that relatiel* short sa)(lin+ interals 1 5@ s3 e used to assess the "O7res(onse toincre)ental e'ercise to "O7)a'. The (resent &indin+s )a* lead scientists and clinicians to alter the

)ethodolo+* used in e'ercise testin+ to otain a etter assess)ent o& "O7)a'.

-eferences

5. Noa?es TD. Ma'i)al o'*+en u(ta?e4 classicalH ersus conte)(orar*H ie-(oints4 a reuttal.#e! Sci

S$%&t' "xe&c5==7=4@=5680.

> =458268

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50. Ro-land TC. Does (ea? "O7re&lect "O7)a'in children4 eidence &ro) su(ra)a'i)al testin+.#e! Sci

S$%&t' "xe&c5==07@4;2@4=0>62;.

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