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Time to exhaustion at and above critical power in trained cyclists: The relationship between heavy and severe intensity domains

Abstract and Figures

Objectives. — The aim of this study was to determine the physiological responses and time to exhaustion, at critical power and 5% above, in trained cyclists. Equipments and methods. — Eleven male cyclists completed an incremental test, three constant work rate tests to exhaustion to determine critical power (CP), and finally two tests until exhaustion at CP and CP plus 5%. Results. — The modeling of the power-inverse time relationship provided a mean critical power of 295 ± 39 W. Time to exhaustion at critical power was significantly higher than 5% above (22.9 ± 7.5 min versus 13.3 ± 5.8 min). Oxygen uptake, pulmonary ventilation, and blood lactate obtained at the end of the CP plus 5% exhaustion trial were not significantly different from the maximal variables. However, the physiological end values during the CP test were significantly lower compared to the incremental test. Conclusions. — These data support the idea that CP in trained cyclists is the physiological index that estimates the boundary between heavy to severe exercise domains. Thus, when cyclists exercised at a power output 5% higher than CP, the VO2max was reached at the end of exercise.
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Please
cite
this
article
in
press
as:
de
Lucas
RD,
et
al.
Time
to
exhaustion
at
and
above
critical
power
in
trained
cyclists:
The
relationship
between
heavy
and
severe
intensity
domains.
Sci
sports
(2012),
http://dx.doi.org/10.1016/j.scispo.2012.04.004
ARTICLE IN PRESS
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SCISPO-2704;
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of
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6
Science
&
Sports
(2012)
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ORIGINAL
ARTICLE
Time
to
exhaustion
at
and
above
critical
power
in
trained
cyclists:
The
relationship
between
heavy
and
severe
intensity
domains
Temps
d’épuisement
à
la
puissance
critique
et
au-dessus
chez
des
cyclistes
entraînés
R.D.
de
Lucas, K.M.
de
Souza,
V.P.
Costa,
T.
Grossl,
L.G.A.
Guglielmo
Sports
Center,
Federal
University
of
Santa
Catarina,
Physical
Effort
Laboratory,
Florianópolis,
CEP:
88040-900
Florianópolis
(SC),
Brazil
Received
3
December
2011;
accepted
5
April
2012
KEYWORDS
Physiological
responses;
Cycling;
Physiological
domains
Summary
Objectives.
The
aim
of
this
study
was
to
determine
the
physiological
responses
and
time
to
exhaustion,
at
critical
power
and
5%
above,
in
trained
cyclists.
Equipments
and
methods.
Eleven
male
cyclists
completed
an
incremental
test,
three
constant
work
rate
tests
to
exhaustion
to
determine
critical
power
(CP),
and
finally
two
tests
until
exhaustion
at
CP
and
CP
plus
5%.
Results.
The
modeling
of
the
power-inverse
time
relationship
provided
a
mean
critical
power
of
295
±
39
W.
Time
to
exhaustion
at
critical
power
was
significantly
higher
than
5%
above
(22.9
±
7.5
min
versus
13.3
±
5.8
min).
Oxygen
uptake,
pulmonary
ventilation,
and
blood
lactate
obtained
at
the
end
of
the
CP
plus
5%
exhaustion
trial
were
not
significantly
different
from
the
maximal
variables.
However,
the
physiological
end
values
during
the
CP
test
were
significantly
lower
compared
to
the
incremental
test.
Conclusions.
These
data
support
the
idea
that
CP
in
trained
cyclists
is
the
physiological
index
that
estimates
the
boundary
between
heavy
to
severe
exercise
domains.
Thus,
when
cyclists
exercised
at
a
power
output
5%
higher
than
CP,
the
VO2max was
reached
at
the
end
of
exercise.
©
2012
Elsevier
Masson
SAS.
All
rights
reserved.
Corresponding
author.
E-mail
address:
kristophersouza@yahoo.com.br
(K.M.
de
Souza).
0765-1597/$
see
front
matter
©
2012
Elsevier
Masson
SAS.
All
rights
reserved.
http://dx.doi.org/10.1016/j.scispo.2012.04.004
Please
cite
this
article
in
press
as:
de
Lucas
RD,
et
al.
Time
to
exhaustion
at
and
above
critical
power
in
trained
cyclists:
The
relationship
between
heavy
and
severe
intensity
domains.
Sci
sports
(2012),
http://dx.doi.org/10.1016/j.scispo.2012.04.004
ARTICLE IN PRESS
+Model
SCISPO-2704;
No.
of
Pages
6
2
R.D.
de
Lucas
et
al.
MOTS
CLÉS
Réponse
physiologique
;
Cyclisme
;
Domaines
physiologiques
Résumé
Objectifs.
Le
but
de
cette
étude
est
de
déterminer
les
réponses
physiologiques
et
le
temps
d’épuisement,
à
la
puissance
critique
et
à
5
%
au-dessus
de
la
puissance
critique
pour
des
cyclistes
entraînés.
Équipement
et
méthode.
Onze
cyclistes
masculins
ont
complété
un
test
progressif,
trois
tests
à
charge
constante
jusqu’à
épuisement
pour
déterminer
les
puissances
critiques
et
enfin
deux
tests
jusqu’à
épuisement
à
la
puissance
critique
et
puissance
critique
plus
5
%.
Résultats.
La
modélisation
de
la
relation
entre
puissance
inverse
et
le
temps
a
fourni
une
puissance
critique
de
295
±
39
W.
Le
temps
jusqu’à
l’épuisement
à
la
puissance
critique
a
été
considérablement
plus
élevé
que
5
%
au-dessus
(22,9
±
7,5
min
versus
13,3
±
5,8
min).
La
consommation
d’oxygène,
la
ventilation
pulmonaire
et
le
lactate
sanguin
obtenu
à
la
fin
de
l’essai
de
l’épuisement
à
la
puissance
critique
+5
%
n’ont
pas
été
considérablement
différents
des
variables
maximales.
Néanmoins,
les
valeurs
physiologiques
finales
pendant
les
puissances
critiques
test
ont
été
considérablement
inférieures
comparativement
au
test
progressif.
Conclusions.
Les
informations
appuient
l’idée
que
la
puissance
critique
des
cyclistes
entraînés
est
l’index
physiologique
qu’estime
la
limite
entre
le
domaine
d’exercice
lourd
et
sévère.
Donc,
quand
les
cyclistes
sont
entraînés
à
une
puissance
5
%
plus
élevée
que
la
puissance
critique,
la
consommation
maximale
d’oxygène
a
été
atteinte
à
la
fin
de
l’exercice.
©
2012
Elsevier
Masson
SAS.
Tous
droits
réservés.
1.
Introduction
The
hyperbolic
relationship
between
work
rate
and
time
to
exhaustion
(TTE)
is
a
fundamental
property
of
exercise
performance
in
humans
[1—4]
and
rats
[5,6].
Monod
and
Scherrer
[1]
first
reported
this
hyperbolic
relationship
in
a
single
muscle
group,
and
this
relationship
was
subsequently
demonstrated
during
whole-body
exercise,
such
as
cycling
[2],
treadmill
running
[7],
swimming
[8],
and
rowing
[9].
