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Incremental exercise test design and analysis: implications for performance diagnostics in endurance athletes


Abstract and Figures

Physiological variables, such as maximum work rate or maximal oxygen uptake (VO2max), 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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Sports Med 2007; 37 (7): 575-586
© 2007 Adis Data Information BV. All rights reserved.
Incremental Exercise Test Design
and Analysis
Implications for Performance Diagnostics in
Endurance Athletes
David J. Bentley,
John Newell
and David Bishop
1 School of Medical Sciences, Health and Exercise Science, The University of New South Wales,
Sydney, New South Wales, Australia
2 Department of Mathematics, National University of Ireland, Galway, Ireland
3 Facolt
a di Scienze Motorie, Universit
a degli Studi di Verona, Verona, Italy
Physiological variables, such as maximum work rate or maximal oxygen
uptake (
), 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 scien-
tists 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 submax-
imal and maximal physiological variables. In particular, the peak power output is
reduced in incremental exercise tests that have stages of longer duration. Further-
more, 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 con-
ducting incremental exercise testing for the purposes of performance diagnostics.
There are a number of biomechanical, environ- durance task) and ‘performance oxygen uptake’
mental, nutritional and psychological factors that
), which is, in turn, influenced by the percent-
will potentially influence endurance perform-
age of
at the lactate threshold (LT), as well as
However, it is generally regarded that ‘per-
the maximum oxygen uptake (
formance velocity’ (the average speed in an endur-
important physiological characteristics are usually
ance event) will be dictated by the ‘performance
power’ (the average work performed during an en- determined from incremental exercise testing and
576 Bentley et al.
are considered to be necessary for athletes to suc- athletes have suggested that
does not neces-
cessfully perform in endurance events.
sarily distinguish performance in a variety of endur-
ance events.
At the same time, the relationship
Incremental exercise testing is a standard proce-
and endurance performance could
dure for determining submaximal and maximal
be a function of the duration and intensity of the
physiological variables such as
and the LT.
endurance task with shorter duration, higher intensi-
However, a key variant in most scientific research
ty tasks better correlated with performance.
and performance diagnosis is the type of incremen-
more practical significance, the use of
tal test that is used. An incremental protocol can be
prescribe training is very limited, as athletes rarely
modified on the basis of the starting work rate, as
monitor exercise intensity using
well as the duration and magnitude of work rate
ments. Furthermore, it has been commonly observed
increments. Currently, there is no consensus on the
in well trained endurance athletes that
methods used to measure submaximal physiological
ies little with short to moderate term training inter-
parameters from such tests. The purpose of this
Hence, while it is important to quanti-
article is to present a contemporary literature review
, it is a variable that may not be that useful
concerning the effects of modifying an incremental
in terms of prescribing or monitoring training effects
exercise protocol on maximal and submaximal
in well trained endurance athletes. Therefore, other
physiological variables related to endurance per-
maximal or submaximal physiological variables
formance. Studies examining the methodological
should also be quantified in conjunction with
factors influencing the physiological parameters as-
for the purpose of predicting performance
sociated with endurance performance will be re-
and designing endurance training programmes.
viewed. This article focuses specifically on trained
endurance athletes.
1.1.2 Maximum Work Rate
1. Performance Diagnostics
The maximum work rate obtained during an in-
cremental exercise test has also become popular as a
An aim of sport science research and practice has
marker of endurance performance in running and
been to quantify the relationship between maximal
Individualised interval training can
and submaximal physiological variables and endur-
also be prescribed for cyclists on the basis of peak
ance performance.
At the same time, maximal
power output (PPO).
In line with this, PPO has
and submaximal physiological variables can be used
also been used to monitor the effects of endurance
to prescribe endurance training or to monitor the
training in elite cyclists.
If portable devices are
effects of training.
The validity of these physio-
available to measure power output during cycling in
logical variables, in terms of performance diagnos-
the field, PPO can be used to determine the intensity
tics, are numerous and their interrelationship with
of exercise in cycling.
Of practical significance,
each other has not been well defined due to their
the PPO has been shown to correlate (r = 0.97) with
definitions, incremental exercise protocol design
Therefore, this variable can be used to
and procedures.
without equipment for respiratory
exchange analysis. Hence, the maximum work rate
1.1 Definitions and Use of Maximal and
obtained from an incremental exercise test to ex-
Submaximal Physiological Variables
haustion is a physiological variable that can be used
for a variety of purposes in sport science testing.
1.1.1 Maximal Aerobic Power
Administering an increase in work rate during There are a variety of terms used to describe the
incremental exercise has long been used as a method maximum work rate including ‘peak power output’
to induce a peak or plateau in
(i.e. or ‘maximum work rate’ in cycling, or ‘peak tread-
Significant correlations between mill velocity’ in running.
The former definition
and distance running, cycling and triathlon should not be confused with the PPO obtained dur-
performance have been observed in athletes of mix- ing short ‘all-out’ tests of anaerobic power.
ed ability.
However, investigations in elite maximum work rate is obtained by measuring the
© 2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (7)
Exercise Test Design and Analysis 577
highest, fully completed stage for a pre-determined see Brooks,
Loat and Rhodes,
and Svedahl and
period during an incremental test.
This ranges MacIntosh
). For example, some authors consider
from 60 seconds to 4 minutes in duration.
If a a LT to occur at a work intensity preceding the first
single work stage is not completed, equations can be increase in lactate concentration above the resting
used to establish the maximum work rate that con- level.
Others have suggested a LT to occur at the
siders the fraction of the completed stage where preceding of the first increase in lactate concentra-
fatigue occurred.
Therefore, peak work rate is a tion of 1 mmol/L.
To overcome the disadvantages
function of the incremental exercise test design, the of visual, subjective determination of LTs, impor-
implications of which are not well defined. tant changes in lactate concentration may also be
identified by using logarithmic transformations
The reliability (coefficient of variation = 2%) of
and various curve-fitting procedures, such as the
PPO obtained from an incremental test comprising
DMax method, which is also thought to correspond
of short (60-second stages) has been shown to be
with the so-called ‘lactate steady state’ during incre-
However, this study is the only one of its
mental exercise.
Other researchers have proposed
kind. Indeed, within the literature, the differences in
that a fixed blood lactate concentration (FBLC),
incremental test protocol are large and this may
such as 2 mmol/L or 4 mmol/L, the so-called ‘onset
impact on the maximal (and submaximal) physio-
of blood lactate accumulation’ (OBLA), can predict
logical variables measured and the purposes for
endurance performance.
