nu ien s
A icle
Impac o he Me hod Used o Selec Gas Exchange
Da a o Es ima ing he Res ing Me abolic Ra e,
as Supplied by B ea h-by-B ea h Me abolic Ca s
Juan M.A. Alcan a a 1,* , Guille mo Sanchez-Delgado 1,2, F ancisco J. Ama o-Gahe e 1,3 ,
Jose E. Galgani 4and Jona an R. Ruiz 1
1
PROFITH “PROmo ing FITness and Heal h Th ough Physical Ac i i y” Resea ch G oup, Spo and Heal h
Uni e si y Resea ch Ins i u e (iMUDS), Depa men o Physical and Spo s Educa ion,
Facul y o Spo Sciences
, Uni e si y o G anada, 18011 G anada, Spain; gsanchezdelgado@ug .es (G.S.-D.);
ama o @ug .es (F.J.A.-G.); uizj@ug .es (J.R.R.)
2Penning on Biomedical Resea ch Cen e , Ba on Rouge, LA 70808, USA
3EFFECTS-262 Resea ch G oup, Depa men o Physiology, School o Medicine, Uni e si y o G anada,
18011 G anada, Spain
4Depa amen o de Ciencias de la Salud, Ca e a de Nu ición y Die é ica, Facul ad de Medicina,
Pon i icia Uni e sidad Ca ólica de Chile, San iago, Chile; Depa amen o de Nu ición, Diabe es y
Me abolismo, Facul ad de Medicina, Uni e sidad Pon i icia Ca ólica de Chile, 8330023 San iago, Chile.;
[email p o ec ed]
*Co espondence: alcan a ajma@ug .es; Tel.: +34-958-244-353
Recei ed: 23 Decembe 2019; Accep ed: 10 Feb ua y 2020; Published: 14 Feb ua y 2020


Abs ac :
The me hod used o selec ep esen a i e gas exchange da a om la ge da ase s in luences
he es ing me abolic a e (RMR) e u ned. This s udy de e mines which o h ee me hods yields he
lowes RMR (as ecommended o use in human ene gy balance s udies), and in which me hod he
g ea es a iance in RMR is explained by classical de e minan s o his a iable. A o al o 107 young
and 74 middle-aged adul s unde wen a 30 min RMR examina ion using a b ea h-by-b ea h me abolic
ca . Th ee gas exchange da a selec ion me hods we e used: (i) s eady s a e (SS ) o 3, 4, 5, o 10 min,
(ii) a p e-de ined ime in e al (TI), i.e., 6–10, 11–15, 16–20, 21–25, 26–30, 6–25, o 6–30 min, and (iii)
“ il e ing”, se ing h esholds depending on he mean RMR alue ob ained. In bo h coho s, he RMRs
yielded by he SS and il e ing me hods we e signi ican ly lowe (p<0.021) han hose yielded by he
TI me hod. No di e ences in RMR we e seen unde he di e en condi ions o he SS me hod, o o
he il e ing me hod. No di e ences we e seen be ween he me hods in e ms o he a iance in RMR
explained by i s classical de e minan s. In conclusion, he SS and il e ing me hods e u n he lowes
RMRs and in a-measu emen coe icien s o a ia ion when using b ea h-by-b ea h me abolic ca s.
Keywo ds:
es ing ene gy expendi u e; CCM exp ess; CPX Ul ima Ca diO2; indi ec calo ime y;
mac onu ien oxida ion
1. In oduc ion
The es ing me abolic a e (RMR) is he lowes ene gy expendi u e o a pe son who is awake [
1
],
a e a leas 12 h o as ing, being in physical es , and in a s a e o men al elaxa ion in an ambien
en i onmen al empe a u e; i accoun s o some 60–70% o he o al daily ene gy expendi u e [
2
].
The assessmen o RMR is impo an when s udying human ene gy balance, bo h in clinical and
esea ch se ings [
2
,
3
]. Indi ec calo ime y is he e e ence me hod o assessing RMR [
2
,
4
–
6
], which is
es ima ed om he consump ion o oxygen (VO
2
) and he p oduc ion o ca bon dioxide (VCO
2
) [
6
].