The
work-rate
asymptote
of
this
hyperbolic
relationship
has
been
termed
critical
power
(CP),
whereas
curva-
ture
constant
(i.e.
the
total
amount
of
work
that
can
be
performed
above
the
CP)
has
been
termed
anaer-
obic
work
capacity
(AWC)
[1—4].
The
parameters
CP
and
AWC
can
also
be
derived
through
linear
regression
analysis
after
transformation
of
the
hyperbolic
relation-
ship
into
a
linear
formulation
by
plotting
total
work
done
during
the
series
of
exercise
tests
versus
TTE
[1]
or
by
plotting
power
output
versus
the
inverse
of
TTE
(P
versus
1/TTE)
[3,4,10].
Tw o
decades
ago,
some
studies
aimed
to
better
under-
stand
the
definition
of
CP
by
investigating
the
intensity
domains
at
which
maximal
oxygen
uptake
(VO2max)
can
be
attained
[3,4].
It
was
demonstrated
that
CP
represented
the
highest
intensity
that
is
sustainable
for
a
prolonged
duration
without
eliciting
VO2max,
that
is,
the
lower
bound-
ary
for
severe
exercise
[3,4,11].
Accordingly,
some
authors
observed
a
non-attainment
of
VO2max,
despite
an
oxygen
uptake
slow
component
(VO2SC)
during
exercise
performed
at
CP
[3,4,11—13].
However,
the
variability
of
methods
proposed
to
deter-
mine
CP
has
not
provided
the
boundary
for
the
heavy
to
severe
exercise
domain,
since
previous
studies
reported
a
variation
of
24%,
depending
on
the
CP
mathematical
model
[14—16].
In
a
recent
review,
Dekerle
et
al.
[17]
highlighted
that
linear
model
P
versus
1/TTE
represents
the
best
esti-
mation
of
the
CP
concept,
showing
greater
absolute
value
when
compared
to
other
2-parameter
models.
Therefore,
this
model
has
been
used
to
investigate
the
physiological
responses
during
CP
exercise
[3,4,12,15].
However,
few
studies
have
analyzed
both
physiological
responses
and
TTE
at
CP
and
above.
Poole
et
al.
[3]
hypoth-
esized
that
CP
represented
an
intensity
that
was
slightly
above
physiological
steady
state
and,
hence,
would
lead
to
VO2max.
However,
the
authors
found
this
not
to
be
the
case,
and
power
needed
to
be
increased
by
approximately
16
W
(an
average
of
7%
of
CP)
to
elicit
VO2max in
a
group
of
active
subjects
[3].
A
subsequent
study
using
trained
cyclists
inves-
tigated
TTE
at
CP
and
found
an
average
end
value
of
91%
of
VO2max [12].
To
the
best
of
our
knowledge,
no
study
has
verified
these
physiological
responses
above
CP
in
trained
individuals
with
the
aim
of
analyzing
the
lower
limit
of
the
severe
domain.
Since
in
trained
subjects
CP
occurs
at
a
work
rate
closer
to
maximal
aerobic
power
output
(Pmax)
[18],
we
hypothesized
that
these
subjects
could
reach
VO2max at
a
lower
percentage
above
CP
(i.e.
5%)
than
active
people.
Thus,
the
aim
of
this
study
was
to
determine
the
physiological
responses
and
TTE
at
CP
(P
versus
1/TTE)
and
5%
above
(CP+5%)
in
competitive
cyclists.
2.
Subjects
Eleven
competitive
male
cyclists
(mean
±
SD;
20
±
5
years;
71
±
12
kg;
179
±
7
cm)
participated
in
the
study.
The
cyclists
had
been
training
for
and
competing
in
endurance
cycling
races
on
a
regular
basis
for
a
minimum
of
4
years.
At
the
time
of
testing,
they
were
in
the
beginning
of
the
yearly
training
program
and
were
cycling
approximately
400—450
km/wk.
After
being
fully
informed
of
the
risks
and
stresses
associ-
ated
with
the
study,
subjects
gave
their
written
informed
consent
to
participate.
The
study
was
performed
accord-
ing
to
the
Declaration
of
Helsinki,
and
the
protocol
was
approved
by
the
Ethics
Committee
of
the
Federal
University
of
Santa
Catarina,
Florianópolis,
Brazil.
Please
cite
this
article
in
press
as:
de
Lucas
RD,
et
al.
Time
to
exhaustion
at
and
above
critical
power
in
trained
cyclists:
The
relationship
between
heavy
and
severe
intensity
domains.
Sci
sports
(2012),
http://dx.doi.org/10.1016/j.scispo.2012.04.004
ARTICLE IN PRESS
+Model
SCISPO-2704;
No.
of
Pages
6
Time
to
exhaustion
at
and
above
critical
power
3
3.
Experimental
Protocol
Subjects
were
instructed
to
avoid
any
intake
of
caffeine
or
alcohol
and
strenuous
exercise
in
24
h
preceding
a
test
session
and
to
arrive
at
the
laboratory
in
a
rested
and
fully
hydrated
state,
at
least
3
h
postprandial.
All
tests
were
performed
at
the
same
time
of
day
in
a
controlled
envi-
ronmental
laboratory
condition
(19—22 C;
50—60%
RH)
to
minimize
the
effects
of
diurnal
biological
variation
on
the
results
[19].
Athletes
reported
to
the
laboratory
to
perform:
an
incremental
continuous
cycling
test
for
the
measure-
ment
of
VO2max and
Pmax;
three
constant
work
rate
tests
in
random
order
to
deter-
mine
TTE
at
95,
100,
and
110%
Pmax to
calculate
CP
using
the
linear
model
P
versus
1/TTE
[3];
two
sessions
to
determine
TTE
at
CP
and
CP+5%.
Subjects
performed
only
one
test
on
any
given
day,
and
the
tests
were
each
separated
by
24—48
h
but
completed
within
a
period
of
two
weeks.
3.1.
Procedures
3.1.1.
Materials
All
exercise
testing
was
performed
on
the
cyclist’s
own
bicy-
cle,
which
was
mounted
on
the
ComputrainerTM ergometer
system
(ComputrainerTM Pro
3D,
RacerMate,
Seattle,
Wash-
ington,
USA).
The
rear
wheel
was
inflated
to
800
kPa
after
which
the
system’s
load
generator
was
calibrated
to
a
rolling
resistance
between
0.88
and
0.93
kg.
This
calibration
proce-
dure
was
done
before
and
directly
after
the
15-min
warm-up
to
ensure
accurate
calibration
as
recommended
by
Davidson
et
al.
[20].
Respiratory
and
pulmonary
gas
exchange
varia-
bles
were
measured
breath-by-breath
during
all
protocols
(Quark
PFTergo,
Cosmed,
Rome,
Italy).
Before
each
test,
the
O2and
CO2analysis
systems
were
calibrated
using
ambient
air
and
a
gas
of
known
O2and
CO2concentration
according
to
the
manufacturer’s
instructions,
while
the
Quark
PFTergo
turbine
flow-meter
was
calibrated
using
a
3-L
syringe
(Cali-
bration
Syringe
3-L,
Cosmed,
Rome,
Italy).