Additional submaximal
which they are used. Further studies are required to
physiological variables related to the blood lactate
test the reliability and validity of PPO quantified
response to incremental exercise include the indi-
from incremental tests of different designs.
vidual anaerobic threshold (IAT), which is deter-
mined by exercise and recovery lactate measure-
1.1.3 Submaximal Lactate and Ventilatory Markers
ments. IAT has been used to quantify an exercise
There are a number of submaximal, physiologi-
steady state in rowing
and reported to induce
cal ‘thresholds’ or ‘inflection’ points, which can be
similar physiological responses during set work ex-
quantified using blood lactate or respiratory ex-
ercise to that of the OBLA.
The day-to-day varia-
change data collected during an incremental test (see
tion (reproducibility) of the corresponding LTs and
figure 1 and figure 2 for examples). Many of these
FBLCs have been shown to be high in trained sub-
methods are based on the observation that lactate
jects using an incremental running protocol com-
levels change suddenly at some critical point and,
prising of 4-minute work stages.
However, more
thus, reflect a threshold phenomenon (for reviews,
research is required concerning the reliability and
agreement of submaximal physiological variables
and how specific procedures effect their quantifica-
tion and relationship.
Submaximal physiological parameters provided
by analysis of respiratory exchange data include the
pulmonary ventilation threshold (VT),
which can
be determined using the expired concentrations of
oxygen and carbon dioxide during an incremental
exercise task (for reviews, see Davis
and Meyer
et al.
). Researchers have also used the terms ‘1st
and 2nd VT’ (also termed the ‘VT’ and ‘point of
respiratory compensation’, respectively) to establish
the exercise intensity in endurance events or for the
purposes of comparison with non-elite ath-
The reproducibility of the 1st and 2nd
VTs has been previously presented,
with these
authors commenting that the 2nd VT is reproduci-
1st VT
2nd VT
Fig. 1. An example of the 1st and 2nd pulmonary ventilation thresh-
olds (VT) calculated from respiratory equivalents of oxygen uptake
) and carbon dioxide release (
), together with pulmonary
ventilation equivalent (
VE) measured during an incremental exer-
cise test to exhaustion.
© 2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (7)
578 Bentley et al.
Lactate (mmol/L)
Lactate (mmol/L)
Lactate (mmol/L)
50 100 150 120 250
Power (watts)
50 100 150 120 250
Power (watts)
50 100 150 120 250
Power (watts)
Power (watts)
50 100 150 200 250
Fig. 2. Examples of submaximal physiological variables obtained from the exercise intensity to blood lactate response obtained from an
incremental exercise test. (a) Lactate threshold (LT); (b) fixed blood lactate concentration (FBLC) [= 4 mmol/L]; (c) marker for estimating the
LT (DMax LT); and (d) marker representing the point of maximum acceleration in the lactate curve (D2Lmax). D2 = estimated second
derivative of the lactate curve.
ble. Given that metabolic acidosis drives pulmonary long duration events, such as the marathon and
ironman triathlon, submaximal physiological pa-
ventilation, some studies have shown that an inflec-
rameters, such as the 1st VT, correspond well to a
tion in blood lactate concentration above baseline
race intensity
and equating heart rate (HR) values
levels is coincident to the 1st VT
or the lowest
corresponding to the 2nd VT may over estimate the
ventilatory equivalent (
VE) for oxygen
race intensity during the cycle stage of a half
VE :
However, this has not always been
ironman triathlon.
Therefore, whilst the intensity
and is dependent upon the training
of exercise during events lasting <1 hour seem to
status of the subjects and the exercise test protocol
correspond well to the 2nd VT, the duration and
intensity of an endurance event should be consid-
It has been demonstrated that submaximal pa-
ered before HR or work rate values can be pre-
rameters, such as the LT or VT, clearly distinguish
scribed to simulate a specific race intensity. The
endurance performance in athletes with similarly
coupling of HR values, which correspond to certain
At the same time, submaximal
submaximal physiological markers, to the race in-
physiological parameters can be used for prescrib-
tensity during an endurance event may also be a
ing exercise intensity that replicates the intensity
function of the incremental test used to determine
experienced during competition.
However, it
these HR values.
has been shown that the intensity of exercise during
a 20km time trial may not agree with that corre-
2. The Physiological Effects of
sponding to the LT.
Others have shown that the
Manipulating an Incremental Exercise
blood lactate concentration during a 40km cycling
Test Protocol
time trial is well above that which corresponds to the
LT or FBLCs of 2 and 4 mmol/L.
Indeed, other
2.1 Manipulating an Incremental Exercise
researchers show that the 2nd VT, which is typically
Test Protocol
at an exercise intensity higher than the LT, reflects
the intensity during a 30-minute cycling time tri-
As described in the previous section, incremental
Another field investigation has shown that in
tests are often used to determine important
© 2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (7)
Exercise Test Design and Analysis 579
predictors of endurance performance such as the LT, elevation in velocity (m/second) or gradient (per-
and PPO or velocity. Therefore, the centage) during treadmill tests, or power output
physiological assessment of the endurance athlete (watts) during cycle exercise. Reducing the length
should accurately measure these variables. In stud- of stages or increasing the magnitude of the work
ies conducted using trained and untrained popula- required to be performed reduces the total duration
tions, a shorter exercise protocol (<60-second stage of the test as the subject is brought to exhaustion
increments) is typically used to measure
much sooner. The incremental exercise test may
and then, on a second day, a submaximal test is used also involve a continuous or discontinuous protocol
to quantify the LT and related variables.
Howev- with rest periods between each stage. In terms of
er, it is also popular to use a single test comprising blood lactate measurements, the type of blood medi-
3-minute stage durations to assess trained sub- um (venous, arterial, mixed arterio-venous) that is
Other scientists working with elite cy- obtained may also influence the concentration of
clists recommend using an incremental test compris- this metabolite due to the overall diffusion of lactate
ing of 60-second stage increments to determine the into the blood.
PPO and VT in cyclists.
