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Recommenda ions o De e mining he Validi y o Consume Wea ables and
Sma phones o he Es ima ion o Ene gy Expendi u e : Expe S a emen and Checklis
o he INTERLIVE Ne wo k
© Au ho s, 2022
Published e sion
A gen , Rob; He he ing on-Rau h, Megan; S ang, Julie; Ta p, Jakob; O ega,
F ancisco B.; Molina-Ga cia, Pablo; Schumann, Mo i z; Bloch, Wilhelm; Cheng,
Sulin; G øn ed, Ande s; B ønd, Jan Ch is ian; Ekelund, Ul ; Sa dinha, Luis B.;
Caul ield, B ian
A gen , R., He he ing on-Rau h, M., S ang, J., Ta p, J., O ega, F. B., Molina-Ga cia, P.,
Schumann, M., Bloch, W., Cheng, S., G øn ed, A., B ønd, J. C., Ekelund, U., Sa dinha, L. B., &
Caul ield, B. (2022). Recommenda ions o De e mining he Validi y o Consume Wea ables and
Sma phones o he Es ima ion o Ene gy Expendi u e : Expe S a emen and Checklis o he
INTERLIVE Ne wo k. Spo s Medicine, 52(8), 1817-1832. h ps://doi.o g/10.1007/s40279-022-
01665-4
2022
Vol.:(0123456789)
Spo s Medicine
h ps://doi.o g/10.1007/s40279-022-01665-4
SYSTEMATIC REVIEW
Recommenda ions o De e mining heValidi y o Consume
Wea ables andSma phones o  heEs ima ion o Ene gy Expendi u e:
Expe S a emen andChecklis o  heINTERLIVE Ne wo k
RobA gen 1,2,3 · MeganHe he ing on‑Rau h4· JulieS ang5· JakobTa p5· F anciscoB.O ega6,7·
PabloMolina‑Ga cia6· Mo i zSchumann8,9· WilhelmBloch8· SulinCheng8,9,10· Ande sG øn ed11·
JanCh is ianB ønd11· Ul Ekelund5· LuisB.Sa dinha4· B ianCaul ield1,2
Accep ed: 15 Feb ua y 2022
© The Au ho (s) 2022
Abs ac
Backg ound Consume wea ables and sma phone de ices commonly o e an es ima e o ene gy expendi u e (EE) o assis
in he objec i e moni o ing o physical ac i i y o he gene al popula ion. Alongside consume s, heal hca e p o essionals
and esea che s a e seeking o u ilise hese de ices o he moni o ing o aining and imp o ing human heal h. Howe e ,
he me hods o alida ion and epo ing o EE es ima ion in hese de ices lacks igou , nega i ely impac ing on he abili y
o make compa isons be ween de ices and p o ide anspa en accu acy.
Objec i es The Towa ds In elligen Heal h and Well-Being Ne wo k o Physical Ac i i y Assessmen (INTERLIVE) is a
join Eu opean ini ia i e o six uni e si ies and one indus ial pa ne . The ne wo k was ounded in 2019 and s i es owa ds
de eloping bes -p ac ice ecommenda ions o e alua ing he alidi y o consume wea ables and sma phones.This expe
s a emen p esen s a bes -p ac ice alida ion p o ocol o consume wea ables and sma phones in he es ima ion o EE.
Me hods The ecommenda ions we e de eloped h ough (1) a sys ema ic li e a u e e iew; (2) an uns uc u ed e iew o he
wide li e a u e discussing he po en ial ac o s ha may in oduce bias du ing alida ion s udies; and (3) e idence-in o med
expe opinions om membe s o he INTERLIVE ne wo k.
Resul s The sys ema ic li e a u e e iew p ocess iden i ied 1645 po en ial a icles, o which 62 we e deemed eligible o
he inal da ase . Based on hese s udies and he wide li e a u e sea ch, a alida ion amewo k is p oposed encompassing
six key domains o alida ion: he a ge popula ion, c i e ion measu e, index measu e, es ing condi ions, da a p ocessing
and he s a is ical analysis.
Conclusions The INTERLIVE ne wo k ecommends ha he p oposed p o ocol, and checklis s p o ided, a e used o s and-
a dise he es ing and epo ing o he alida ion o any consume wea able o sma phone de ice o es ima e EE. This in
u n will maximise he po en ial u ili y o hese echnologies o clinicians, esea che s, consume s, and manu ac u e s/
de elope s, while ensu ing anspa ency, compa abili y, and eplicabili y in alida ion.
T ial Regis a ion PROSPERO ID: CRD42021223508.
* Rob A gen
ob.a [email p o ec ed]
Ex ended au ho in o ma ion a ailable on he las page o he a icle
1 In oduc ion
Wo ldwide, he numbe o consume wea able de ices sold
in 2020 is es ima ed o ha e eached almos 400 million
uni s [1]. The g owing popula i y o hese de ices, com-
bined wi h he numbe o sma phone use s oday su passing
3 billion [2], means ha mo e people han e e a e able o
sel -moni o hei physical heal h and ac i i y. Addi ion-
ally, consume wea ables a e being inc easingly u ilised
in heal hca e and esea ch se ings [3]. These de ices can
assess a a ie y o me ics associa ed wi h physical ac i i y
including s ep coun , hea a e, maximal oxygen consump-
ion (VO2max), and ene gy expendi u e (EE).
T adi ionally, he measu emen o EE has been conduc ed
ia indi ec calo ime y (whe e gaseous exchange is meas-
u ed and con e ed o EE using s anda d o mulae such as
he Wei Equa ion [4]), di ec calo ime y ( he measu emen
o hea p oduc ion by he body), o doubly labelled wa e
R.A gen e al.