Heart
rate
(HR)
was
continuously
recorded
during
the
tests
by
a
HR
monitor
incorporated
into
the
gas
analyzer.
Breath-by-breath
oxygen
uptake
(VO2)
and
HR
data
were
reduced
to
15
s
stationary
averages
throughout
the
tests
(Data
Management
Software,
Cosmed,
Rome,
Italy).
Capillary
blood
samples
(25
l)
were
obtained
from
the
ear
lobe
of
each
subject
during
all
tests,
and
the
blood
lactate
concentration
([lac])
was
measured
using
an
electrochemical
analyzer
(YSL
2700
STAT,
Yellow
Springs,
Ohio,
USA).
The
analyzer
was
calibrated
in
accor-
dance
with
the
manufacturer’s
recommended
procedures.
3.1.2.
Incremental
exercise
testing
The
incremental
test
started
at
100
W
and
was
continuously
increased
by
30
W
every
3
min
until
volitional
exhaustion
[21].
Blood
samples
were
collected
during
the
final
15
s
of
every
3
min.
Each
cyclist
was
verbally
encouraged
to
under-
take
maximum
effort.
VO2max was
considered
as
the
highest
value
obtained
in
a
15
s
interval.
The
attainment
of
VO2max
was
defined
using
the
criteria
proposed
by
Lacour
et
al.
[22].
Pmax was
determined
according
to
the
equation
Pmax
(W)
=
power
output
last
stage
completed
(W)
+
[t
(s)/step
duration
(s)
×
step
increment
(W)],
where
‘‘t’’
is
the
time
of
the
uncompleted
stage
[23].
3.1.3.
Determination
of
critical
power
The
CP
was
determined
using
three
TTE
values
measured
from
the
constant
work
rate
tests
(95,
100,
and
110%
Pmax).
Before
each
test,
subjects
completed
a
10-min
warm-up
at
50%
Pmax followed
by
a
5-min
rest,
after
which
the
sub-
jects
were
instructed
to
perform
the
required
power
output
until
they
were
unable
to
maintain
the
fixed
power
out-
put.
All
exercise
testing
was
performed
at
the
cyclist’s
preferred
cadence.
Subjects
were
verbally
encouraged
to
undertake
maximum
effort
for
as
long
as
possible
through-
out
the
tests.
Cardiorespiratory
variables
were
measured
continuously
during
all
protocols.
TTE
was
measured
to
the
nearest
second.
The
linear
model
P
versus
1/TTE
was
used
to
determine
CP
[24]:
P
=
(AWC/TTE)
+
CP;
where
TTE
=
time
to
exhaustion;
AWC
=
anaerobic
work
capacity;
P
=
power
out-
put;
CP
=
critical
power.
3.1.4.
Time
to
exhaustion
at
critical
power
and
5%
above
critical
power
After
a
10-min
warm-up
at
power
output
50%
Pmax followed
by
a
5-min
rest,
subjects
were
instructed
to
perform
the
required
power
output
(CP
and
CP+5%)
to
exhaustion.
Car-
diorespiratory
variables
were
measured
continuously
during
tests.
Both
exercise
tests
were
stopped
when
the
cadence
fell
below
the
preferred
cadence
and/or
until
volitional
exhaustion.
Athletes
were
blinded
to
the
time
elapsed
on
testing
protocols.
Blood
samples
were
collected
in
the
5th
min
and
at
exhaustion
to
determine
[lac].
TTE
was
measured
to
the
nearest
second.
The
VO2SC was
computed
as
the
dif-
ference
between
VO2at
exhaustion
and
the
3rd
min
of
the
exercise
[15].
3.1.5.
Statistical
analysis
All
data
throughout
are
expressed
as
mean
±
SD.
The
Shapiro-Wilk
test
was
applied
to
ensure
a
Gaussian
distri-
bution
of
the
data.
One-way
repeated-measures
ANOVA
was
used
to
compare
the
maximal
physiological
variables
from
incremental
exercise
test
with
end
physiological
variables
from
the
TTE
tests
at
CP
and
5%
above.
Two-way
repeated-
measures
ANOVA
was
used
across
intensities
(CP
and
CP+5%)
and
relative
time
(25%,
50%,
75%,
and
100%).
In
case
of
a
non-significant
interaction,
only
the
main
effect
of
the
test
was
considered.
When
intensity-by-time
interactions
were
significant,
post
hoc
one-way
ANOVA
was
performed
on
the
relevant
data,
and
the
Bonferroni-adjusted
paired
t-
test
was
used
as
appropriate
to
identify
differences
between
responses
at
specific
time
points.
The
level
of
significance
was
set
at
P
<
0.05.
4.
Results
VO2max,
Pmax,
HRmax,
VEmax,
and
[lac]max values
were
68.8
±
5.6
ml/kg/min,
344
±
43
W,
196
±
7
bpm,
164.1
±
26.4
l/min,
and
12.2
±
1.9
mmol/l,
respectively.
TTE
at
95,
100,
and
110%
Pmax values
were
9.9
±
3.8,
6.8
±
2.7,
and
3.8
±
2.0
min,
respectively.
The
model-
ing
of
the
power-inverse
time
relationship
(adjusted
Please
cite
this
article
in
press
as:
de
Lucas
RD,
et
al.
Time
to
exhaustion
at
and
above
critical
power
in
trained
cyclists:
The
relationship
between
heavy
and
severe
intensity
domains.
Sci
sports
(2012),
http://dx.doi.org/10.1016/j.scispo.2012.04.004
ARTICLE IN PRESS
+Model
SCISPO-2704;
No.
of
Pages
6
4
R.D.
de
Lucas
et
al.
r2=
0.95
±
0.05)
provided
mean
CP
values
of
295
±
39
W
(SEE
=
7.5
±
4.2
W).
TTE
at
CP
(22.9
±
7.5
min)
was
signifi-
cantly
higher
(P
<
0.01)
than
TTE
at
CP+5% (13.3
±
5.8
min).
The
ranges
of
the
TTE
values
for
the
two
intensities
were
15.6—42.5
min
at
CP
and
10.3—30.1
min
at
CP+5%.
In
addition,
TTE
values
from
the
two
intensities
were
highly
correlated
(r
=
0.90,
P
<
0.05).
However,
no
other
variable
was
associated
with
TTE
at
CP
and
CP+5%.There
was
no
significant
difference
between
VO2(68.0
±
6.3
ml/kg/min),
VE
(155.8
±
26.6
l/min),
and
[lac]
(11.0
±
2.4
mmol/l)
obtained
at
the
end
of
CP+5% exhaustion
trial
compared
to
the
incremental
test.
However,
the
end
value
of
VO2
(64.8
±
5.7
ml/kg/min),
VE
(145.7
±
22.5
l/min),
and
[lac]
(9.5
±
2.1
mmol/l)
during
the
CP
test
was
significantly
lower
than
VO2max,
VEmax,
and
[lac]max,
respectively.
The
VO2at
exhaustion
averaged
94%
of
VO2max.
The
end
HR
values
at
CP
(190
±
8
bpm)
and
CP+5% (189
±
7
bpm)
were
significantly
lower
than
the
HRmax (P
<
0.01).