It should be highlighted
that it is important for an athlete to consume an
2.2 Effects of Manipulating Stage Duration
optimal, high carbohydrate diet for the purpose of
and Increment in Trained Athletes
inducing full muscle glycogen levels. A number of
Incremental exercise test protocols were original-
studies have demonstrated that maximal and sub-
ly designed to minimise physical discomfort exper-
maximal physiological variables or the metabolic
ienced by untrained subjects in order to obtain a
response to incremental exercise tasks can be influ-
valid measure of aerobic capacity and cardiac func-
enced by pre-test glycogen levels or the diet con-
However, research in untrained subjects
sumed prior to the exercise test.
At the same
suggests that using exercise protocols incorporating
time, acute changes in dietary intake may also influ-
stages lasting >3 minutes may compromise the
ence the metabolic response to incremental exercise
reached, as well as influence other submax-
and physiological variables calculated from blood
imal physiological parameters.
However, the
lactate values.
However, this response may not be
limitation of these studies was that they were con-
the same for the submaximal physiological parame-
ducted with untrained subjects who may respond
ters determined from respiratory gas exchange mea-
differently to an incremental exercise task or who
Hence, the practicing sport scientist
are less motivated to continue at higher exercise
has a number of pre-test issues to contend with.
intensity when compared with trained athletes. Oth-
However, a sport scientist can approach incremental
er researchers have reported the effects of manipu-
exercise testing with a variety of protocols aimed at
lating the stage length during an incremental exer-
determining a number of different physiological
cise test on maximal and submaximal physiological
variables. The diversity of incremental exercise test-
parameters in trained subjects.
ing protocols and the results obtained from these
tests has been recently reported.
However, modi-
2.2.1 Maximum Aerobic Power
fication of the exercise testing protocol can have
There are now a number of studies that have
implications for the variables measured and, hence,
examined whether incremental exercise tests com-
the use of these variables in longitudinal analysis
prising of stages lasting 3 minutes in duration
and performance diagnostics.
would result in a lower
in trained cyclists
An incremental exercise test can be manipulated and rowers.
Pierce et al.
compared four
in a number of different ways to establish the desired incremental rowing tests using stage durations of
physiological adaptation. It is common for the dura- either 60 seconds, 3, 4 or 5 minutes. The results
tion (minutes) of each stage of the test, as well as the showed that there was no difference in
size of the work increment, to be modified during between the 60-second, 3- and 4-minute staged tests.
incremental exercise.
Depending upon the exer- However, the
obtained from the 5-minute
cise mode, the increase may consist of either an stage test was significantly lower. At the same time,
© 2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (7)
580 Bentley et al.
the respiratory exchange ratio was significantly the incremental test design is not known. However,
higher in the 60-second stage test when compared from these data, it could be hypothesised that an
with the remaining incremental exercise tests. In incremental exercise test comprising stages lasting
another study, McNaughton et al.
demonstrated >3 minutes in duration may be more sensitive to
remained unchanged when obtained performance changes with endurance training. Ad-
from an incremental test comprising of 3- or 5-min- ditional studies are required to compare the results
ute stages in cyclists. Similarly, Bishop et al.
of different incremental tests in athletes exposed to
found that there was no difference in
be- endurance training.
tween two incremental exercise tests comprising of
In terms of prescribing training on the basis of
stage increments of 60 seconds (25 watts) or 3
peak exercise testing results, it is likely that an
minutes (10 watts) in duration. Therefore, it appears
incremental test comprising shorter stages will in-
that, at least in trained athletes, the traditional rec-
flate submaximal work rates expressed as a percent-
ommendation of a shorter protocol with large work
age of peak values. Hence, the prescribed work rate
increments to determine
is not necessarily
may be too severe for an athlete and result in subop-
applicable in this subject group. By performing a
timal acute training responses. In terms of quanti-
test with longer work stages (>3 minutes), rather
fying peak physiological measurements for the pur-
than shorter stages with rapid increments, valid
pose of training prescription and monitoring train-
blood lactate measurements may be obtained.
ing, it is recommended that an incremental test
Therefore, other submaximal physiological vari-
comprising of longer stages (>3 minutes) may chal-
ables such as the LT or OBLA may be quantified in
lenge the athlete to a greater extent and may also be
conjunction with
more sensitive to changes in field performance. The
results may also be more valid in terms of prescrib-
ing endurance training intensity; however, this is yet
2.2.2 Maximum Work Rate
to be confirmed. Future studies are needed to ex-
It has been demonstrated that the PPO is lower
amine: (i) the validity of prescribing endurance
when the stage duration is increased from 60
training; (ii) the physiological responses to that
seconds to 5 minutes, and that this may reduce the
training; and (iii) tracking of performance improve-
relationship between this variable and endurance
ments using from maximum work rate obtained
In one study, the PPO was not
from different incremental exercise tests.
significantly different when measured with incre-
mental tests comprising of 3- and 5-minute stages.
In contrast, this study and others
have shown 2.2.3 Submaximal Physiological Parameters
that PPO measured during an increment
al exer-
In terms of the blood lactate response to incre-
cise test comprising of 60-second stages was signifi-
mental exercise, it has been suggested that it is
cantly higher compared with exercise tests compris-
necessary to use stage lengths of 3–6 minutes during
ing of longer stages.
incremental exercise to obtain precise lactate mea-
The implications of employing an incremental surements to determine the desired metabolic inflec-
test with shorter stage duration or shorter overall tion points.
During submaximal exercise of the
length are not well understood in terms of monitor- same relative intensity, the metabolic response may
ing the effects of training. Furthermore, little is differ depending upon the training status of the
known about the consequences of performing incre- subject being assessed.
In one study, it was
mental exercise tests of different design and the shown that the LT was significantly different when
validity of such protocols for monitoring endurance obtained from an incremental test comprising of
training. It has been shown in short-term training longer (8 minute) stages when compared with a
studies that PPO measured from a longer stage test shorter (3 minute) stage test in two groups of sub-
(2.5-minute stages) is much more sensitive to train- jects with markedly different aerobic capacity.
ing induced changes than PPO measured in an incre- This result was interpreted as being related to differ-
mental tests comprising 60-second stages.
ences in lactate diffusion capacity in the well trained
Whether this is a function of the type of training or subjects. Yoshida
has also shown that the kinetics
© 2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (7)
Exercise Test Design and Analysis 581
of lactate diffusion may confound blood lactate re- that incremental exercise protocols comprising work
sults during incremental exercise. Thus, the diffu- stages of >3 minutes in duration may induce more
sion capacity of lactate and the time allowed (i.e. valid blood lactate and respiratory responses. At the
work duration) for this diffusion to occur before an same time, incremental exercise protocols compris-
increment in work rate may influence the blood ing stages lasting 3 minutes can be used to measure
lactate response to exercise.