Key Poin s
This sys ema ic li e a u e e iew o alida ion s udies o
consume wea ables and sma phone applica ions has
highligh ed a he e ogenei y be ween alida ion me hod-
ologies in key domains, pa icula ly in he a ge popula-
ions, da a p ocessing and s a is ical app oaches, gi ing
ise o alida ion bias.
The lack o ee-li ing alida ion leads o limi ed abili-
ies o use s o unde s and he accu acy o wea able
de ices and sma phones in es ima ing ene gy expendi-
u e (EE) in he in ended use case.
In his a icle, he INTERLIVE ne wo k p o ides bes -
p ac ice ecommenda ions o be used in u u e p o o-
cols o mo e owa ds a mo e accu a e, anspa en and
compa able alida ion o EE es ima ion de i ed om
consume wea ables and sma phone applica ions.
di icul o consume s and clinicians o na iga e he ma ke
and unde s and o compa e he accu acy o such de ices
[13]. Whe he a consume moni o can be conside ed accu-
a e o es ima ing EE is de e mined by a combina ion o
he a ge popula ion, he in ended ou pu (daily TEE, daily
AEE, aining session EE, aining session AEE, e c.) and
he ans e abili y o he alida ion p o ocol o he in ended
use. Fo example, a consume moni o wi h epo ed high
accu acy du ing an inc emen al walking o unning p o ocol
may no be he igh choice o an indi idual who expends
ene gy abo e es , p ima ily du ing less o mal ac i i ies.
As consume moni o s will be used o a ange o pu poses,
a comp ehensi e e alua ion du ing disc e e ac i i ies and
ee-li ing se ings is needed o maximise applicabili y.
The e ha e been calls o s anda disa ion o he e alua-
ion o consume wea able de ices, wi h eques s o ma -
ke ing claims om manu ac u e s o be e idence-based and
independen ly e i ied in a anspa en manne wi h app o-
p ia e analy ical app oaches [14, 15]. While amewo ks
ha e been p oposed o e alua e wea ables ac oss he mos
commonly measu ed me ics, such as s ep coun , hea a e,
EE and VO2 max [13, 16], he majo i y o hese ela e o
esea ch-g ade de ices. To add ess he challenges discussed,
he Towa ds In elligen Heal h and Well-Being Ne wo k o
Physical Ac i i y Assessmen (INTERLIVE) ne was es ab-
lished o in eg a e and build upon p e ious wo k o p opose
bes -p ac ice p o ocols o he alida ion o exe cise/ac i -
i y me ic measu emen capabili ies in consume wea ables
and sma phones. In his case, INTERLIVE is add essing
he measu emen o EE. The ne wo k i s conduc ed a sys-
ema ic li e a u e e iew o iden i y he me hods p e iously
used in he alida ion o EE es ima ion in consume wea a-
bles and sma phones. Following his, o he ele an li e a-
u e discussing ac o s ha may in oduce bias in alida ion
s udies was hen consul ed, alongside e idence-in o med
ne wo k discussion o de elop bes -p ac ice alida ion ec-
ommenda ions. This pape p esen s a comp ehensi e epo
on he a iables o conside when designing and conduc -
ing alida ion p o ocols o he es ima ion o EE and makes
ecommenda ions o he bes p ac ice me hodologies and
epo ing o such s udies.
2 Expe S a emen P ocess
2.1 The INTERLIVE Ne wo k
INTERLIVE is a join ini ia i e o he Uni e si y o Lisbon
(Po ugal), Ge man Spo Uni e si y (Ge many), Uni e -
si y o Sou he n Denma k (Denma k), No wegian School
o Spo Sciences (No way), Uni e si y College Dublin (I e-
land), Uni e si y o G anada (Spain) and Huawei Technolo-
gies, Finland. The ne wo k was ounded in 2019, comp ising
(DLW; whe e u ine samples a e analysed using iso ope a io
mass spec ome y) [5, 6]. While DLW is conside ed he
gold s anda d o measu ing ee-li ing EE [6, 7], i only
p o ides a measu e o o al EE (TEE), and he ac i e EE
(AEE) is de e mined by sub ac ing an es ima e o he es -
ing EE. Addi ionally, DLW is an expensi e and complex
app oach, equi ing specialis skills and esou ces. The e-
o e, indi ec calo ime y has been he p edominan c i e ion
measu e o AEE in ecen yea s [6]. Howe e , hese indi ec
calo ime y me hodologies a e limi ed o mo e con olled
p o ocols equi ing he use o me abolic ca s, which a e
expensi e and equi e echnical skills o adminis e .
The widesp ead a ailabili y, ela i ely low cos , and
wea abili y o consume ac i i y moni o s means ha da a
ha could only be cap u ed in specialis se ings a e now
a ailable o he gene al popula ion, and hese de ices a e
inc easingly being used o p o ide measu es o EE. Mos
use s seek his in o ma ion o ei he AEE in moni o ing
calo ie consump ion du ing a speci ic exe cise ac i i y, o
o suppo hem wi h hei TEE ac oss a day, possibly in
he managemen o die o weigh loss. A a ie y o inpu s,
including use demog aphics such as age, sex, weigh and
heigh , and da a om on-boa d senso s, including accele -
ome e s and/o pho ople hysmog aphy hea a e senso s,
a e used o make es ima es o EE [8–10]. Howe e , he
alidi y and eliabili y o consume wea ables o es ima e
g oup- and indi idual-le el EE is subjec o deba e, wi h
nume ous alida ion s udies being conduc ed, o e ing a y-
ing me hodologies and esul s [11, 12]. The inconsis ency
in alida ion p o ocols used in he li e a u e, along wi h a
lack o anspa ency in epo ing s anda ds means ha i is
De e mining Validi y o Wea ables o Es ima ion o Ene gy Expendi u e
o he au ho s o his pape , plus addi ional expe s wi hin
each ins i u ion, and s i es owa ds de eloping bes -p ac ice
p o ocols o e alua ing he alidi y o consume wea a-
bles wi h ega d o measu emen o exe cise/ac i i y me -
ics. Mo eo e , we a e aiming o inc ease awa eness o he
ad an ages and limi a ions o di e en alida ion me hods
and o in oduce no el heal h- ela ed me ics, os e ing a
widesp ead use o physical ac i i y indica o s. To da e, bes -
p ac ice alida ion p o ocols o consume wea able hea
a e moni o ing [17] and s ep-coun ing [18] ha e been p o-
posed by he ne wo k. In his pape , we de ail INTERLIVE’s
wo k in espec o he measu emen o EE.