The
mean
physiological
responses
during
exercise
at
CP
and
CP+5% are
shown
in
Fig.
1.
Two-way
ANOVA
with
repeated
measures
across
intensity
and
relative
time
revealed
no
significant
intensity-by-time
interaction
for
any
dependent
variables
(VO2,
P
=
0.99;
VE,
P
=
0.97;
HR,
P
=
0.96).
How-
ever,
the
main
effect
showed
that
VO2increased
over
time
until
75%
of
TTE.
In
contrast,
VE
and
HR
increased
over
the
entire
duration
of
the
tests.
We
did
not
find
sig-
nificant
differences
in
the
VO2SC between
the
intensities
(247
±
82
ml/min
versus
222
±
106
ml/min
for
CP
and
CP+5%,
respectively).
5.
Discussion
The
aim
of
this
study
was
to
determine
the
physiological
responses
during
TTE
at
CP
and
CP+5% in
competitive
cyclists.
The
main
finding
was
that
when
subjects
were
exercising
at
intensities
slightly
above
CP
(i.e.
5%),
VO2max was
attained.
Few
studies
have
analyzed
physiological
responses
at
CP
and/or
above
in
trained
cyclists
[12,25,26].
The
mean
value
of
CP
observed
in
our
study
was
300
W,
unlike
classic
stud-
ies
by
Poole
et
al.
[3,4]
conducted
with
physically
active
subjects
(CP
=
200
W).
The
subjects
different
fitness
levels
could
change
the
percentage
above
CP
in
which
VO2max was
reached
and
hence
the
lower
boundary
of
severe
domain
[18].
In
a
recent
review,
Jones
et
al.
[27]
highlighted
that
CP
was
found
to
occur
at
80%
of
VO2max,
approximately
midway
between
the
gas
exchange
threshold
and
VO2max
(50%
).
In
contrast,
Caputo
and
Denadai
[18]
showed,
in
trained
cyclists
(CP
=
303
W),
that
the
upper
bound-
ary
of
the
heavy
intensity
domain
lies
at
approximately
75%
,
suggesting
that
aerobic
training
modifies
the
rela-
tionship
between
CP
and
the
difference
between
first
lactate
threshold
and
VO2max.
In
the
present
investigation,
we
found
an
average
of
65%
,
and
this
value
could
be
explained
by
the
fact
that
experimental
procedures
were
held
in
the
beginning
of
the
competitive
season.
Never-
theless,
the
athletes
had
at
least
4
years
of
training
on
a
regular
basis,
ensuring
a
good
development
of
aerobic
fitness.
To
our
knowledge,
this
is
the
first
study
in
trained
cyclists
(VO2max =
68.8
ml/kg/min)
that
has
analyzed
TTE
Figure
1
Cardiorespiratory
measures
(mean,
SD)
during
time
to
exhaustion
at
critical
power
(CP)
and
5%
above
(CP+5%).
VO2
(A);
HR
(B);
VE
(C);
different
letters
mean
significant
difference
over
time
(P
<
0.05).
and
VO2response
at
and
above
CP.
We
have
used
a
fixed
percentage
above
CP
(i.e.
5%)
instead
of
the
fixed
work
rate
used
by
others
[11,28],
i.e.
10
or
15
W
above
CP
to
measure
physiological
responses
in
untrained
sub-
jects.
The
studies
published
by
Poole
et
al.
[3,4]
have
been
misunderstood
by
others
[11,12,29]
since
the
percentage
Please
cite
this
article
in
press
as:
de
Lucas
RD,
et
al.
Time
to
exhaustion
at
and
above
critical
power
in
trained
cyclists:
The
relationship
between
heavy
and
severe
intensity
domains.
Sci
sports
(2012),
http://dx.doi.org/10.1016/j.scispo.2012.04.004
ARTICLE IN PRESS
+Model
SCISPO-2704;
No.
of
Pages
6
Time
to
exhaustion
at
and
above
critical
power
5
above
CP
cited
does
not
represent
the
actual
value.
In
fact,
Poole
et
al.
[3,4]
used
5%
of
peak
power
output
from
the
incremental
test
to
calibrate
the
intensity
above
CP.
Con-
sequently,
the
subjects
exercised
at
different
percentages
above
CP
(i.e.
6—8%),
values
slightly
different
than
those
aforementioned
authors
have
described
(i.e.
8—11%
above
CP)
about
studies
from
Poole
et
al.
[3,4].
It
is
important
to
note
that
the
imprecision
of
the
CP
estimate
would
influ-
ence
VO2and
[lac]
responses,
as
well
as
TTE.
These
facts
lead
us
to
choose
a
fixed
percentage
over
a
fixed
work-
load,
since
our
results
showed
an
average
SEE
of
2.5
±
1.4%
(7.5
±
4.2
W)
and
hence
ensured
that
subjects
cycled
just
above
CP.
When
exercise
was
performed
at
CP+5%,
the
TTE
decreased
approximately
40%
compared
with
TTE
at
CP.
However,
the
VO2at
the
end
of
exercise
was
significantly
different
from
the
CP
test
but
not
different
from
VO2max
(Fig.
1A).
The
HR
values
were
very
close
to
HRmax (97%),
and
VE
had
no
significant
differences
from
VEmax (Figs.
1B
and
C,
respectively).
Also,
the
end
[lac]
was
not
sub-
stantially
different
from
the
incremental
exercise
testing.
Brickley
et
al.
[12]
reported
that
the
VO2at
CP
averaged
91%
of
VO2max.
In
agreement
with
this
study,
the
VO2response
at
CP
indicated
a
progressive
increase
reaching
94%
of
VO2max
at
exhaustion.
Therefore,
the
data
from
our
study
support
the
suggestions
that
VO2max is
not
elicited
at
CP
and
that
the
intensity
of
exercise
needs
to
be
increased
by
about
5%
for
VO2max to
be
reached.
This
is
in
accordance
with
the
description
of
the
severe
domain
(>
CP),
in
which
both
VO2and
[lac]
do
not
stabi-
lize
but
rise
continuously
over
time
until
VO2max is
reached
and/or
fatigue
resulting
from
the
metabolic
acidosis
termi-
nates
exercise
[30].
The
short
tolerance
observed
during
exercise
above
CP
has
been
associated
with
the
gradual
depletion
of
AWC,
which
is
determined
by
the
limited
sup-
plies
of
energy
[2].
A
previous
study
performed
with
an
exercise
intensity
of
10%
above
CP
found
a
gradual
deple-
tion
of
phosphocreatine
and
pH
and
an
increase
in
inorganic
phosphate
[31].The
TTE
observed
at
CP
agreed
with
stud-
ies
on
trained
cyclists
that
indicate
the
overestimation
of
maximal
lactate
steady
state
[12,32—34].
Housh
et
al.
[35]
reported
that
TTE
at
CP
was
33.3
min
±
14.4
s.
Brickley
et
al.
[12]
found
that
TTE
ranges
from
20.1
min
to
40.4
min
during
CP
tests.
In
the
study
by
Brickley
et
al.