This, in turn, could maximal physiological values and can be coupled to
influence submaximal physiological measurements, valid submaximal physiological variables. Hence,
in particular the exercise intensity corresponding to incremental protocols of this design represent a bet-
a 2 or 4 mmol/L FBLC.
ter approach to holistic performance diagnostics.
Some studies have shown that modifying the
Other research investigations have compared
length of stages in an incremental test will influence
submaximal physiological inflection points obtained
the intensity corresponding to the VT or LT and the
from incremental exercise tests comprising different
relationship of this variable to endurance perform-
stage durations in trained athletes.
ance in trained cyclists.
Despite these studies,
et al.
compared the
, velocity and HR at the
there are limited data that have examined the rela-
LT, and FBLCs of 2, 2.5 and 4 mmol/L obtained
tionship between submaximal physiological vari-
from two incremental exercise tests comprising of
ables obtained from incremental tests of different
discontinuous stages of 10 minutes in duration or
designs and endurance performance. Future research
continuous 3-minute stages. They found that in a
is required to examine whether the incremental exer-
group of relatively well trained runners, the speed
cise protocol influences the relationship between
corresponding to the LT did not differ
submaximal and maximal physiological parameters,
between tests. However, the
and velocity at a
as well as endurance performance.
FBLC of 2 mmol/L was significantly higher in the
Modification of an incremental exercise test pro-
10-minute discontinuous test. In contrast, Foxdal et
tocol will influence the LT and OBLA, as well as the
concluded that exercise tests using stages of
and the maximum work rate. On the basis
4–6 minutes in duration do not result in steady-state
of these studies, it also seems that in order to obtain
blood lactate concentrations. Furthermore, these au-
a valid measure of submaximal blood lactate con-
thors suggested that when determining the OBLA
centrations, longer exercise protocols are needed to
threshold in trained subjects, stages of 8 minutes in
allow lactate diffusion before an increment in work
duration should be used.
occurs. However, using a test comprising longer
Other studies have shown that the work rate
stages may compromise the
and maximum
corresponding to the VT is different when measured
work rate measurements. While conducting two
in incremental exercise tests comprising either
tests on separate days is one solution, it may be
60-second or 3-minute stages.
This finding is in
considered too time consuming for athletic popula-
contrast with that of Amann et al.,
who showed
tions. In contrast though, more recent work has
that there was no difference in the VT when ob-
demonstrated that there may be no difference in the
tained from two tests comprising 60-second or
LT and OBLA when obtained from incremental
3-minute stages. Weston et al.
have also shown
tests comprising stages of 3- or 5-minute duration in
that an incremental test comprising ‘fast’ or ‘slow’
well trained cyclists.
Hence, it may be possible to
increments resulted in no significant difference in
recommend a single incremental testing protocol
physiological parameters or the VT in trained ath-
that is valid for measuring both maximal and sub-
letes. However, in both of these studies, the magni-
maximal physiological variables.
tude of the work rate increment was different.
These studies demonstrate inconsistency in terms
3. Calculation of Markers of Endurance
of manipulating the exercise test protocol and mea-
Performance from Lactate Curves
surement of the VT. More studies are required to
examine the validity of measuring the VT using While the actual incremental protocol used to
different incremental protocol designs in athletes. elicit the lactate response may be crucial in deter-
These investigations considered, it is recommended mining the various submaximal inflection points,
© 2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (7)
582 Bentley et al.
the treatment of the blood lactate data generated initial and final lactate reading. The initial and final
from an incremental exercise test may also be anoth- work rate, where the lactate data are collected, may
er important factor. To date, there is no definitive demonstrate considerable variability, which will
model to describe the blood lactate response to have a direct influence on the reliability and validity
incremental exercise where the emphasis is on mod- of this marker.
The choice as to where the data
elling the data and not the process that generated the collection is stopped is also a vital issue to consider.
data. The marker has been demonstrated to have good
reliability and appears to correlate well with the
The main controversy surrounding blood lactate
average power output in cycle time trials.
analysis is whether there is a breakpoint (i.e. LT)
present in the lactate curve or whether lactate in-
Several other lactate markers, which do not at-
creases as a smooth function. It is important to note
tempt to estimate a breakpoint, have been suggested
that the presence of a breakpoint implies a disconti-
based on the assumption that during incremental
nuity in the first derivative of the lactate curve. This
exercise, the change in blood lactate does not dis-
assumption does not imply that the lactate curve
play a threshold (i.e. breakpoint) phenomenon. Typ-
itself is non-continuous, as highlighted by Mor-
ically, these markers have no physiological interpre-
tation, but appear to estimate work rates correspond-
ing to points of curvature on the lactate curve.
Traditionally, the LT was determined subjective-
ly from plots of the lactate concentration versus
Endurance markers representing subjective fea-
work. Lundberg et al.
proposed fitting a two-part
tures of a lactate curve have been proposed. One is
linear regression, where the estimated work rate
the intensity corresponding to a FBLC, typically
corresponding to the intersection of the two lines is
4 mmol/L,
which represents a ceiling value for
the LT (i.e. a broken stick regression model). The
lactate. A second, is the intensity preceding an in-
estimate of LT is found by identifying the LT corre-
crease in lactate concentration of 1 mmol/L above
sponding to the model with the minimum mean
baseline, where the lactate curve is estimated using a
squared error.
polynomial fit of degree three.
Both of these
markers are estimated using inverse prediction.
Criticisms of the LT marker include that it may
These markers are subjective in nature and, hence,
be estimating a feature of the curve that does not
this may influence reproducibility. Smoothing of
actually exist and that it is using linear regression,
datasets ensures that the lactate curve is fitted to the
which is quite sensitive to outliers in small datasets
data locally, such that regions of considerable varia-
(i.e. there can be a considerable difference in the
bility will not overly influence or ‘distort’ the esti-
estimate of the LT following small changes in the
mate of the true curve from that region onwards.
recorded lactate). Therefore, the use of a line to
summarise a curvilinear relationship is questiona-
The intensity corresponding to the point of maxi-
ble. One solution to this problem has been the use of
mum acceleration in the lactate curve has been pro-
a log transformation of both the work and blood
posed as a marker.