2.2 Expe Valida ion P o ocol De elopmen
2.2.1 Expe Valida ion P ocess
The ne wo k used he same p ocess o de elop he bes -
p ac ice alida ion p o ocols o he consume wea able
de ice-de i ed me ics as was used o he p e ious HR
moni o ing and s ep-coun ing pa ame e s [17, 18]. The i s
s ep o de eloping he expe ecommenda ions consis ed
o a sys ema ic e iew o he alida ion p o ocols used in he
scien i ic li e a u e. This in o ma ion was hen used as he
ounda ion o discussions and o p o ide ecommenda ions
on he op imal and mos easible p o ocol o assessing he
alidi y o consume wea ables. Wo king g oup mee ings
we e held o discuss he aspec s o he alida ion p o ocols
used in he s udies iden i ied in he sys ema ic sea ch. A
se o key domains o bes -p ac ice ecommenda ions we e
p oposed based on he ou comes o he sys ema ic li e a u e
e iew, he a p io i knowledge ela ing o esea ch g ade
de ice alida ion [13, 16, 19, 20], and he e idence-in o med
expe opinion o he INTERLIVE membe s. The syn he-
sised da a we e hen e iewed wi h espec o hese domains,
and expe alida ion p o ocols o he consume wea able-
de i ed EE me ic was hen de eloped by he wo king g oup.
2.2.2 Sys ema ic Re iew P ocess
The p ima y aim o he sys ema ic li e a u e e iew was o
de e mine which me hods and p o ocols a e cu en ly being
used in he scien i ic li e a u e o alida e he consume
wea able o sma phone-de i ed me ic o EE. I was beyond
he scope o his e iew o explo e he esul s o he included
s udies, al hough a ecen sys ema ic e iew and me a-anal-
ysis was published, wi h accu acy a ying dependen on
ac i i y ype [11]. The sea ch was conduc ed wi h espec
o he P e e ed Repo ing I ems o Sys ema ic Re iews
and Me a-Analyses (PRISMA) s a emen and egis e ed
wi h he in e na ional da abase o p ospec i ely egis e ed
sys ema ic e iews in heal h and social ca e (PROSPERO
ID: CRD42021223508). To iden i y pee - e iewed jou nal
a icles, we sea ched he PubMed, Web o Science, and Sco-
pus elec onic da abases using speci ic sea ch e ms, which
a e lis ed in elec onic supplemen a y Table1.
To be included o e iew, he s udies had o (1) be pub-
lished p io o 4 Decembe 2020; (2) examine he alidi y o
consume -based wea able and sma phone applica ions o
es ima ing EE compa ed wi h he gold-s anda d c i e ion
measu e o ei he di ec o indi ec calo ime y, me abolic
chambe , o DLW; and (3) be w i en in English. S udies
we e excluded i he index measu e was no de i ed om
da a acqui ed using a consume wea able de ice o sma -
phone, did no con ain a alida ion p o ocol, he e was no
gold-s anda d c i e ion measu e, he ou come assessed by
he de ice was no EE, o i he ull ex was no a ailable.
Fo ou pu poses, wea ables we e es ic ed o only hose
wi h a consume pu pose a he han a esea ch o clinical
pu pose, meaning ha he de ices a e p ima ily ma ke ed
o he consume and a e eadily a ailable o pu chase and
use by membe s o he public. No exclusion c i e ia we e
se o he s udy popula ion (i.e., heal hy, clinical pa ien s,
child en). The sys ema ic li e a u e e iew p ocess was con-
duc ed by RA, MHR, JS, and JT. Ti le/abs ac and ull- ex
sc eening we e comple ed by wo independen e iewe s and
con i med by a hi d independen e iewe using Co idence
so wa e (Ve i as Heal h Inno a ion) [21].
A cus om-designed sp eadshee was used o da a ex ac-
ion and included he ollowing headings: sample size
included/analysed, sex dis ibu ion, ype o popula ion,
body mass index (BMI), heigh , weigh , age, condi ion ype
(labo a o y; semi- ee-li ing; ee-li ing), c i e ion measu e
(desc ip ion, con igu a ion and placemen ), index measu e
(desc ip ion, con igu a ion and placemen ), es ing p o ocol,
signal p ocessing, da a synch onisa ion, s a is ical analysis,
esul s and conclusions. Valida ion p o ocols we e di ided
in o h ee ca ego ies based on he ollowing de ini ions:
Labo a o y: Well-con olled condi ions, p edominan ly
asks such as walking o unning on a eadmill/indoo /ou -
doo en i onmen , o cycling on a s a iona y cycle e gome e
a p e-de ined o sel -selec ed speeds.
Semi ee-li ing: Semi-con olled condi ions, including
‘simula ed’ ac i i ies o daily li ing o he pu pose o epli-
ca ing ‘ ee-li ing’ condi ions (e.g. sweeping, cooking, old-
ing laund y, compu e use, spo -speci ic ac i i y).