[12],
the
subjects
who
had
the
highest
VO2max and
the
highest
CP
reached
their
exhaustion
time
earlier
(r
=
0.78;
r
=
0.92
P
<
0.05,
respectively).
In
the
present
study,
we
failed
to
demonstrate
any
significant
correlation
between
TTE
and
VO2max,
Pmax or
CP.
The
identification
of
meaningful
markers
of
the
inten-
sity
at
which
exercise
is
performed
is
useful
for
training
programs
and
studies
designed
for
athletes.
However,
the
methods
used
to
determine
the
CP
may
demarcate
the
exer-
cise
intensity
domains
at
a
different
power
output.
Some
studies
have
reported
that
CP
estimates
differ
significantly
depending
upon
the
mathematical
model
used
to
determine
the
power-time
relationship
(data
can
vary
by
up
to
24%)
[14,36].
More
recently,
Bull
et
al.
[15]
found
in
runners
that
critical
velocity
estimates
from
the
five
models
varied
by
18%.
Therefore,
these
studies
support
the
idea
that
the
lin-
ear
model
used
in
our
study
is
acceptable
to
estimate
the
boundary
of
heavy
to
severe
exercise
domain.
Thus,
CP
could
be
an
important
and
practical
index
to
prescribe
interval
training
between
these
domains.
6.
Conclusion
The
data
from
our
study
support
the
idea
that
CP
deter-
mined
in
trained
cyclists
(CP
=
300
W)
is
the
physiological
index
that
estimates
the
boundary
between
heavy
to
severe
exercise
intensity
domains.
In
addition,
the
physiological
variables
did
not
reach
steady
state
during
the
CP
test
to
exhaustion,
but
the
VO2max was
not
elicited.
However,
when
cyclists
had
exercised
at
a
power
output
5%
higher
than
CP,
the
VO2max was
reached
at
the
end
of
exercise.
Disclosure
of
interest
The
authors
declare
that
they
have
no
conflicts
of
interest
concerning
this
article.
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Time
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... Furthermore, mathematical modeling of lactate kinetics suggests that a true equilibrium between maximal whole body lactate production and oxidation results in a gradually increasing blood lactate concentration (Beneke, 2003). Therefore, since the so-called critical power (CP) has been shown to lie within the intensity region which distinguishes steady state from non-steady state oxidative metabolism (Poole et al., 1988;de Lucas et al., 2013;Vanhatalo et al., 2016), an emerging consensus recognizes CP to more accurately represent a MMSS than the MLSS Galan-Rioja et al., 2020). ...
... Interestingly, there were no significant differences, apart from a trivial effect size, between CP and 20 MMP . However, previous research has shown that time-to-fatigue at CP equals ∼23 min in both untrained (Poole et al., 1988) and trained cyclists (de Lucas et al., 2013). Conversely, CP has been found to reside ∼20 W above MLSS intensity (Pringle and Jones, 2002) which indicates a clear difference between CP and MLSS Galan-Rioja et al., 2020). ...
... The most direct non-invasive method of physiological validation for wholebody exercise is to measureVO 2 uptake. Several studies have reported the occurrence of aVO 2 steady state corresponding to a work rate at, or slightly below CP, whereas non-steady statė VO 2 were observed slightly above CP (Poole et al., 1988;de Lucas et al., 2013;Murgatroyd et al., 2014;Vanhatalo et al., 2016). In each case, the limit of tolerance was reached markedly sooner at the work rate slightly above CP. ...
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To investigate the agreement between critical power (CP) and functional threshold power (FTP), 17 trained cyclists and triathletes (mean ± SD: age 31 ± 9 years, body mass 80 ± 10 kg, maximal aerobic power 350 ± 56 W, peak oxygen consumption 51 ± 10 mL·min-1·kg-1) performed a maximal incremental ramp test, a single-visit CP test and a 20-min time trial (TT) test in randomised order on three different days. CP was determined using a time-trial (TT) protocol of three durations (12, 7 and 3 min) interspersed by 30 min passive rest. FTP was calculated as 95% of 20-min mean power achieved during the TT. Differences between means were examined using magnitude-based inferences and a paired-samples t-test. Effect sizes are reported as Cohen’s d. Agreement between CP and FTP was assessed using the 95% limits of agreement (LoA) method and Pearson correlation coefficient. There was a 91.7 % probability that CP (256 ± 50 W) was higher than FTP (249 ± 44 W). Indeed, CP was significantly higher compared to FTP (P = 0.041) which was associated with a trivial effect size (d = 0.04). The mean bias between CP and FTP was 7 ± 13 W and LoA were -19 to 33 W. Even though strong correlations exist between CP and FTP (r = 0.969; P < 0.001), the chance of meaningful differences in terms of performance (1% smallest worthwhile change), were greater than 90%. With relatively large ranges for LoA between variables, these values generally should not be used interchangeably. Caution should consequently be exercised when choosing between FTP and CP for the purposes of performance analysis.
... For the past 3 decades, however, numerous studies have shown the assumptions underlying CP determination to be inaccurate, as derived CP intensities could typically not be maintained for sufficiently long durations of ~ 30 min or longer (e.g., de Lucas et al. 2013;Dekerle et al. 2003;Sawyer et al. 2014). Other studies have shown CP to markedly overestimate MLSS (Pringle et al. 2002;Dekerle et al. 2003;Caritá et al. 2009, Greco et al. 2012Mattioni Maturana et al. 2016), and CP's associated blood [La -] has repeatedly been shown to exceed maximal sustainable values (e.g., Jenkins and Quigley 1992;Keir et al. 2015;Nixon et al. 2021). ...
... The vast majority of studies investigating CP TTEs, found CP intensity to be too hard to sustain for MLSS-comparable durations. Thus, while MLSS exercise intensity can, by definition, be maintained for over 30 min and even up to ~ 1 h, observed endurance times for CP intensities have typically been found in the 15-25-min range (e.g., de Lucas et al. 2013;Dekerle et al. 2003;Sawyer et al. 2014). Notable exceptions of just under 30 min, are Vautier et al. 1995 andBrickley et al. 2002. ...
... When reported data permit, the non-linearity phenomenon can be demonstrated in nearly all other studies (Caritá et al. 2009;Clingeleffer et al. 1994;Dekerle et al. 2003;de Lucas et al. 2013;Dupont et al. 2002;Greco et al. 2012;Hinckson and Hopkins 2005;Housh et al. 1989;Housh et al. 1990;Jenkins et al. 1998;Karsten et al. 2015;Kirby et al. 2021;Kordi et al. 2021;Mattioni Maturana et al. 2016;Muniz-Pumares et al. 2019;Nixon et al. 2021;Pethick et al. 2020;Valenzuela et al. 2021;Vandewalle et al. 1997). Table 1 highlights the non-arbitrary nature of the phenomenon. ...