This marker, the D2LMax,
lactate concentration in an attempt to gain a better
represents a unique feature of the lactate curve and
estimate of the LT.
its estimation is not influenced by variability at early
The DMax is an alternative objective marker for and late workloads. The D2LMax is estimated using
estimating the LT.
This marker is the intensity smoothing splines and is not influenced by initial
corresponding to the point that yields the maximum variation or the choice of end point of the testing
perpendicular distance from a line joining the first protocol. The marker demonstrates good reliability
and last lactate measurements to the estimated lac- and correlates well with endurance performance.
tate curve.
The DMax marker represents the exer- The D2LMax may be estimated using smoothing
cise intensity where the slope of the line joining the splines; however, a simple discrete estimator has
first and last lactate measurements is equal to the also been proposed.
Note, that estimates of the
slope of the lactate curve (typically estimated using precision of each of the markers (i.e. the standard
a degree three polynomial). The main criticism of error) should be considered when determining if
the DMax marker is its dependence on both the changes in a lactate marker are a feature of a real
© 2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (7)
Exercise Test Design and Analysis 583
systematic change in endurance level or an artefact curve); and (ii) using the lactate curve itself (rather
than any summary features) for longitudinal com-
of imprecision in the estimation process.
parisons (e.g. across a season) using modern statisti-
There does not appear to be a definitive ‘best’
cal techniques such as Functional Data Analysis
marker in terms of the predictive power of the blood
(Ramsey and Silverman
endurance markers and, thus, the LT marker may
still be a useful endurance marker while not repre-
4. Conclusions
senting a transition. The correlation between each
marker and endurance performance has been as-
It is typical for researchers to use maximal and
sessed using the average power output during a
submaximal physiological variables to predict en-
cycle time trial.
The correlation of each marker
durance performance and design training program-
and endurance performance is given in table I,
mes. A common methodological constraint in all
where those markers that were significantly corre-
published studies has been the length of the stages
lated with endurance are flagged. There was no
during an incremental exercise test and, therefore,
consistent best marker and there was no evidence
the total duration of the incremental test used. At the
that those markers that were individually signifi-
same time, the approach to analysing a typical blood
cantly related to performance were indeed signifi-
lactate-to-work rate curve is varied with the validity
cantly different from each other. Multiple linear
of the numerous physiological markers not well
regression techniques suggested that a selection of
understood. It is possible that modification of the
markers was more useful than any solitary mark-
incremental exercise test protocol and the analysis
allowing for a better prediction of the re-
procedure may affect maximal and submaximal
sponse of interest (e.g. power output, race time) to
physiological parameters. These changes may be
be made. However, the use of these markers for
significant in terms of using these physiological
prescribing training or determining training-induced
variables to monitor the effects of training assess-
changes in performance need to be established.
ment and for recommendation of exercise or per-
formance prediction. However, there is a limited
Interesting research areas in the field of model-
amount of work in trained populations investigating
ling data obtained from incremental exercise testing
the reliability and validity of physiological variables
include: (i) modelling the cumulative effect of lac-
obtained from incremental exercise tests comprising
tate on performance (i.e. the area under the lactate
of stages of 1–5 minutes in duration. From the
available literature, it appears that an incremental
test comprising of 3-minute work increments pro-
vides the most reliable and valid measures of endur-
ance performance. Future studies in trained athletes
are necessary to determine the reliability and validi-
ty of maximum work rate, as well as the sensitivity
of this variable to training with other submaximal
physiological variables measured in different incre-
mental exercise tests.
No sources of funding were used to assist in the prepara-
tion of this article. The authors have no conflicts of interest
that are directly relevant to the content of this article.
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Table I. Correlation coefficient of blood lactate endurance markers
with power output in cyclists
Lactate endurance Dataset 1 Dataset 2
marker (Bentley et al. 2001)
(Bishop et al.
Average Average Average power
power output power output output (watts)
(watts) (watts) 60-min TT
20-min TT 90-min TT (n = 24)
(n = 9) (n = 9)
LT 0.62 0.76* 0.77*
Log LT 0.66* 0.86* 0.62*
FBLC 4 mmol/L 0.23 0.54 0.80*
1 mmol/L rise 0.32 0.77* 0.82*
above baseline
0.31 0.35 0.84*
D2LMax 0.64 0.78* 0.76*
DMax = marker for estimating the LT; D2LMax = marker
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threshold; TT = time trial; * p < 0.05.
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... O teste incremental é um protocolo padronizado para determinação das variáveis fisiológicas submáximas e máximas, podendo sofrer alterações na sua estrutura, como a intensidade inicial, duração e intensidade dos incrementos (BENTLEY, NEWELL et al., 2007). ...
... Os testes podem sofrer essas modificações para uma avaliação mais adequada à população e variáveis que se pretende estudar, sendo que, a modificação na duração de cada estágio é a forma mais comum de adaptação do teste incremental (BENTLEY, NEWELL et al., 2007). ...
... Coyle (1995) verificou em sujeitos treinados e destreinados que estágios curtos (< 60 segundos) podem ser utilizados para mensuração do V O2max. No entanto, os testes com estágios de 3 minutos tem sido os mais utilizados para avaliação de atletas (BENTLEY, NEWELL et al., 2007). Nesse sentido, Kuipers, Rietjens et al., (2003) No ambiente clínico, a fadiga constante apresenta-se como um sintoma comum em pacientes com disfunções cardíacas, sendo geralmente atribuída a falta de perfusão no músculo esquelético no repouso e durante o exercício, resultando em isquemias (WILSON, MARTIN et al., 1984). ...