The measu emen o VO
2
and VCO
2
, oge he wi h u ina y ni ogen exc e ion, also allows o he
Nu ien s 2020,12, 487; doi:10.3390/nu12020487 www.mdpi.com/jou nal/nu ien s
Nu ien s 2020,12, 487 2 o 14
es ima ion o he nu ien (ca bohyd a e and a ) oxida ion a e [
7
]. Indeed, he VCO
2
/VO
2
a io,
i.e., he espi a o y quo ien (RQ), is an indica o o he ela i e p edominance o a (FATOx) and
ca bohyd a e (CHOOx) oxida ion.
The assessmen o RMR using indi ec calo ime y is no mally pe o med o e a 10–30 min pe iod.
I is widely assumed ha he i s 5 min o da a eco ded should be disca ded [
8
,
9
]. A sho (e.g., 5 min)
s eady espi a o y s a e pe iod, i.e., a pe iod in which he indi ec calo ime y eco d is ma kedly s able,
hen has o be selec ed om he emaining da ase o es ima ing he RMR [
6
,
7
,
10
]. The assump ion
ha s eady s a e (SS ) me hods o gas exchange da a selec ion p o ide a be e es ima e o RMR
han he o he me hods a ailable a ose om s udies pe o med in en ila ed pa ien s [
10
]. Howe e ,
he e is no s ong e idence ha he same can be assumed in heal hy, non- en ila ed subjec s—and
indeed di e en me hods ha e been used. These me hods can be g ouped in o h ee ca ego ies: (i) he
selec ion o an SS (de ined as ha p o iding a coe icien o a iance [CV] o <10% o VO
2
, VCO
2
, and
minu e en ila ion [VE], and o <5% o RQ [
11
]), (ii) he selec ion o a p e-de ined ime in e al (TI),
wi hou aking he s abili y o he esul s ob ained in o conside a ion [
11
], and (iii) “ il e ing”, in which
da a abo e o below a gi en RMR h eshold a e disca ded. Bo h he SS and TI me hods can be used
unde di e en ime condi ions [
1
]. Un o una ely, he use o di e en me hods o gas exchange da a
selec ion could esul in di e en es ima es o RMR and nu ien oxida ion a es being made [
1
,
11
,
12
].
Fo ins ance, in a s udy in ol ing heal hy subjec s, I ing e al. [
1
] epo ed RMR es ima es made by
he SS and TI me hods o di e by some −101 o +121 kcal/day.
Ce ainly, SS -based RMR es ima es a e usually lowe han hose p o ided by he TI me hod [
1
,
11
].
Gi en he abo e de ini ion o RMR [
1
], i has been p oposed ha he lowes es ima es ob ained by he
SS me hod should be deemed mo e accu a e han hose p o ided by TI. Howe e , he unde -es ima ion
o he homeos a ic RMR canno be uled ou in he SS me hod, no has any s udy checked whe he he
il e ing me hods o da a selec ion p o ide lowe RMR es ima es han ei he SS o TI.
The p esen wo k examines whe he he SS , TI, o il e ing me hod yields he lowes RMR
alue in heal hy, non- en ila ed subjec s, and de e mines in which me hod he g ea es a iance in
RMR is explained by he classical de e minan s o his a iable (i.e., body weigh , body composi ion,
and sex) [13].
2. Ma e ials and Me hods
2.1. S udy Subjec s
The pa icipan s o his e ospec i e s udy we e 107 young adul s (72 women) en olled in
he ACTIBATE s udy [
14
] and 74 middle-aged adul s (39 women) en olled in he FIT-AGEING
s udy [
15
]. De ailed in o ma ion abou he me hodology o he a o emen ioned s udies can be ound
elsewhe e [
14
,
15
]. B ie ly, he inclusion c i e ia we e: (i) being physically inac i e (<20 min o
mode a e– igo ous physical ac i i y on <3 days/week), (ii) ha ing a s able body weigh (change <3 kg
o e he las 3 mon hs [ACTIBATE] o <5 kg o e he las 5 mon hs [FIT-AGEING]), (iii) no being
en olled in a weigh loss p og am, (i ) no being a smoke , ( ) no su e ing om an acu e o ch onic
illness, and ( i) no being p egnan . The ACTIBATE s udy p o ocol was app o ed by he Commi ee
o Resea ch In ol ing Human Subjec s a he Uni e si y o G anada (Re e ence #924) and he Se icio
Andaluz de Salud (Cen o de G anada, CEI-G anada), while he FIT-AGEING was app o ed by he Human
Resea ch E hics Commi ee o he Jun a de Andaluc
í
a(0838-N-2017). Bo h s udies we e pe o med in
acco dance wi h he Decla a ion o Helsinki (2013 e ision) and egis e ed on he clinical ials.go
pla o m (IDs: NCT02365129 o he ACTIBATE s udy and NCT03334357 o he FIT-AGEING s udy).