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The elegant concept of a hyperbolic relationship between power, velocity, or torque and time to exhaustion has rightfully captivated the imagination and inspired extensive research for over half a century. Theoretically, the relationship’s asymptote along the time axis (critical power, velocity, or torque) indicates the exercise intensity that could be maintained for extended durations, or the “heavy–severe exercise boundary”. Much more than a critical mass of the extensive accumulated evidence, however, has persistently shown the determined intensity of critical power and its variants as being too high to maintain for extended periods. The extensive scientific research devoted to the topic has almost exclusively centered around its relationships with various endurance parameters and performances, as well as the identification of procedural problems and how to mitigate them. The prevalent underlying premise has been that the observed discrepancies are mainly due to experimental ‘noise’ and procedural inconsistencies. Consequently, little or no effort has been directed at other perspectives such as trying to elucidate physiological reasons that possibly underly and account for those discrepancies. This review, therefore, will attempt to offer a new such perspective and point out the discrepancies’ likely root causes.
... L −1 from the 10th to the 30th min) and a 30-min time limit [13]. An arbitrary time limit to determine any submaximal anchor or index should be avoided as the time to fatigue at the maximal metabolic steady state varies considerably [13,37,[167][168][169]. Furthermore, a steady state for blood lactate can be achieved beyond 30 min for exercise intensities that might otherwise be concluded to be above the MLSS [170]. ...
... In the late 1980′s, the first study assessed the homeostatic responses at and above CP (+ 5% of CP) derived via the traditional method [35] and confirmed the validity of CP to establish the boundary between heavy and severe exercise. These results have since been confirmed or reproduced several times [11,25,36,56,168,205,226,227]. A recent study has strengthened the case for CP as the delineator between heavy and severe exercise. ...
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Prescribing the frequency, duration, or volume of training is simple as these factors can be altered by manipulating the number of exercise sessions per week, the duration of each session, or the total work performed in a given time frame (e.g., per week). However, prescribing exercise intensity is complex and controversy exists regarding the reliability and validity of the methods used to determine and prescribe intensity. This controversy arises from the absence of an agreed framework for assessing the construct validity of different methods used to determine exercise intensity. In this review, we have evaluated the construct validity of different methods for prescribing exercise intensity based on their ability to provoke homeostatic disturbances (e.g., changes in oxygen uptake kinetics and blood lactate) consistent with the moderate, heavy, and severe domains of exercise. Methods for prescribing exercise intensity include a percentage of anchor measurements, such as maximal oxygen uptake (\({\dot{\text{V}}\text{O}}_{{{\text{2max}}}}\)), peak oxygen uptake (\({\dot{\text{V}}\text{O}}_{{{\text{2peak}}}}\)), maximum heart rate (HRmax), and maximum work rate (i.e., power or velocity—\({\dot{\text{W}}}_{{\max}}\) or \({\dot{\text{V}}}_{{\max}}\), respectively), derived from a graded exercise test (GXT). However, despite their common use, it is apparent that prescribing exercise intensity based on a fixed percentage of these maximal anchors has little merit for eliciting distinct or domain-specific homeostatic perturbations. Some have advocated using submaximal anchors, including the ventilatory threshold (VT), the gas exchange threshold (GET), the respiratory compensation point (RCP), the first and second lactate threshold (LT1 and LT2), the maximal lactate steady state (MLSS), critical power (CP), and critical speed (CS). There is some evidence to support the validity of LT1, GET, and VT to delineate the moderate and heavy domains of exercise. However, there is little evidence to support the validity of most commonly used methods, with exception of CP and CS, to delineate the heavy and severe domains of exercise. As acute responses to exercise are not always predictive of chronic adaptations, training studies are required to verify whether different methods to prescribe exercise will affect adaptations to training. Better ways to prescribe exercise intensity should help sport scientists, researchers, clinicians, and coaches to design more effective training programs to achieve greater improvements in health and athletic performance.
... In this context, maximal lactate steady state (MLSS) and critical power (CP) have been the focus of an intense debate concerning the transition from heavy to severe domains (Garcia-Tabar & Gorostiaga, 2019;Jones, Burnley, Black, Poole, & Vanhatalo, 2019). Whereas MLSS represents the upper limit of blood lactate concentration (BLC) resulting in a lactate steady state during constant intensity (Beneke, 2003;Heck et al., 1985), CP represents the highest exercise intensity at which a steady state of oxygen consumption (V̇O 2 ) response is still attained (De Lucas, De Souza, Costa, Grossl, & Guglielmo, 2013;Poole, Ward, Gardner, & Whipp, 1988). Although these two markers have been previously suggested (Burnley & Jones, 2007;Faude et al., 2009;Poole et al., 1988) as the upper boundary of the heavy domain (i.e. ...
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The aim of this study was threefold: a) to compare the maximal lactate steady state (MLSS) with critical power (CP); b) to describe the relationship of MLSS with rowing performances; and c) to verify the agreement of MLSS with several exercise intensity thresholds in rowers. Fourteen male rowers (mean [SD]: age = 26 [13] years; height = 1.82 [0.05] m; body mass = 81.0 [7.6] kg) performed on a rowing ergometer: I) discontinuous incremental test with 3-min stages and 30-s recovery intervals (INC3min); II) continuous incremental test with 60-s stages (INC1min); III) two to four constant workload tests to determine MLSS; and IV) performance tests of 500-m, 1000-m, 2000-m and 6000-m to determine CP. Twenty-seven exercise intensity thresholds based on blood lactate, heart rate and ventilatory responses were determined by incremental tests, and then compared with MLSS. CP (257 [38] W) was higher than MLSS (187 [25] W; p < 0.001), with a very large mean difference (37%), large typical error of estimate (14%) and moderate correlation (r = 0.48). Despite the correlations between MLSS and most intensity thresholds (r > 0.70), all presented low correspondence (TEE >5%), with a lower bias found between MLSS and the first intensity thresholds (-12.5 to 4.1%). MLSS was correlated with mean power during 500-m (r = 0.65), 1000-m (r = 0.86) and 2000-m (r = 0.78). In conclusion, MLSS intensity is substantially lower than CP and presented low agreement with 27 incremental-derived thresholds, questioning their use to estimate MLSS during rowing ergometer exercise.
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To the Editor. As previously demonstrated by Iannetta et al. (1), a model considering intensity domains for exercise prescription and for describing physiological characteristics of individuals should be recommended. Recently, Podlogar et al. (5) suggested that the critical power (CP)/critical speed (CS), the power/speed at the boundary of the heavy and severe intensity domains, should be considered as the parameter that is capable of best predict performance across a wide range of intensities. However, CP/CS is not the only and exclusive parameter separating two intensity domains. Other parameters such as oxygen uptake kinetics, lactate and ventilatory thresholds, and maximum lactate steady-state can be used. In fact, high and very high correlations were obtained between CS and ventilatory threshold, respiratory compensation point, and maximal oxygen uptake (3). Moreover, although CP/CS concept is of interest, a significant effect of the mathematical models (3) and fitting procedures (4) used to estimate CS was observed. Therefore, coaches/researchers should i) choose a statistically appropriate fitting procedure to their specific dataset to define CS and corresponding intensity domains, and maintain it over the season (4); ii) physiologically verify the CS estimation during the season; and iii) use training prescription around CS (±10%) to take into account the confidence interval of its estimation and the day-to-day variability (3). On the other hand, using CP in running could be useful to prescribe training intensity when running speed is no longer a relevant metric to rely upon (e.g., when running on a variable terrain or in a very windy condition) (2).