Full-text available
The maximal lactate steady state (MLSS) and critical power (CP) represent the transition from heavy to severe domain and present important relationship with aerobic performance. Due the difficults on determination of these intensities, physiological index derived from incremental tests has been used in estimation. The muscle deoxihemoglobin ([HHb]BP) derivated of near infrared spectroscopy (NIRs) report the muscle oxygen extraction, which present a plateau in response during incremental test, identifying a break point ([HHb]BP), that has been associated with some index of second physiological transition and MLSS. This association, however, has not yet been determined in rowing, sport in which index of second physiological transition overestimated the MLSS. The aim of the present study was to compare the MLSS and CP intensities with the [HHb]BP in vastus lateralis muscle in incremental test with (INC3min) and without (INC1min) recovery in rowing ergometer. In addition, to verify their correlation with performance. Fourteen rowers (age: 26 ± 13 years; body mass: 81.0 ± 7.6 kg; height: 1.82 ± 0.05 m; 2000m time: 415 ± 18 s) performed: I) anthropometric assessment; II) INC3min, with initial load of 130 W and 30 W exercise steps of 3-min and 30 s of passive recovery; III) MLSS determination, through 30-min constant load tests; IV) INC1min, with initial load of 130 W and 30 W exercise steps of 1-min without recovery and V) CP determination through 500, 1000, 2000 and 6000m tests. The vastus lateralis muscle oxygenation was measured by NIRs for determination of [HHb]BP in INC3min ([HHb]BP3min) and INC1min ([HHb]BP1min), that was compared with power of MLSS, CP and first and second physiological transition indexes derivate of blood lactate, heart rate, ventilation and performance tests. The data were expressed as mean and ± SD. The comparison were performed using ANOVA one-way. Pearson correlation with confidence intervals of 95%, mean difference (Δ) and typical error of estimate (TEE) for such indexes with significance level of p < 0.05. The [HHb]BP1min (204 ± 29W) and [HHb]BP3min (207 ± 29W) showed low correspondence from each other (Δ: -3.4%; TEE: 13.2%; r = 0.51), overestimated the MLSS (Δ: 8.4 and 13.1%; TEE: 15.3 and 15.6%) and underestimated the CP (Δ: -20.4% and -17.4%; TEE: 12.3% and 10.5%). The CP was higher than MLSS (Δ: 37.6%; TEE: 10.8%; p < 0.01). The 18 second transition indexes overestimated MLSS (Δ: 12.5 to 44.9%; TEE: 5.6 to 14.3%), while LL2,0 (186 ± 27 W) and VT1 (193 ± 18 W) presented the smallest TEE (11.0 and 9.5%) and Δ (-2.3 and 4.0%), respectively, with magnitudes from trivial to medium. The time (r = -0.87) and mean power (r = 0.86) of 1000m test showed a very large correlation with MLSS. The [HHb]3min and [HHb]1min presented low correlations with performance tests. In conclusion, despite the [HHb]3min and [HHb]1min did not show significant diferences from MLSS, it was observed high variability with high TEE and mean difference that suggest a small correspondence between these indexes. In addition, the CP was higher than [HHb]BP and MLSS. Taking into account the better association of first physiological transition index with the MLSS, which clearly underestimated CP, it is possible that these markers correspond to the lower and the upper boundaries of the heavy domain on rowing exercise.
... Physiological thresholds such as lactate thresholds or ventilatory thresholds can have a direct affect on endurance performance and are used to prescribe exercise intensity for training, competition, and different tests (Bentley et al., 2007). Lactate thresholds can be determined using different methods, such as fixed blood lactate concentration (FBLC) or onset of blood lactate accumulation (OBLA), which determine the first lactate threshold at 2 mmol/L and the second lactate threshold at 4 mmol/L, respectively (Bentley et al., 2007;Kindermann et al., 1979). ...
... Physiological thresholds such as lactate thresholds or ventilatory thresholds can have a direct affect on endurance performance and are used to prescribe exercise intensity for training, competition, and different tests (Bentley et al., 2007). Lactate thresholds can be determined using different methods, such as fixed blood lactate concentration (FBLC) or onset of blood lactate accumulation (OBLA), which determine the first lactate threshold at 2 mmol/L and the second lactate threshold at 4 mmol/L, respectively (Bentley et al., 2007;Kindermann et al., 1979). Individual thresholds are determined using different formulas (6). ...
... Physiological thresholds such as lactate thresholds or ventilatory thresholds, are usually determined by incremental tests as a standard procedure (Bentley et al., 2007). But there is one main problem with maximal incremental tests to establish a lactate threshold, as there is a lack of consensus on the protocol to be used, i.e., in the variables of: total duration, duration of each stage, change in intensity of each stage, and total number of stages or incremental stages (Bentley et al., 2007;Jamnick et al., 2018). ...
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Introduction: The study aims to explore whether NIRS derived data can be used to identify the second ventilatory threshold (VT2) during a maximal incremental treadmill test in non-professional runners and to determine if there is a correlation between SmO 2 and other valid and reliable exercise performance assessment measures or parameters for maximal incremental test, such as lactate concentration (LT), RPE, HR, and running power (W). Methods: 24 participants were recruited for the study (5 women and 19 men). The devices used consisted of the following: i) a muscle oxygen saturation analyzer placed on the vastus lateralis of the right leg, ii) the Stryd power meter for running, iii) the Polar H7 heart rate band; and iv) the lactate analyzer. In addition, a subjective perceived exertion scale (RPE 1-10) was used. All of the previously mentioned devices were used in a maximal incremental treadmill test, which began at a speed of 8 km/h with a 1% slope and a speed increase of 1.2 km/h every 3 min. This was followed by a 30-s break to collect the lactate data between each 3-min stage. Spearman correlation was carried out and the level of significance was set at p < 0.05. Results: The VT2 was observed at 87,41 ± 6,47% of the maximal aerobic speed (MAS) of each participant. No relationship between lactate data and SmO 2 values ( p = 0.076; r = −0.156) at the VT2 were found. No significant correlations were found between the SmO 2 variables and the other variables ( p > 0.05), but a high level of significance and strong correlations were found between all the following variables: power data (W), heart rate (HR), lactate concentration (LT) and RPE ( p < 0.05; r > 0.5). Discussion: SmO 2 data alone were not enough to determine the VT2, and there were no significant correlations between SmO 2 and the other studied variables during the maximal incremental treadmill test. Only 8 subjects had a breakpoint at the VT2 determined by lactate data. Conclusion: The NIRS tool, Humon Hex, does not seem to be useful in determining VT2 and it does not correlate with the other variables in a maximal incremental treadmill test.
... Conversely, if a proxy of effort is measured to gauge the impact of an intervention, it functions as the dependent variable. For instance, consider stepwise incremental exercise tests performed on treadmills or cycle ergometers used to assess maximal aerobic capacity [52]. The mechanical power (watts) or running velocity (km/h) is incrementally and systematically increased until participants reach physical exhaustion [52]. ...