O al and w i en in o med consen was ob ained om all he subjec s be o e hei en olmen .
2.2. P ocedu es
In bo h he abo e s udies, subjec s unde wen a 30 min indi ec calo ime y assessmen o RMR a
es , ea ly in he mo ning, ollowing an o e nigh as . All subjec s we e ins uc ed o e ain om
Nu ien s 2020,12, 487 3 o 14
mode a e (24 h) and igo ous physical ac i i y (48 h) be o e he es day. On he p e ious e ening,
all subjec s consumed a s anda dized meal o an egg omele , boiled ice, and oma o sauce (ad libi um
amoun s). They we e also ins uc ed o a oid physical ac i i y a e hey woke up, and o come o he
esea ch cen e by ca o bus ea ly in he mo ning, ha ing had no b eak as (ensu ing a ~
12 h as )
.
Upon a i al, and a e con i ming hei compliance wi h hese abo e condi ions, body weigh and
heigh we e measu ed using a Seca model 799 elec onic column scale (seca GmbH & Co. KG, Hambu g,
Ge many) wi h subjec s ba e oo and wea ing ligh clo hing. The ea e , he subjec s laid on a bed in
he supine posi ion o 20–30 min. Gas exchange da a we e hen eco ded by indi ec calo ime y o
30 min in a quie oom wi h dim ligh ing, con olled a 22–24
◦
C and 35–45% ela i e humidi y [
8
].
Du ing his ime he subjec s we e co e ed wi h a bed shee and ins uc ed o emain silen , s ay awake,
a oid idge ing, and o b ea he no mally.
2.3. Gas Exchange Assessmen s
Gas exchange was eco ded using ei he a CCM Exp ess o a CPX Ul ima Ca diO2 ( wo di e en
de ices we e used only in he middle-aged adul s coho ) b ea h-by-b ea h me abolic ca (Medical
G aphics Co p, S . Paul, MN, USA). Bo h ins umen s equi e he use o a ace mask equipped wi h a
Di ec connec
™
low senso (Medical G aphics Co p, S . Paul, MN, USA). Bo h de e mine VCO
2
using
a non-dispe si e in a ed analyze , and bo h de e mine VO
2
using a gal anic uel cell [
16
]. The low
a e was calib a ed using a 3 L sy inge a he beginning o e e y es . The gas analyze s we e calib a ed
be o e each measu emen using s anda d gases acco ding o he manu ac u e s’ ins uc ions [16].
2.4. Me hods o Gas Exchange Da a Selec ion
The collec ed gas exchange da a we e p ocessed using MGCDiagnos ic
®
B eeze Sui e 8.1.0.54
SP7 so wa e (Medical G aphics Co p., S . Paul, MN, USA) o yield a da a poin o each a iable o
e e y minu e (i.e., he means o all en ila ion da a (pe minu e en ila ion da a—pMVD) o each
pa icula minu e). The i s 5 min o da a we e disca ded [
8
,
9
]; he emaining 25 min pe iod da ase
was p ocessed using h ee di e en me hods o selec ep esen a i e gas exchange da a o de e mining
he RMR and nu ien oxida ion a e.
2.4.1. Time In e al Me hod
Sho TIs o 6–10 min, 11–15 min, 16–20 min, 21–25 min, and 26–30 min, and long TIs o 6–25 min
and 6–30 min we e es ablished [
11
], and he means o he pMVD alues o all a iables a ailable o
hese ime pe iods calcula ed. These p ocessed da a we e used o calcula e he RMR and nu ien
oxida ion a e (see below o de ails).