F ee-li ing: Uncon olled me hodologies ha in ol e pa -
icipan s wea ing he index de ice du ing ‘no mal’ daily li e,
ou side o a con olled labo a o y o simula ed en i onmen .
3 Cu en S a e o Knowledge
The sea ch s a egy o his sys ema ic e iew yielded 1645
po en ial a icles o inclusion. Following he emo al o 371
duplica es, 1275 i les and abs ac s we e sc eened, esul ing
R.A gen e al.
in 254 a icles ha me he c i e ia o ull- ex sc eening.
O e all, 192 s udies we e excluded, esul ing in a inal o al
o 62 s udies accep ed o da a ex ac ion. O he 192 exclu-
sions, 174 we e excluded as hey did no e alua e consume
wea ables and ins ead assessed clinical and esea ch-g ade
de ices. The PRISMA lowcha o he s ages o he sys-
ema ic sea ch and sc eening p ocess, including easons o
exclusion, is illus a ed in Fig.1.
The ull ex ac ion da a p esen ing he me hodologies
employed ac oss he included s udies can be ound in elec-
onic supplemen a y Table2 (labo a o y p o ocols), elec-
onic supplemen a y Table3 (semi- ee-li ing p o ocols),
and elec onic supplemen a y Table4 ( ee-li ing p o ocols).
Eigh y- i e di e en models om 35 manu ac u e s we e
epo ed in a icles included in his sys ema ic e iew, he
majo i y being wea able manu ac u e s (n = 30), wi h only
i e sma phone applica ions e alua ed. The mos s udied
manu ac u e was Fi bi , wi h a leas one model e alua ed
in 33 a icles, ollowed by he Apple Wa ch (n = 14), Ga min
(n = 12), Jawbone (n = 11) and Pola (n = 10). Simila o he
p e ious s a emen s o he INTERLIVE ne wo k, he da a
a e p esen ed in six key alida ion p o ocol and epo ing
domains comp ising o he a ge popula ion, c i e ion meas-
u e, index measu e, es ing condi ions, da a p ocessing and
s a is ical analysis (Fig.2). Wi hin each domain, aspec s
deemed c i ical o e ec i e alida ion and epo ing we e
iden i ied and a e ou lined wi h espec o he in o ma ion
colla ed du ing he s a emen p ocess.
3.1 Ta ge Popula ion
In he measu emen o TEE, a numbe o a iables con-
ibu e o indi idual a ia ion in de e mining bo h es ing
me abolic a e (RMR) and AEE, including age, sex, body
size and composi ion, e hnici y, gene ics and i ness le el
[6, 13]. Consume wea ables a e ma ke ed o a b oad global
demog aphic, om adolescen s o olde adul s as well as
om a hle es o hose wi h seden a y li es. Thus, unless
in es iga ing a speci ic clinical applica ion, alida ion s ud-
ies o EE es ima ion should e lec he he e ogenous na u e
o he a ge popula ion in he sample, and no be con ined
o a niche sec o . Twen y-se en (44%) o he s udies iden i-
ied in he sys ema ic li e a u e e iew ec ui ed hei sample
om a uni e si y communi y. While his may be con eni-
en , we ecommend ha i he aim o he s udy is alida-
ion o he wea able in he gene al popula ion, hen a mo e
he e ogenous sample is equi ed wi h a wide a ia ion in
EE es ima es. No ably, 13 o he 62 s udies (21%) ailed o
p o ide any epo o whe e he pa icipan s we e sampled
om, and 34 s udies (55%) did no epo how pa icipan s
we e ec ui ed. This in o ma ion should be a p e equisi e in
he epo ing o any alida ion s udy.
RMR is well documen ed o decline wi h age [22–24],
and while age is ac o ed in o many EE es ima ion equa-
ions [13], pa icipan s in alida ion s udies should ep esen
a spec um o ages, wi h due conside a ion o s a i ica-
ion acco ding o age anges. The cu en li e a u e ends o
alida e wea ables in he younge adul popula ion, wi h 35
s udies epo ing a sample wi h an a e age age in he 20s.
Fig. 1 PRISMA lowcha o
he sys ema ic e iew p ocess.
PRISMA P e e ed Repo ing
I ems o Sys ema ic Re iews
and Me a-Analyses

De e mining Validi y o Wea ables o Es ima ion o Ene gy Expendi u e
Olde adul s (> 60yea s) a e pa icula ly poo ly ep esen ed.
Alongside a ep esen a i e age g oup, i is impo an ha
alida ion p o ocols include an equal sample ac oss bo h
sexes, gi en he a iance in me abolic a e [6, 25], and epo
on body size and composi ion. Finally, skin one has p e i-
ously been no ed as ha ing an e ec on he accu acy o hea
a e measu es [17]. Gi en ha many consume wea ables
use hea a e in hei EE es ima ion algo i hm, i he de ice
includes pho ople hysmog aphy, skin one should also be
epo ed using he Fi zpa ick scale [26].
The a e age sample size ac oss all he s udies in he sys-
ema ic e iew was 34 pa icipan s ( ange 12–100), wi h
only nine a icles (15%) conduc ing a sample size calcula-
ion and jus i ica ion. Despi e he lack o sample size calcu-
la ions, many s udies conduc ed equi alence o di e ence
es s, which a e dependen on sample size. The e o e, i he
objec i e o he s udy was o de e mine a minimum accep -
able le el o accu acy, a sample size calcula ion should be
conduc ed based on pilo es ing o p e iously published
mean and s anda d de ia ion o he di e ences be ween he
index and c i e ion measu es [27]. I his is no he p ima y
ocus, o homogenous samples we ecommend a minimum
o 45 pa icipan s [28], al hough conside a ion should be
gi en o he pa icipan cha ac e is ics, and a la ge sample
size will likely be equi ed o mo e he e ogenous g oups.