... For instance, consider stepwise incremental exercise tests performed on treadmills or cycle ergometers used to assess maximal aerobic capacity [52]. The mechanical power (watts) or running velocity (km/h) is incrementally and systematically increased until participants reach physical exhaustion [52]. In such tests, the manipulated effort (e.g., running velocity) is the independent variable, while the maximal oxygen consumption is the dependent variable, serving as a proxy of effort. ...
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Effort and the perception of effort have been extensively studied across multiple disciplines, resulting in disparate definitions across the literature. Inconsistencies in definitions impede scientific progress by blocking effective communication between and within disciplines. Here, we introduce a resource-based framework that comprehensively defines and connects effort and perception of effort, and provide a detailed analysis of these constructs. We define effort in a way that applies to all biological entities, voluntary and involuntary actions, and successful and unsuccessful actions. We define perception of effort such that it builds on our definition of effort without conflating it with other experiences. Our definition of perception of effort also aligns with various explanations regarding its proposed functions and mechanistic underpinnings. We explore the latent nature of these constructs, their employment as independent and dependent variables, and their associations. Our framework also seeks to bridge the gap between cognitive and physical effort and perception of effort, which have been primarily developed in isolation. We anticipate that our framework will facilitate a deeper understanding of these constructs, refine research methodologies and promote interdisciplinary collaborations.
... Between each work step, a 1 min passive recovery interval is added to observe the onset desaturation response of each work step. By employing this protocol, the progressive effects of each workload on all performance and physiological markers can be observed in relative isolation in a time efficient single session (27,28). Recently, this protocol has been used to compare SmO 2 with [BLa], using a similar rationale outlined previously (28). ...
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Introduction Wearable near-infrared spectroscopy (NIRS) measurements of muscle oxygen saturation (SmO 2 ) demonstrated good test–retest reliability at rest. We hypothesized SmO 2 measured with the Moxy monitor at the vastus lateralis (VL) would demonstrate good reliability across intensities. For relative reliability, SmO 2 will be lower than volume of oxygen consumption (V̇O 2 ) and heart rate (HR), higher than concentration of blood lactate accumulation ([BLa]) and rating of perceived exertion (RPE). We aimed to estimate the reliability of SmO 2 and common physiological measures across exercise intensities, as well as to quantify within-participant agreement between sessions. Methods Twenty-one trained cyclists completed two trials of an incremental multi-stage cycling test with 5 min constant workload steps starting at 1.0 watt per kg bodyweight (W·kg ⁻¹ ) and increasing by 0.5 W kg ⁻¹ per step, separated by 1 min passive recovery intervals until maximal task tolerance. SmO 2 , HR, V̇O 2 , [BLa], and RPE were recorded for each stage. Continuous measures were averaged over the final 60 s of each stage. Relative reliability at the lowest, median, and highest work stages was quantified as intraclass correlation coefficient (ICC). Absolute reliability and within-subject agreement were quantified as standard error of the measurement (SEM) and minimum detectable change (MDC). Results Comparisons between trials showed no significant differences within each exercise intensity for all outcome variables. ICC for SmO 2 was 0.81–0.90 across exercise intensity. ICC for HR, V̇O 2 , [BLa], and RPE were 0.87–0.92, 0.73–0.97, 0.44–0.74, 0.29–0.70, respectively. SEM (95% CI) for SmO 2 was 5 (3–7), 6 (4–9), and 7 (5–10)%, and MDC was 12%, 16%, and 18%. Discussion Our results demonstrate good-to-excellent test-retest reliability for SmO 2 across intensity during an incremental multi-stage cycling test. V̇O 2 and HR had excellent reliability, higher than SmO 2 . [BLa] and RPE had lower reliability than SmO 2 . Muscle oxygen saturation measured by wearable NIRS was found to have similar reliability to V̇O 2 and HR, and higher than [BLa] and RPE across exercise intensity, suggesting that it is appropriate for everyday use as a non-invasive method of monitoring internal load alongside other metrics.
... Modification of the multistage progressive test protocol and lactate analysis procedures may affect physiological parameters. These changes can be significant, in terms of interpreting physiological variables in order to monitor the effects of particular training or to predict the level of ability development (Bentley, Newell & Bishop, 2007). ...
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Judo is often referred to as an explosive sport, which requires great anaerobic strength and capacity, with a well-developed aerobic system. Attaining a high level of physical fitness, strength, and fatigue tolerance is essential for achieving success in competition. Fatigue leads to decreased muscle strength, prolonged reaction time, reduced agility, neuromuscular coordination, overall body speed, concentration, and agility. The intensity at which this phenomenon occurs is known as the lactate threshold. The primary objective of the planned research was to establish a link between maximal oxygen consumption (VO 2 max), lactate metabolism, and the situational efficiency of selected young judoists. The sample consisted of 30 cadet and junior judo athletes from the national teams of Serbia (average age of 16.43±0.76 years, body height of 176.94±5.15 cm, and body weight of 69.71±10.64 kg). The research employed precisely standardized protocols and modern equipment to determine anthropometric characteristics, and the values of maximal oxygen consumption, lactate thresholds, and the index of a specific judo fitness test among the selected young judo athletes. Based on the obtained results, there was a moderate negative correlation between VO 2 max and the index of the special judo fitness test, as well as a low correlation between the first lactate threshold (PLAP) and the second lactate threshold (DLAP) with the index of the special judo fitness test (ISJFT). Additionally, a moderate negative correlation was found between VO 2 max and anthropometric parameters, while PLAP and DLAP exhibited low correlations with anthropometric parameters. The research results quantitatively illustrate the physiological adaptation of the top young judo athletes to the physical demands encountered during years of specific training. The proposed battery of tests can be utilized to assess the functional status of competitors more accurately and determine the competition profile for elite judo athletes.
... The use of heart rate variability (HRV), maximal rate of heart rate increase (rHRI), and heart rate recovery (HRR) as alternative measures to indirectly assess VO2max has gained increasing attention in recent years. VO2max is a laboratory-measured parameter that is considered the gold standard for assessing cardiorespiratory tness, and is associated with numerous health bene ts and sports performance (1,2,(7)(8)12). However, the practical limitations of direct maximal oxygen consumption (VO2max) measurement, such as expensive equipment and specialized personnel, have motivated researchers to explore the potential of non-invasive and low-cost measures such as HRV, rHRI, and HRR. ...