2.4.2. S eady-S a e Time Me hod
The CVs o VO
2
, VCO
2
, VE, and RQ we e calcula ed o e e y pe iod o 3, 4, 5, and 10 min
(e.g., o he 3 min
SS we p ocessed all he 25 min pe iod da ase s and we examined he 6 h o 8 h min
pe iod, he 7 h o 9 h pe iod, e c.) and he mean CVs o each a iable calcula ed o each ime pe iod.
The pe iods selec ed o he inal analyses we e hose wi h he lowes mean CV o each (e.g., om he
3 min SS examined pe iods, we selec ed he 7 h o 9 h) [
11
]. The means o he a ailable pMVD alues
o hese ime pe iods we e hen calcula ed. These p ocessed da a we e used o calcula e he RMR and
nu ien oxida ion a e (see below o de ails).
2.4.3. Fil e ing Me hod
The pMVD alues o VO
2
and VCO
2
o he en i e 25 min da a collec ion pe iod—i.e., wi h no
di ision in o SS o TI pe iods—we e used o calcula e he mean
25 min
RMR (see below o de ails).
Fu he mo e, pMVD RMR alues we e also calcula ed, disca ding ei he (i) hose alues <85% o
>115% o he mean
25 min
RMR (low il e ), (ii) <90% o >110% o he mean
25 min
RMR (medium il e ),
Nu ien s 2020,12, 487 4 o 14
o (iii) <95% o >105% o he mean
25 min
RMR (s ong il e ). Fo he minu es ha passed hese il e s,
he means we e calcula ed o all pMVD alues a ailable.
2.5. Calcula ing he Res ing Me abolic and Nu ien Oxida ion Ra es
Wei ’s equa ion (assuming ze o u ina y ni ogen exc e ion) [
17
] was used o calcula e RMR
alues om he mean pMVD o VO
2
and VCO
2
ob ained wi h each gas exchange da a selec ion
me hod. The FATOx and CHOOx a es we e calcula ed using F ayn’s s oichiome ic equa ions [
18
],
also assuming ze o u ina y ni ogen exc e ion. Finally, he mean RMR, RQ, VO
2
, VCO
2
, FATOx, and
CHOOx we e calcula ed o all gas exchange da a selec ion me hods unde each di e en condi ion.
2.6. Body Composi ion
Body composi ion was de e mined by dual ene gy X- ay abso p iome y using a Disco e y Wi
de ice (Hologic, Inc., Bed o d, MA, USA). Quali y con ols, he posi ioning o pa icipan s and analysis
o he esul s we e pe o med acco ding o he manu ac u e ’s ecommenda ions.
2.7. S a is ical analysis
Resul s a e p esen ed as mean
±
SD unless o he wise s a ed. All analyses we e conduc ed using
he S a is ical Package o he Social Sciences .22.0 (IBM SPSS S a is ics, IBM Co po a ion, Chicago,
IL, USA). Signi icance was se a p<0.05. Repea ed-measu es analysis o a iance (ANOVA) wi h a
pos -hoc Bon e oni es was used o de ec di e ences in RMR, RQ, VO
2
, VCO
2
, FATOx, and CHOOx
es ima es ac oss he me hods o gas exchange da a selec ion. The CVs o VO
2
, VCO
2
, RQ, and VE
ob ained ia he di e en me hods we e also compa ed. Two di e en ANOVA models we e used:
one wi h ou le els o ixed ac o s (i.e., sho TI, long TI, SS , and il e ing), and one wi h 14 le els
(all me hods and hei di e en condi ions).
The di e ences be ween he me hods in e ms o he a iance in RMR explained by i s classical
de e minan s (i.e., body weigh , body composi ion [lean and a masses], and sex) [
13
] we e examined
by ei he simple linea eg ession (associa ions be ween RMR and body weigh ) o mul iple linea
eg ession (associa ions be ween RMR and sex and body weigh ; RMR and sex and lean and a masses).
3. Resul s
Table 1p o ides desc ip i e da a o he subjec s in bo h coho s.