3.2 C i e ion Measu e
I is widely ega ded ha he gold-s anda d app oach
o measu ing TEE is by using DLW [6, 7, 29, 30]. This
is assessed o e a pe iod o se e al days in a ee-li ing
con ex , and a e age daily TEE can be calcula ed o e a
speci ied ime pe iod ia he collec ion o u ine samples.
In o de o de e mine AEE, RMR is calcula ed ia indi ec
calo ime y o p edic ion equa ions and hen sub ac ed om
he TEE measu ed wi h DLW [31]. Howe e , i is no pos-
sible o measu e ac i i y ype, in ensi y o du a ion wi hin
he TEE o each ime pe iod [32], and his in o ma ion may
be ele an o many use s and clinicians. Equally, he use o
DLW is expensi e and equi es in-dep h specialis analy ical
acili ies, which places a es ic ion on he easibili y o i s
deploymen in many s udies [30, 32]. The e o e, while he
use o DLW is ecommended in ee-li ing p o ocols, o he
measu es such as calo ime y a e needed o he calcula ion
o AEE in speci ic ac i i ies.
Calo ime y in ol es he measu emen o ei he he mal
change (di ec calo ime y) o he measu emen o gaseous
exchange (indi ec calo ime y), and can ake he o m o
whole- oom me abolic chambe s, en ila ed hoods, o a
acemask/mou hpiece [33–35]. Indi ec calo ime y is mos
commonly used o measu e EE in he labo a o y, as i is
highly easible o measu e oxygen consump ion and cal-
cula e ene gy cos , ye his is no p ac ical in a ee-li ing
Fig. 2 Six domains and co esponding a iables o in e es iden i ied as being o impo ance in he alida ion o consume wea able and sma -
phone es ima ion o EE. EE ene gy expendi u e
R.A gen e al.
con ex [6]. The esul s o a ecen sys ema ic e iew and
me a-analysis sugges ha he accu acy o esea ch-g ade
wea ables o es ima ing EE is no a a sa is ac o y le el
o hese de ices o be used in he alida ion o comme -
cial wea ables as a c i e ion measu e [11]. The e o e, based
on he cu en a ailable e idence, we ecommend ha he
c i e ion measu e o he alida ion o speci ic ac i i ies
o exe cise p o ocols be indi ec calo ime y, wi h DLW
used o ee-li ing s udies. All i e s udies in he sys em-
a ic li e a u e e iew alida ing consume wea ables in a
ee-li ing con ex u ilised he DLW me hod [10, 36–39],
while 3 (10%) o he 28 semi- ee-li ing p o ocols u ilised
a me abolic chambe [10, 37, 40]. The emaining s udies
wi h a semi- ee-li ing p o ocol (25) and all 52 labo a o y
p o ocols selec ed indi ec calo ime y in he o m o a po -
able sys em o me abolic ca . The c i e ion de ice should be
placed acco ding o manu ac u e ’s ins uc ions and epo ed
in he s udy w i e-up, alongside labo a o y-speci ic da a on
he quali y o he c i e ion measu e whe e possible (i.e. pe -
cen age coe icien o a ia ion [ eliabili y]), and any cali-
b a ion de ails. In he case o using DLW in ee-li ing p o-
ocols and epo ing on AEE, au ho s should p o ide a ull
accoun o assump ions and equa ions used [6], o example
whe he RMR is calcula ed ia indi ec calo ime y o by
equa ion. We would ecommend ha he bes -p ac ice o
measu ing RMR in a ee-li ing p o ocol is wi h indi ec
calo ime y, a he han es ima ed using equa ions; howe e ,
we ecognise his may no always be easible o esea che s,
and in hose cases, he exac equa ion used should be s a ed.
3.3 Index Measu e
In o de o ensu e he ecological alidi y o a s udy p o ocol,
he placemen o he wea able de ice mus be conside ed,
especially in s udies e alua ing mul iple de ices a he same
ime. All comme cial wea ables should be e alua ed wi h he
de ice placed acco ding o he manu ac u e ’s ins uc ions.
Ac i i y moni o s a e commonly wo n on he w is , al hough
in some cases may be a ached o he wais o he use [41].
Less used placemen s include he o so [42] and he shoes
[43]. Fi een s udies iden i ied in he sys ema ic e iew
e alua ed mul iple w is -wo n de ices on he same a m in
he p o ocol, wi h up o h ee de ices wo n on one a m. I
is unclea wha e ec his placemen migh ha e on he ou -
pu s o he de ice, and, a guably, while s ill placed on he
lowe o ea m, a leas one o he h ee de ices is no being
wo n acco ding o he manu ac u e ’s ins uc ions. The e is
a nega i e impac o he easibili y o s udies i esea che s
a e equi ed o only place one de ice on each w is du ing a
es ing p o ocol, he e o e we would ecommend ha whe e
possible, esea che s a oid placing mul iple de ices on he
same w is , wi h a maximum o wo w is -wo n de ices
being es ed on one a m simul aneously. In addi ion, when
using wo w is -wo n de ices on he same a m, we ecom-
mend ha he e should be a andom coun e balanced place-
men o he de ices be ween pa icipan s; howe e , he o de
o de ice placemen wi h espec o dis ance om he w is
join should be clea ly epo ed.