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TO THE EDITOR: Podlogar et al. (1) have nicely discussed current methods for classifying athletes in applied physiology studies attending to their training or performance level. We agree with them that relying on a single physiological marker such as maximum oxygen uptake is not without limitations and endorse the use of more performance-based indicators. However, before proposing critical power/speed (CP/ CS) as the primary indicator of an athlete's training status, the robustness of these variables and the best method for their determination remains to be confirmed. Differences in mathematical models or test durations can indeed have a remarkable impact on an individual's CP/CS (e.g., up to $1 km/ h for CS in top-level runners) (2). More research is needed to provide reference or "norma-tive" values of CP/CS allowing classification of athletes into different performance/fitness categories. An alternative, at least in cycling, might be classifying athletes attending to the highest power output that they can achieve for a given duration the so-called "mean maximum power" (MMP) (3). This approach does not require the use of mathematical calculations or additional laboratory testing and is sensitive enough to allow discerning actual performance even between the two highest category levels-Union Cycliste Internationale [UCI] ProTeam versus UCI WorldTour-in professional cyclists (4). We have recently reported normative MMP values for male (n = 144) (4) and female professional cyclists (n = 44) (5). If a similar approach was used in cyclists of a lower training/com-petition level, scientists and coaches could accurately classify participants in cycling physiology studies. DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the authors. REFERENCES 1. Podlogar T, Leo P, Spragg J. Using V _ o 2max as a marker of training status in athletes-can we do better? J Appl Physiol (1985). TO THE EDITOR: We read with interest the Viewpoint by Podlogar et al. (1) proposing that critical power (CP, defined as power at the boundary of the heavy/severe-exercise intensity domains) rather than maximal oxygen uptake (V _ O 2max) should be used as the primary descriptor of participants' training status, and we offer the following comments: 1. Correct classification of athletes should be based only on performance criteria and not on any physiological factors that, either isolated or combined, can never encompass the complexity of the multiple components of endurance performance. 2. V _ O 2max remains a gold-standard criterion and there is no doubt that values above 85 mL/kg/min characterize world-class endurance athletes. However, limiting the classification of aerobic level of athletes to V _ O 2max is restrictive and the analysis of submaximal intensity factors should complement but not replace it. 3. We disagree with the statement that CP is the best (or least bad) of these submaximal factors. Important 148 8750-7587/22
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TO THE EDITOR: We appreciate the physiologically informed discussion presented in the Viewpoint by Podlogar et al. (1). However, it is well known that the determinants of endurance performance are the maximal oxygen uptake (V_ o2max), exercise economy (RE), and lactate threshold (LT) (2). The inclusion of the critical power/speed as proposed by the authors is a good alternative, although we consider that there is not enough data in the literature to compare between subjects. V_ O2max is strongly correlated with endurance performance in heterogeneous groups; however, this relationship is lower in homogeneous groups of endurance athletes. Thus, other factors such as fractional utilization of V_ O2max and exercise economy/efficiency (3) might help to explain the differences between athletes. We propose to establish a classificationaccording to the three main determinant factors mentioned above relative to the upper limit for each sport found in the literature or relative to V_ O2max/peak. For example, relative V_ O2max values 80 and 85mL·kg 1·min 1 for female and male distance runners, respectively, have been reported previously in the literature (4). Regarding the RE, the Ethiopian runner Zersenay Tadese has showed values of 150 mL O2·kg· 1·km 1 at 19 km·h 1 or the British female distance runner Paula Radcliffe has showed values of 44 mL·kg 1·min 1 at 19 km·h 1. Finally, high values of LT ( 83% of V_ O2peak) or lactate turn-point ( 92% of V_ O2peak) have been found in elite distance runners and critical speed (CS) occurring at 90% of V_ O2peak (5). Therefore, a male runner with 70 mL·kg 1·min 1 of V_ O2max, 200 mL O2·kg· 1 ·km 1 at 19 km·h–1, and lactate turn-point of 80% of V_ O2peak would represent an average 82% relative to the best distance runners.
Chapter
The present chapter is devoted to the experiential now as an individual fundamental entity of the complex present that plays the pivot role in dynamics of the human temporality. In our theory, the implementation cost of action strategies is determined by effort. For this reason, we elucidate its essential properties and develop the multi-component theory of subjective effort. Turning to the laws of psychophysics, we develop the description of subjective effort in terms of one-dimensional clouds in the space of effort magnitudes experienced by the subject. Two components of subjective effort are singled out. One is the experienced effort of bodily executed actions. The other is the mental effort related to monitoring the results of bodily actions. The available psychological and physiological data that enable us to develop the original mathematical description of subjective effort are presented. In particular, the power-law of memory load, the regularities of speed-accuracy tradeoff are used to construct the mental effort of monitoring which admits the interpretation as quasi-entropy of subject’s actions. To fuse the two types of subjective effort, we propose a new concept of an endless cloud cycle dealing with effort-as-experienced and effort-as-evaluated. This concept enables us to employ the notion of time-to-fatigue in order to make the two types of subjective effort mutually commensurable. As a result, a nonlinear model for the effort fusion is elaborated, which may be treated as an analogy to free energy. The appendix presents the details of the mathematical constructions and experimental data on binary categorization that underlie the mathematical description of subjective effort including the experienced effort of bodily executed actions and the mental effort of monitoring the results of bodily actions.
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There is a pervasive belief that the severe-intensity domain is defined as work rates above the power associated with a maximal lactate steady state (MLSS) and by a oxygen uptake (V̇O 2 ) response that demonstrates a rapid increase (primary phase) followed by a slower increase (slow component), which leads to maximal oxygen uptake (V̇O 2max ) if exercise is continued long enough. Fifteen university students performed 5 to 7 tests to calculate power at MLSS (154 ± 29 W). The tests included 30 min of exercise at each of 3 work rates: (i) below (–2 ± 1 W) power at MLSS, (ii) above (+4 ± 1 W) the power at MLSS, and (iii) well above (+19 ± 8 W) power at MLSS. The V̇O 2 response in each test was described using mathematical modeling. Contrary to expectation, the response at the supra-MLSS work rates had not 2, but 3, distinct phases: the primary phase and the slow component, plus a “delayed” third phase, which emerged after ∼15 min. V̇O 2max was not attained at supra-MLSS work rates. These results challenge commonly held beliefs about definitions and descriptions of exercise intensity domains. Novelty: The V̇O 2 response at work rates that are too high to sustain a lactate steady state but not high enough to elicit V̇O 2max features not 2, but 3, distinct phases. There is no consensus on whether intensity domains should be defined by their boundaries or by the responses they engender.