Table 1. Subjec desc ip i e cha ac e is ics.
Young Adul s (n=107) Middle-Aged Adul s (n=74)
Min Max Pe cen ile
10–90 Min Max Pe cen ile
10–90
Age (yea s) 22.2 ±2.2 18.2 26.6 19.1–25.2 53.5 ±5.3 45.0 66.0 47.0–61.7
Sex (n%)
Women 72, 67 39, 53
35, 47
Men 35, 33
Me abolic ca used (n%)
CCM Exp ess 46, 43
61, 57
69.3 ±15.9
167.8 ±8.7
24.5 ±4.4
79.8 ±13.2
41.4 ±9.5
24.0 ±8.9
35.0 ±7.8
0, 0
CPX Ul ima Ca diO2 74, 100
Body weigh (kg) 45.0 118.5 52.2–90.6 75.7 ±15.0
167.8 ±9.8
26.7 ±3.8
95.1 ±11.7
43.5 ±11.7
30.0 ±8.4
39.9 ±9.1
50.6 110.7 57.8–94.6
Heigh (cm) 148.5 195.1 157.2–180 148.3 189.8 155.8–181.6
BMI (kg/m2)17.2 38.4 19.4–30.9 19.0 38.0 22.0–31.7
Wais ci cum e ence (cm) 58.0 125.6 65.0–97.8 68.6 118.7 79.2–107.8
Lean mass (kg) 28.1 66.8 31.0–55.2 22.7 63.6 30.5–59.6
Fa mass (kg) 9.9 51.7 14.6–36.4 14.5 55.8 20.6–40.7
Fa mass (%) 15.3 51.9 26.2–44.4 23.0 59.4 26.7–51.1
Da a a e p esen ed as mean ±SD unless o he wise s a ed.
Nu ien s 2020,12, 487 5 o 14
3.1. In luence o he Gas Exchange Da a Selec ion Me hod on Es ima es o RMR, RQ and Nu ien Oxida ion
Figu e 1shows he RMR and RQ es ima es yielded by he gas exchange da a selec ion me hods o
bo h he young and middle-aged adul s. In he young adul s, he sho and long TI me hods p o ided
highe mean RMR es ima es han ei he he SS o il e ing me hods ( aking all condi ions oge he ;
pos -hoc Bon e oni p<0.001; Figu e 1A). In he middle-aged adul s hey also p o ided highe mean
RMR es ima es han he il e ing me hod ( aking all condi ions oge he ; pos -hoc Bon e oni p<0.001;
Figu e 1B). No di e ences we e seen be ween he RMR es ima es yielded by he sho and long TIs, no
be ween he SS and he il e ing me hods ( aking all condi ions oge he ) in ei he he young o he
middle-aged adul s (all pos -hoc Bon e oni p=1.000; Figu e 1A,B). Fo he young adul s, he lowes
mean RMR alues we e ob ained wi h he SS 4 min me hod (1440 kcal/day; Figu e 1E); howe e ,
he SS 4 min me hod was only s a is ically di e en om he TI 6–10 min and he TI 11–15 min.
In he middle-aged adul s he lowes mean RMR alues we e p o ided by he s ong- il e me hod
(1493 kcal/day; Figu e 1F); he s ong- il e me hod was s a is ically di e en om all he di e en
me hods, wi h he excep ion o he TI 11–15 min, and he SS 3, 4, and 5 min condi ions. Table S1
shows he compa isons (i.e., pos -hoc Bon e oni) be ween he di e en me hods. Simila pa e ns
we e obse ed when analyzing he in luence o gas exchange da a selec ion me hod on VO
2
and VCO
2
es ima es (Figu e S1).
Las ly, he pe iods in which he SS we e achie ed (wi h he di e en SS me hods applied) in he
young and he middle-aged adul s a e p esen ed in Figu e S2. We obse ed ha ~50% o young and
middle-aged adul s achie ed hei SS s (i.e., he one p esen ing lowe mean CV) du ing he i s hal o
he 30 min indi ec calo ime y assessmen . On he o he hand, we ound di e ences be ween he i s
s eady s a e achie ed (i.e., he i s pe iod in which he CVs o VO
2
<10, VCO
2
<10, VE <10, and
RQ <5) and he “bes ” SS achie ed (i.e., he pe iod wi h he lowes mean CVs) in RMR es ima ion in
young adul s (Figu e S3).