Equally, sma phone applica ions may no ha e an explici
manu ac u e /de elope -speci ied placemen . O he ou
s udies in he sys ema ic e iew ha assessed sma phone
measu ed EE, one placed he sma phone a he lowe back
[44], one on he bel nex o a wea able a he mid-axilla y
line [45], one in a pocke (al hough he loca ion o he pocke
was no speci ied) [46], and he las s udy used wo sma -
phones, one in he hand and one in he igh pocke , wi h a
compa ison made be ween he wo posi ions [47]. I has been
epo ed ha in day- o-day li e, 60% o emales place hei
phone in hei bag, while 60% o males ca y hei s in hei
pocke [48]. As such, we would conside clo hing pocke s,
handbags o ca ying in he hand as he mos sui able posi-
ions o e alua e sma phone es ima ion o EE. The phone
should no be moun ed o he body in an unna u al way such
as o he ches o low back.
As well as epo ing he placemen p o ocol in de ail,
he exac model and e sion o he index de ice should be
clea ly speci ied, o bo h he ha dwa e and so wa e, includ-
ing no ing i any i mwa e upda es ook place du ing he
da a cap u e pe iod. Mos s udies epo ed he b and and
de ice name (e.g. Fi bi Cha ge HR); howe e , wi h egula
upda es o ha dwa e and so wa e, i is di icul o ully ep-
lica e he s udy wi hou speci ied e sion numbe s. Fu he -
mo e, he de ice should be ese back o baseline be ween
pa icipan s o ensu e he e is no in luence on de ice EE
algo i hms po en ially based on p e ious use. Finally, any
demog aphic and an h opome ic de ails inpu ed in o he
de ice, and he use o any speci ic exe cise modes, should be
epo ed. The use o exe cise modes has been highligh ed as
an a ea o u he examina ion, wi h esea che s and use s
cu en ly unawa e o he impac o using di e en modes on
he measu emen o EE [49, 50].
3.4 Tes ing Condi ions
Consume wea ables a e designed o p o ide a measu e o
EE in uncon olled en i onmen s such as daily EE, wi h
limi ed use in e ac ion wi h he de ice, and du ing mo e
con olled se ings whe e EE is es ima ed du ing a speci ic
exe cise/ac i i y. The esul s om he sys ema ic e iew
show ha many esea che s a e a ou ing he use o labo a-
o y o semi- ee-li ing p o ocols. O he 62 s udies included
in he sys ema ic e iew, 51 (82%) included a labo a o y
p o ocol, 27 s udies (44%) conduc ed some o m o semi-
ee-li ing in es iga ion, and only i e s udies (8%) exam-
ined ee-li ing condi ions.
De e mining Validi y o Wea ables o Es ima ion o Ene gy Expendi u e
Labo a o y p o ocols seek o alida e he wea able in
measu ing EE du ing asks ha a e well con olled. The
accu acy can be examined ac oss a ying in ensi ies and
include a combina ion o p ede ined walking, unning, and
cycling ac i i ies. The s udies iden i ied in he sys ema ic li -
e a u e sea ch wi h labo a o y p o ocols highligh ed a ying
le els o accu acy o a wea able in measu ing EE depend-
en on he in ensi y o he ac i i y. Addi ionally, in he case
o walking and unning, he accu acy o he index measu e
a ied dependen on he le el o incline o he ac i i ies in a
numbe o s udies [42, 51–53]. In con as , semi- ee-li ing
e alua ion inco po a es simula ed ac i i ies o daily li ing
and ac i i ies emula ing spo s o exe cises ha a e mo e
speci ic han walking, unning o cycling. Wi hin hese p o-
ocols, pa icipan s a e encou aged o comple e he asks as
hey would do du ing no mal daily li e, a a sel -selec ed
pace. The pu pose o hese ype o alida ion s udies is o
cap u e (1) speci ic spo s o complex ac i i ies, and/o (2)
a di e se ange o ac i i ies emula ing ac i i ies o daily li -
ing, such as elaxa ion, housekeeping, o o he physically
ac i e leisu e pu sui s. We a gue ha he accu a e measu e-
men o TEE and AEE du ing speci ic spo s o complex
ac i i ies is impo an because i allows end use s o de e -
mine he alidi y o hei de ice du ing ac i i ies o pa icu-
la ele ance o hem. Howe e , because o he cons ain s
o labo a o y equipmen and he labo a o y se ing, many
ac i i ies/spo s, and pa icula ly ac i i ies o daily li ing,
canno be pe o med in a manne ha is compa able o he
way hese ac i i ies o exe cise modes a e pe o med on a
daily basis. I his is no possible, we a gue ha he in o -
ma ion acqui ed om he ypical semi- ee-li ing s udy has
e y li le alidi y in de e mining he p ecision o EE om
consume de ices du ing ac ual ee-li ing beha iou s o
use s. In con as o ou p e ious ecommenda ions on he
alida ion o consume wea ables o measu e hea and s ep
coun [17, 18], we ecommend ha alida ion o TEE and
AEE om wea ables should be pe o med wi hin wo es ing
condi ions: (1) du ing speci ic ac i i ies o exe cises/spo s,
and (2) in a ee-li ing con ex .
In o de o accu a ely assess EE du ing a speci ic exe cise
o ac i i y, a dis inc ion be ween s eady s a e and a iable
in ensi y ac i i ies mus be made. Du ing s eady-s a e ac i i-
ies, s eady s a e mus be achie ed whe e hea a e emains
s able du ing a con inuous ask and ca diac ou pu is a a
su icien le el o suppo oxygen anspo in o de o mee
ene gy cos [54–56], be o e measu emen s a e included in
he analysis. The e is some deba e in he li e a u e abou
when s eady s a e is achie ed, bu he gene al consensus
is ha he e is a 2- o 5-min pe iod whe e VO2 and VCO2
a ies by up o 15% om he EE o he pe o med wo k,
depending on he ac i i y and he change in in ensi y g adi-
en [55–59]. The e o e, we ecommend alida ion o s eady-
s a e ac i i ies be pe o med ac oss di e en in ensi ies o
de e mine alidi y a di e en absolu e le els, wi h esea ch-
e s p o iding jus i ica ion o he achie emen o s eady s a e.