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Purpose: To validate and compare a novel model based on the critical power (CP) concept that describes the entire domain of maximal mean power (MMP) data from cyclists. Methods: An omni-domain power-duration (OmPD) model was derived whereby the rate of Wʹ expenditure is bound by maximum sprint power and the power at prolonged durations declines from CP log-linearly. The three-parameter CP (3CP) and exponential (Exp) models were likewise extended with the log-linear decay function (Om3CP and OmExp). Each model bounds Wʹ using a different nonconstant function, Wʹeff (effective Wʹ). Models were fit to MMP data from nine cyclists who also completed four time-trials (TTs). Results: The OmPD and Om3CP residuals (4 ± 1%) were smaller than the OmExp residuals (6 ± 2%; P < 0.001). Wʹeff predicted by the OmPD model was stable between 120–1,800 s, whereas it varied for the Om3CP and OmExp models. TT prediction errors were not different between models (7 ± 5%, 8 ± 5%, 7 ± 6%; P = 0.914). Conclusion: The OmPD offers similar or superior goodness-of-fit and better theoretical properties compared to the other models, such that it best extends the CP concept to short-sprint and prolonged-endurance performance.
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For high-intensity muscular exercise, the time-to-exhaustion (t) increases as a predictable and hyperbolic function of decreasing power (P) or velocity (V). This relationship is highly conserved across diverse species and different modes of exercise and is well described by two parameters: the 'critical power' (CP or CV), which is the asymptote for power or velocity, and the curvature constant (W') of the relationship such that t = W'/(P-CP). CP represents the highest rate of energy transduction (oxidative ATP production, V? O2) that can be sustained without continuously drawing on the energy store W' (composed in part of anaerobic energy sources and expressed in kilojoules). The limit of tolerance (time t) occurs when W' is depleted. The CP concept constitutes a practical framework in which to explore mechanisms of fatigue and help resolve crucial questions regarding the plasticity of exercise performance and muscular systems physiology. This brief review presents the practical and theoretical foundations for the CP concept, explores rigorous alternative mathematical approaches, and highlights exciting new evidence regarding its mechanistic bases and its broad applicability to human athletic performance.
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The aim of this study was to examine the response of physiological parameters during exercise to exhaustion at Critical Power (CP). Eight male trained subjects performed a test to exhaustion on a cycle ergometer at a constant power corresponding to their previously determined CP. Mean CP value was 283.6±20W and corresponded to 85.4±4.8% of VO2 max. Time to exhaustion was 22.1±10.1min and was associated with a pattern in lactate concentration, redox state, ammonia concentration, minute ventilation, respiratory rate, heart rate. Likewise, a decrease of [HCO3-], PaCO2 and base excess was observed between the 10th min and the end of the test, associated with an acidosis which cannot be compensated. The rise in these parameters could lead to exhaustion and the inability to maintain the exercise intensity. VO2 did not change after the 10th min of the test but was higher than the level expected for this intensity, due to a VO2 slow component though VO2 max level was not attained. These results demonstrated that CP does not correspond to a sustainable and physiological steady state intensity.
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Physiological variables, such as maximum work rate or maximal oxygen uptake (V̇O2max), together with other submaximal metabolic inflection points (e.g. the lactate threshold [LT], the onset of blood lactate accumulation and the pulmonary ventilation threshold [VT]), are regularly quantified by sports scientists during an incremental exercise test to exhaustion. These variables have been shown to correlate with endurance performance, have been used to prescribe exercise training loads and are useful to monitor adaptation to training. However, an incremental exercise test can be modified in terms of starting and subsequent work rates, increments and duration of each stage. At the same time, the analysis of the blood lactate/ventilatory response to incremental exercise may vary due to the medium of blood analysed and the treatment (or mathematical modelling) of data following the test to model the metabolic inflection points. Modification of the stage duration during an incremental exercise test may influence the submaximal and maximal physiological variables. In particular, the peak power output is reduced in incremental exercise tests that have stages of longer duration. Furthermore, the VT or LT may also occur at higher absolute exercise work rate in incremental tests comprising shorter stages. These effects may influence the relationship of the variables to endurance performance or potentially influence the sensitivity of these results to endurance training. A difference in maximum work rate with modification of incremental exercise test design may change the validity of using these results for predicting performance, and prescribing or monitoring training. Sports scientists and coaches should consider these factors when conducting incremental exercise testing for the purposes of performance diagnostics.
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O principal objetivo deste estudo foi comparar a intensidade correspondente à máxima fase estável de lactato (MLSS) e a potência crítica (PC) durante o ciclismo em indivíduos bem treinados. Seis ciclistas do sexo masculino (25,5 ± 4,4 anos, 68,8 ± 3,0kg, 173,0 ± 4,0cm) realizaram em diferentes dias os seguintes testes: exercício incremental até a exaustão para a determinação do pico de consumo de oxigênio (VO2pico) e sua respectiva intensidade (IVO2pico); cinco a sete testes de carga constante para a determinação da MLSS e da PC; e um exercício até a exaustão na PC. A MLSS foi considerada com a maior intensidade de exercício onde a concentração de lactato não aumentou mais do que 1mM entre o 10º e o 30º min de exercício. Os valores individuais de potência (95, 100 e 110% IVO2pico) e seu respectivo tempo máximo de exercício (Tlim) foram ajustados a partir do modelo hiperbólico de dois parâmetros para a determinação da PC. Embora altamente correlacionadas (r = 0,99; p = 0,0001), a PC (313,5 ± 32,3W) foi significantemente maior do que a MLLS (287,0 ± 37,8W) (p = 0,0002). A diferença percentual da PC em relação à MLSS foi de 9,5 ± 3,1%. No exercício realizado na PC, embora tenha existido componente lento do VO2 (CL = 400,8 ± 267,0 ml.min-1), o VO2pico não foi alcançado (91,1 ± 3,3 %). Com base nesses resultados pode-se concluir que a PC e a MLSS identificam diferentes intensidades de exercício, mesmo em atletas com elevada aptidão aeróbia. Entretanto, o percentual da diferença entre a MLLS e PC (9%) indica que relação entre esses dois índices pode depender da aptidão aeróbia. Durante o exercício realizado até a exaustão na PC, o CL que é desenvolvido não permite que o VO2pico seja alcançado.
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Background: The RacerMate Inc. CompuTrainer is an increasingly popular ergometer in Sport Science laboratories, yet there is little information on the characteristics and validity of the CompuTrainer calibration procedure. Aim: To investigate the effect of a range of environmental temperatures on the CompuTrainer calibration procedure and validate the power output against an SRM powermeter. Methods: A bicycle fitted with an SRM Training System was attached to a CompuTrainer ergometer. The calibration procedure was repeated (up to 5 occasions) interspaced with 2min cycling at 200W and ∼90rpm. The cyclist then cycled for a further 2min at 200W for a direct comparison with the SRM training system. This process was repeated at seven different random calibration values at a range of environmental temperatures (15, 20, 28 and 38°C). Results: At all temperatures there was a large decline in calibration pressure after the first 2min of cycling, with no further decline after 6min of cycling. This decline was inversely correlated with the temperature (r2 = 0.7). In low temperatures (15° and 20°C) the CompuTrainer significantly underestimated SRM power by 7.3 ± 5.8 W (95%CI: 4.2-10.4W; Range 1-18W; p = 0.0002) but was similar (-0.3 ± 4.4W) in high temperatures (28° and 38°C) (95%CI: -2.7-2.0W; Range -9-5W; p = 0.78). Conclusions: Both temperature and calibration procedure were shown to affect power measurement and thus these authors have suggested an alternative procedure to enhance the reliability and validity of the CompuTrainer ergometer.
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