The RQ es ima es yielded by he sho TI me hod we e signi ican ly highe han all o he s in he
young adul coho (all pos -hoc Bon e oni p<0.002; Figu e 1C) and ha il e ing me hod ( aking
all condi ions oge he ) in he middle-aged adul s coho (pos -hoc Bon e oni p=0.038; Figu e 1D).
Mo eo e , he long TI me hod p o ided highe RQ es ima es han he SS and il e ing me hods
( aking all condi ions oge he ) in he young adul (bo h Bon e oni pos -hoc p<0.013; Figu e 1C).
No di e ences in RQ es ima es we e seen when compa ing he SS and il e ing me hods ( aking all
condi ions oge he ) in ei he he young o he middle-aged adul s (pos -hoc Bon e oni p=1.000;
Figu e 1C,D). Fu he mo e, he long TI and he SS we e no signi ican ly di e en han ei he he
sho TI me hod o he il e ing me hods ( aking all condi ions oge he ) in he middle-aged adul s
(Figu e 1D). The lowes mean RQ alues we e ob ained when using he s ong- il e me hod (0.84) in
he young adul s (Figu e 1G). Howe e , he s ong- il e me hod was only s a is ically di e en om
he TI 26–30 min and he TI 6–30 min. The lowes mean RQ alues we e ob ained when using he SS
3 min me hod (0.80) in he middle-aged adul s (Figu e 1H). Howe e , no s a is ical di e ences we e
obse ed. As expec ed, he da a selec ion me hods yielding highe RQ es ima es also p o ided highe
CHOOx and lowe FATOx es ima es, and ice e sa (Figu e 2).

Nu ien s 2020,12, 487 6 o 14
Nu ien s 2020, 12, 487 6 o 14
Figu e 1. Di e ences among gas exchange da a selec ion me hods wi h espec o es ing me abolic
a e (RMR) and espi a o y quo ien (RQ) es ima es. Black columns ep esen sho ime in e al (TI)
pe iods (i.e., he means o he pe minu e en ila ion da a (pMVD]) alues o all a iables a ailable
o hese ime pe iods, panels A–D; he pMVD alues o each sho TI pe iod, panels E,F). Ligh g ey
columns ep esen long TI pe iods (i.e., he means o he pMVD alues o all a iables a ailable o
hese ime pe iods, panels A–D; he means o he pMVD alues o each long TI pe iod, panels E,F).
Whi e columns ep esen s eady s a e (SS ) pe iods (i.e., he means o he pMVD alues o all
a iables a ailable o hese SS pe iods, panels A–D; he means o he pMVD alues o each SS
pe iod, panels E,F). Da k g ey columns ep esen il e ing me hods (i.e., he means o he pMVD
alues o all a iables a ailable o hese il e ing pe iods, panels A–D; he means o he pMVD
alues o each il e ing pe iod, panels E,F). p- alues come om epea ed-measu es analysis o
a iance (ANOVA). Iden ical indica o y le e s highligh di e ences as de e mined by pos -hoc
Bon e oni analysis. Da a a e p esen ed as mean and s anda d e o o he mean (SEM). Min: minu es;
VCO2: p oduc ion o ca bon dioxide; VO2: consump ion o oxygen.
Figu e 1.
Di e ences among gas exchange da a selec ion me hods wi h espec o es ing me abolic
a e (RMR) and espi a o y quo ien (RQ) es ima es. Black columns ep esen sho ime in e al (TI)
pe iods (i.e., he means o he pe minu e en ila ion da a (pMVD]) alues o all a iables a ailable
o hese ime pe iods, panels
A
–
D
; he pMVD alues o each sho TI pe iod, panels
E
,
F
). Ligh
g ey columns ep esen long TI pe iods (i.e., he means o he pMVD alues o all a iables a ailable
o hese ime pe iods, panels
A
–
D
; he means o he pMVD alues o each long TI pe iod, panels
E,F
). Whi e columns ep esen s eady s a e (SS ) pe iods (i.e., he means o he pMVD alues o all
a iables a ailable o hese SS pe iods, panels
A
–
D
; he means o he pMVD alues o each SS pe iod,
panels
E
,
F
). Da k g ey columns ep esen il e ing me hods (i.e., he means o he pMVD alues o
all a iables a ailable o hese il e ing pe iods, panels A–D; he means o he pMVD alues o each
il e ing pe iod, panels
E
,
F
). p- alues come om epea ed-measu es analysis o a iance (ANOVA).