As a gene al ule o humb, bu dependen on he in ensi y
g adien and he absolu e in ensi y pe o med, each o he
ac i i ies/in ensi ies wi hin an exe cise/ac i i y-speci ic
p o ocol is ecommended o las a leas 6min o acili a e
s able s eady-s a e measu emen s. We ecommend conduc -
ing e alua ion wi h as wide a ange o in ensi ies as easible
and a conside a ion o he ele ance o g aded ac i i ies (e.g.
an incline ≥ 5% du ing walking o unning asks). Equally,
i conduc ing walking/ unning assessmen on a eadmill,
we would ecommend all es ing is conduc ed wi h a 1%
incline o accoun o he educed me abolic cos o eadmill
p opulsion [60]. Due conside a ion should be gi en o he
po en ial need o a eco e y pe iod be ween ac i i y bou s
when highe -in ensi y exe cises a e examined o allow su -
icien eco e y o app oxima ely RMR. The choice o all
in ensi ies should ake in o conside a ion he cha ac e is-
ics o he sample, wi h calcula ed in ensi ies based on he
pa icipan ’s maximal hea a e o VO2max being he mos
p e e able o e selec ing absolu e alues, o lesse s ill,
sel -selec ed in ensi ies. Howe e , while hese pe sonalised
in ensi ies a e ecommended, he e may be cases whe e i is
no easible o calcula e pe sonalised i ness le els, and, in
hese ins ances, conduc ing and epo ing absolu e exe cise
in ensi ies such as speed o wa s is ecommended.
Du ing hese ac i i ies, conside a ion o a ailable wo k-
ou modes on de ices a e needed as he mode selec ed
dic a es wha senso s a e enabled on he de ice in o de o
p ese e ba e y, o example indoo ac i i ies disable he
GPS and cycling does no equi e s ep de ec ion, and hese
modi ica ions a e likely o impac he alidi y o he meas-
u emen s. These use -de ined ac i i ies o assessmen o
EE end o ela e o he mos common wo kou s, including,
bu no limi ed o, unning, walking, cycling and swimming.
A emp ing o alida e de ices in o he asks ha a e no
de ined by he manu ac u e , such as eading, acuuming o
sweeping, is mos app op ia ely assessed in he alidi y o
TEE es ima ion in he ee-li ing en i onmen . Addi ionally,
a u he issue ha mus be add essed is he need o co -
ec o inaccu acies in he measu emen o EE a hea y o
maximal in ensi y ac i i y, whe e he anae obic componen
will no be cap u ed by indi ec calo ime y. Resea che s
conduc ing high-in ensi y ac i i ies should ecognise his,
adjus o i using an app op ia e me hod such as inco po-
a ing blood lac a e measu emen s [61, 62] o in e pola ion
based on exe cise in ensi y [63], and epo hese me hods
app op ia ely.
To assess EE es ima ion o consume wea ables in he
eal-wo ld, ee-li ing p o ocols should cap u e a ange
o ac i i ies om pa icipan s in uncon olled condi ions.
Gi en he ecommenda ion o he use o DLW in ee-li ing
alida ion, he p o ocol pe iod should las 7–14days, and
R.A gen e al.
pa icipan s should no be cons ained in hei ac i i ies in
any way [30, 64]. The epo ing o such p o ocols should
include in de ail he ins uc ions gi en o pa icipan s,
including whe he hey we e asked o use o did use any
speci ic exe cise modes on he wea ables du ing he pe iod.
Finally, i is p e e able o eco d and epo on he adhe ence
o pa icipan s o wea ing he de ice as ins uc ed o high-
ligh any disc epancies be ween de ices due o non-adhe -
ence, and epo on any missing da a. In he case o speci ic
ac i i y EE es ima ion, i is ecommended ha da a mus
be cap u ed wi h he pa icipan wea ing he de ice o he
en i e y o he p o ocol, and i he e is non-adhe ence o his
o he e a e missing da a, hen ha da a cap u e be disca ded.
Fu he mo e, o ee-li ing e alua ions, any me hods used
o in e pola e missing da a, such as du ing cha ging o e -
nigh , should be epo ed clea ly.
3.5 P ocessing
The da a p ocessing and epo ing ha is p o ided in ali-
da ion s udies is impo an bu is o en o e looked, wi h
nume ous a icles in he sys ema ic e iew lea ing he eade
le o make assump ions on he p ocessing me hods o he
s udy. Au ho s mus p o ide clea de ail on how s eady-s a e
o anae obic EE (i ele an ) was managed in hei p o o-
col, and how he da a collec ion, including synch onisa ion,
was managed o cap u e he measu es o he c i e ion and
index de ice pe ac i i y. Gi en he 2- o 5-min pe iod ha is
equi ed o achie e s eady s a e, we would ecommend ha
he a e age o he las 3min o he exe cise p o ocols o
s eady-s a e exe cises o ac i i ies be used o calcula e EE.
The e is a iance in he epo ing o he ype o EE being
measu ed, wi h lack o cla i y in pape s ega ding whe he
he measu e is TEE o AEE, and in he uni s used, wi h
kilocalo ies pe minu e (kcals/min), kilocalo ies pe ac i -
i y (kcals/ac i i y) and me abolic equi alen s (METs) all
being desc ibed in he li e a u e. Recen li e a u e epo s
METminu es o be he uni o choice o EE alida ion [15],
ye while he ime-phased na u e o hese uni s a e desi able
o compa abili y, we do no eel ha he consume ma -
ke is cu en ly able o unde s and METminu es. Fu he -
mo e, mos consume de ices epo EE in kcals. As such
we ecommend ha he p e e ed me ic should be kcals pe
uni o ime (minu e/day). Fu he mo e, esea che s should
speci y which equa ion is used o de e mine EE om gas-
eous consump ion, epo all ela ed assump ions, and a e
clea in epo ing whe he he s udy assessed TEE o AEE.
Equally wi h ega d o he index measu e, as much in o -
ma ion as possible should be p o ided on he inpu s o he
EE calcula ion o he de ice. Repo ing ha a p op ie a y
algo i hm was used should be deemed as he minimum c i-
e ia, wi h a emp s made o no e any o he inpu s o ha
speci ic EE algo i hm, including hea a e, accele ome e
da a, use demog aphics and subjec i e epo ing such as
a e o pe cei ed exe ion. This is somewha challenging in
many cases, gi en he ‘black-box’ na u e o hese p op i-
e a y algo i hms ha manu ac u e s do no wish o di ulge.
Addi ionally, whe e possible, esea che s a e encou aged o
ollow open science p inciples in making aw da a a ailable
using app op ia e da a eposi o ies o acili a e combined
analyses in he u u e.
Finally, he managemen o synch onisa ion be ween
de ices is ano he po en ial sou ce o e o . The app oach
o his will a y depending on he s udy design and de ices
used. As such, esea che s mus be cognisan o da a syn-
ch onisa ion when designing he s udy, and he synch o-
nisa ion p ocess unde aken should be desc ibed in as
much de ail as possible in he epo o allow o adequa e
eplica ion.
3.6 S a is ical Analysis
When assessing he alidi y o an index de ice o a c i e ion
measu e, he le els o accu acy o he index de ice should
be calcula ed wi h ag eemen be ween he wo de ices [65,
66]. The Bland–Al man app oach o limi s o ag eemen has
become widely used in he cu en medical li e a u e [67],
including 38 s udies (61%) in he sys ema ic e iew con-
duc ing his app oach in he analysis. Howe e , he e was
la ge a iance in he s a is ical app oaches used, wi h many
s udies u ilising measu emen s o co ela ion (e.g. Pea -
son, Spea man) [n = 38, 61%], compa ison o means (e.g.
es ) [n = 22, 36%], and measu es o ela i e eliabili y
(e.g. in aclass co ela ion coe icien ) [n = 13, 21%]. These
app oaches ha e been highligh ed as inapp op ia e when
assessing ag eemen be ween a measu emen ool and he
e e ence s anda d in medical ins umen alida ion s udies
[65].
To comp ehensi ely assess he alidi y o he index
de ice in es ima ing EE, we ecommend he use o
Bland–Al man limi s o ag eemen analysis in combina-
ion wi h mean absolu e pe cen age e o (MAPE). The
Bland–Al man me hod p o ides a measu e o he ag ee-
men be ween he c i e ion and index de ice; esea che s
should s a e i he assump ions o alid limi s o ag eemen
analysis we e ul illed [67], and, in addi ion, should inco -
po a e leas -p oduc s eg ession o assess o p opo ional
o ixed bias, as desc ibed by Ludb ook [66]. The use o
MAPE allows o compa ison be ween de ices and es ing
condi ions and is he a e age o he absolu e e o o a ool.
I is commonly used in desc ibing he e o o a p edic-
ion [68], and 29 s udies (47%) included in ou sys ema ic
e iew used his app oach in hei analysis. The use o bo h
me hods and ela ed isualisa ions p o ides a comp ehen-
si e assessmen o he g oup- and indi idual-le el alidi y
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Au ho s and A ilia ions
RobA gen 1,2,3 · MeganHe he ing on‑Rau h4· JulieS ang5· JakobTa p5· F anciscoB.O ega6,7·
PabloMolina‑Ga cia6· Mo i zSchumann8,9· WilhelmBloch8· SulinCheng8,9,10· Ande sG øn ed11·
JanCh is ianB ønd11· Ul Ekelund5· LuisB.Sa dinha4· B ianCaul ield1,2
1 Insigh Cen e o Da a Analy ics, Uni e si y College
Dublin, Dublin, I eland
2 School o Public Heal h, Physio he apy andSpo Science,
Uni e si y College Dublin, Dublin, I eland
3 School o Pha macy andBiomolecula Sciences, Royal
College o Su geons inI eland, Dublin, I eland
4 Exe cise andHeal h Labo a o y, CIPER, Faculdade de
Mo icidade Humana, Uni e sidade de Lisboa, Lisbon,
Po ugal
5 Depa men o Spo Medicine, No wegian School o Spo
Sciences, Oslo, No way
6 PROFITH (PROmo ing FITness andHeal h Th ough
Physical Ac i i y) Resea ch G oup, Depa men o Physical
Educa ion andSpo s, Facul y o Spo Sciences, Uni e si y
o G anada, G anada, Spain
7 Depa men o Bioscience andNu i ion, Ka olinska
Ins i u e , Solna, Sweden
8 Ins i u e o Ca dio ascula Resea ch andSpo s Medicine,
Depa men o Molecula andCellula Spo s Medicine,
Ge man Spo Uni e si y, Cologne, Ge many
9 Exe cise T ansla ional Medicine Cen e, heKey
Labo a o y o Sys ems Biomedicine, Minis y o Educa ion,
andExe cise, Heal h andTechnology Cen e, Depa men
o Physical Educa ion, Shanghai Jiao Tong Uni e si y,
Shanghai, China
10 Facul y o Spo andHeal h Sciences, Uni e si y
o Jy äskylä, Jy äskylä, Finland
11 Depa men o Spo s Science andClinical Biomechanics,
Resea ch Uni o Exe cise Epidemiology, Cen e o Resea ch
inChildhood Heal h, Uni e si y o Sou he n Denma k,
OdenseM, Denma k