Iden ical indica o y le e s highligh di e ences as de e mined by pos -hoc Bon e oni analysis. Da a
a e p esen ed as mean and s anda d e o o he mean (SEM). Min: minu es; VCO
2
: p oduc ion o
ca bon dioxide; VO2: consump ion o oxygen.
Nu ien s 2020,12, 487 7 o 14
Nu ien s 2020, 12, 487 7 o 14
The RQ es ima es yielded by he sho TI me hod we e signi ican ly highe han all o he s in he
young adul coho (all pos -hoc Bon e oni p < 0.002; Figu e 1C) and ha il e ing me hod ( aking all
condi ions oge he ) in he middle-aged adul s coho (pos -hoc Bon e oni p = 0.038; Figu e 1D).
Mo eo e , he long TI me hod p o ided highe RQ es ima es han he SS and il e ing me hods
( aking all condi ions oge he ) in he young adul (bo h Bon e oni pos -hoc p < 0.013; Figu e 1C). No
di e ences in RQ es ima es we e seen when compa ing he SS and il e ing me hods ( aking all
condi ions oge he ) in ei he he young o he middle-aged adul s (pos -hoc Bon e oni p = 1.000;
Figu e 1C,D). Fu he mo e, he long TI and he SS we e no signi ican ly di e en han ei he he
sho TI me hod o he il e ing me hods ( aking all condi ions oge he ) in he middle-aged adul s
(Figu e 1D). The lowes mean RQ alues we e ob ained when using he s ong- il e me hod (0.84) in
he young adul s (Figu e 1G). Howe e , he s ong- il e me hod was only s a is ically di e en om
he TI 26–30 min and he TI 6–30 min. The lowes mean RQ alues we e ob ained when using he SS
3 min me hod (0.80) in he middle-aged adul s (Figu e 1H). Howe e , no s a is ical di e ences we e
obse ed. As expec ed, he da a selec ion me hods yielding highe RQ es ima es also p o ided highe
CHOOx and lowe FATOx es ima es, and ice e sa (Figu e 2).
Figu e 2.
Di e ences among gas exchange da a selec ion me hods wi h espec o a oxida ion (FATOx)
and ca bohyd a e oxida ion (CHOOx) a es. Black columns ep esen sho ime in e al (TI) pe iods
(i.e., he means o he pe minu e en ila ion da a [pMVD] alues o all a iables a ailable o hese
ime pe iods, panels
A
–
D
; he pMVD alues o each sho TI pe iod, panels
E
,
F
). Ligh g ey columns
ep esen long TI pe iods (i.e., he means o he pMVD alues o all a iables a ailable o hese ime
pe iods, panels
A
–
D
; he means o he pMVD alues o each long TI pe iod, panels
E
,
F
). Whi e columns
ep esen s eady s a e (SS ) pe iods (i.e., he means o he pMVD alues o all a iables a ailable o
hese SS pe iods, panels
A
–
D
; he means o he pMVD alues o each SS pe iod, panels
E
,
F
). Da k
g ey columns ep esen il e ing me hods (i.e., he means o he pMVD alues o all a iables a ailable
o hese il e ing pe iods, panels
A
–
D
; he means o he pMVD alues o each il e ing pe iod, panels
E
,
F
). p- alues come om epea ed-measu es analysis o a iance (ANOVA). Iden ical indica o y le e s
highligh di e ences as de e mined by pos -hoc Bon e oni analysis. Da a a e p esen ed as mean and
s anda d e o o he mean (SEM). Min: minu es.
Nu ien s 2020,12, 487 8 o 14
3.2. Di e ences be ween he Me hods in Te ms o he Va iance in RMR Explained by I s Classical De e minan s
The a iance in RMR explained by body weigh ( aking all condi ions oge he ) was 36%, 36%,
34% and 38% o he sho TI, long TI, SS , and il e ing me hods espec i ely in young adul s, and
50%, 51%, 52% and 51% espec i ely in he middle-aged adul s. The mos explained a iance was
ob ained using he low- il e me hod (40%) in young adul s and he TI 6–10 min me hod (54%) in he
middle-aged adul s.
The a iance explained inc eased o 34–45% and 54–68% in he young and middle-aged adul s
espec i ely a e including subjec sex in he model (Table 2). The mos explained a iance was
ob ained wi h he low- il e me hod in young adul s, and bo h he TI 21–25 min and he medium- il e
me hods in he middle-aged adul s. Howe e , li le di e ence was seen among he me hods in e ms
o he a iance explained by he classical de e minan s o RMR (Table 2).
A u he model including subjec sex, lean, and a masses inc eased he a iance in RMR
explained by ~5% in he young adul s, bu no in he middle-aged adul s (Table 3). The low- il e
me hod explained he g ea es a iance in RMR in he young adul s, and he TI 21–25 min me hod did
so in he middle-aged adul s. Howe e , once again, li le di e ence was seen among he me hods in
e ms o he a iance explained by he classical de e minan s o RMR (Table 3).
Nu ien s 2020,12, 487 9 o 14
Table 2. Va iance in es ing me abolic a e (RMR) explained by sex and body weigh in each o he gas exchange da a selec ion me hods.
Me hod o Da a Selec ion
Young Adul s (n=107) Middle-Aged Adul s (n=74)
Sex Weigh (kg) Sex Weigh (kg)
Model R2Cons an βpβpModel R2Cons an βpβp
TI 6–10 min 0.44 1232 −171.6 0.001 7.8 <0.001 0.67 1503 −424.0 0.001 8.9 0.001
TI 11–15 min 0.40 1340 −214.4 <0.001 7.3 <0.001 0.67 1616 −418.5 0.001 7.1 0.004
TI 16–20 min 0.40 1300 −214.5 <0.001 7.6 <0.001 0.60 1758 −445.2 0.001 6.2 0.031
TI 21–25 min 0.36 1342 −199.5 0.001 6.7 <0.001 0.68 1935 −507.5 0.001 4.9 0.051
TI 26–30 min 0.34 1208 −155.7 0.009 7.5 <0.001 0.54 1754 −409.8 0.001 5.5 0.058
TI 6–30 min 0.42 1284 −191.2 0.001 7.4 <0.001 0.66 1713 −441.0 0.001 6.5 0.010
TI 6–25 min 0.43 1303 −200.0 <0.001 7.3 <0.001 0.67 1703 −448.8 0.001 6.8 0.008
SS 3 min 0.39 1245 −194.9 0.001 7.8 <0.001 0.66 1669 −456.7 0.001 7.1 0.008
SS 4 min 0.39 1169 −167.5 0.004 7.9 <0.001 0.67 1786 −481.1 0.001 6.4 0.016
SS 5 min 0.36 1301 −207.0 0.001 7.1 <0.001 0.66 1763 −464.1 0.001 6.2 0.016
SS 10 min 0.41 1232 −182.8 0.001 7.7 <0.001 0.66 1681 −443.8 0.001 7.0 0.008
Low- il e 0.45 1188 −170.6 0.001 8.1 <0.001 0.67 1701 −442.9 0.001 6.6 0.009
Medium- il e 0.43 1209 −170.8 0.001 7.8 <0.001 0.68 1725 −447.5 0.001 6.4 0.010
S ong- il e 0.44 1218 −182.0 0.001 7.7 <0.001 0.67 1684 −431.7 0.001 6.2 0.012
Uns anda dized be a and p- alues (signi ican alues in bold) om mul iple eg ession analyses, in which sex and body weigh we e included as independen a iables, and he RMR
es ima es yielded by he di e en me hods o gas exchange da a selec ion we e included as dependen a iables. Sex: 1 =men; 2 =women.