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Background The peak oxygen uptake (VO2peak) is considered the most reliable parameter for evaluating cardiorespiratory fitness and guiding physical training. However, not everyone has access to VO2peak measurements. As a more accessible alternative, heart rate (HR) variables have emerged. Aim To explore the correlation between HR responses during rest, exercise, recovery, and VO2peak. Methods Thirteen healthy men participated in the study. Resting HR variability and parameters were recorded for 10 minutes using a heart rate monitor while participants were seated. A maximal intermittent treadmill test was conducted to determine the maximum rate of HR increase (rHRI) and obtain VO2peak data (33.53 ± 8.22 mL/kg/min). The test speed was set based on the International Physical Activity Questionnaire (IPAQ) classification: 8 km/h for inactive or insufficiently active individuals, and 10 km/h for active and highly active individuals. Additionally, HR recovery (HRR) was measured during a 10-minute seated recovery period. Results Significant correlations were observed between resting HR (r = -0.78, p = 0.001), average RR interval (iRR) (r = 0.73, p = 0.004), percentage of iRR differences exceeding 50 ms (pNN50) (r = 0.64, p = 0.001), HR (r = -0.60, p = 0.003), and VO2peak. However, no significant correlation was found between rHRI and VO2peak (r = 0.38, p = 0.2). Conclusion Resting HR parameters, HR variability, and HRR showed significant associations with VO2peak. These HR variables can be useful alternatives for assessing and prescribing physical training when direct measurement of VO2peak is not feasible.
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INTRODUÇÃO: O goalball é um esporte paralímpico desenvolvido especialmente para pessoas com deficiência visual. Embora a dinâmica do jogo ocorra por ações intermitentes subsidiadas pelo metabolismo anaeróbio alático, a exigência da modalidade é predominantemente aeróbia. Dessa forma, considerando a importância desse parâmetro para a manutenção e recuperação dos esforços, sua avaliação é fundamental para o treinamento do goalball. OBJETIVO: Avaliar um protocolo progressivo específico para a determinação da potência aeróbia máxima em jogadores de goalball. MÉTODOS: Um teste progressivo, denominado Fit-Go, foi desenvolvido e aplicado em 10 jogadores do sexo masculino. A reprodutibilidade e validade do Fit-Go foram testadas, respectivamente, com base nos momentos teste e reteste e, reteste e fase de verificação. RESULTADOS: O teste Fit-Go demonstrou reprodutibilidade ao assumir que: (i) as análises de variância do consumo de oxigênio e frequência cardíaca não apresentaram efeitos entre os momentos teste e reteste, e; (ii) variações similares foram encontradas na percepção subjetiva de esforço. O Fit-Go se mostrou válido para as análises da frequência cardíaca máxima e concentração pico de lactato, uma vez que essas variáveis não apresentaram diferenças para ambas as situações de validação (i.e. reteste e esforço de verificação). A efetividade do Fit-Go no cumprimento de três ou mais critérios de exaustão confirmaram a funcionalidade do teste como um protocolo específico de intensidade progressiva para jogadores de goalball. CONCLUSÃO: Treinadores(as) e cientistas do esporte podem utilizar o Fit-Go como protocolo progressivo máximo para jogadores(as) de goalball.
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Over the last few years, portable Near-Infrared Spectroscopy (NIRS) technology has been suggested for determining metabolic/ventilator thresholds. This systematic review and meta-analysis aimed to assess the reliability of a portable muscle oxygenation monitor for determining thresholds during exercise testing. The proposed PICO question was: Is the exercise intensity of muscle oxygenation thresholds, using portable NIRS, reliable compared with lactate and ventilatory thresholds for exercise intensity determined in athletes? A search of Pubmed, Scopus and Web of Science was undertaken and the review was conducted following PRISMA guidelines. Fifteen articles were included. The domains which presented the highest biases were confounders (93% with moderate or high risk) and participant selection (100% with moderate or high risk). The intra-class correlation coefficient between exercise intensity of the first ventilatory or lactate threshold and the first muscle oxygenation threshold was 0.53 (obtained with data from only 3 studies), whereas the second threshold was 0.80. The present work shows that although a portable muscle oxygenation monitor has moderate to good reliability for determining the second ventilatory and lactate thresholds, further research is necessary to investigate the mathematical methods of detection, the capacity to detect the first threshold, the detection in multiple regions, and the effect of sex, performance level and adipose tissue in determining thresholds.
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Backround Foot strike pattern (FSP) is defined by the way the foot makes initial ground contact and is influenced by intrinsic and extrinsic factors. This study investigated the effect of running speed on asymmetries of FSP. Methods Seventeen female and nineteen male soccer players performed an incremental running test on an instrumented treadmill starting at 2.0 m/s until complete exhaustion. Force plate data were used to categorize foot strikes into rearfoot (RFS) and non-rearfoot strikes. Additionally, peak vertical ground reaction force (peakGRF) and stride time were calculated. The symmetry index (SI) was used to quantify lateral asymmetries between legs. Results The SI indicated asymmetries of the rate of RFS (%RFS) of approximately 30% at slow running speed which decreased to 4.4% during faster running speed (p = 0.001). There were minor asymmetries in peakGRF and stride time at each running stage. Running speed influenced %RFS (p < 0.001), peakGRF (p < 0.001) and stride time (p < 0.001). Significant interaction effects between running speed and sex were shown for %RFS (p = 0.033), peakGRF (p < 0.001) and stride time (p = 0.041). Conclusion FSP of soccer players are asymmetric at slower running speed, but symmetry increases with increasing speed. Future studies should consider that FSP are non-stationary and influenced by running speed but also differ between legs.
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Backround: Oxygen uptake (VO 2 ) is one of the most important measures of fitness and critical vital sign. Cardiopulmonary exercise testing (CPET) is a valuable method of assessing fitness in sport and clinical settings. There is a lack of large studies on athletic populations to predict VO 2max using somatic or submaximal CPET variables. Thus, this study aimed to: (1) derive prediction models for maximal VO 2 (VO 2max ) based on submaximal exercise variables at anaerobic threshold (AT) or respiratory compensation point (RCP) or only somatic and (2) internally validate provided equations. Methods: 4424 male endurance athletes (EA) underwent maximal symptom-limited CPET on a treadmill (n=3330) or cycle ergometer (n=1094). The cohort was randomly divided between: variables selection (n runners =1998; n cyclist =656), model building (n runners =666; n cyclist =219) and validation (n runners =666; n cyclist =219). Random Forest was used to select the most significant variables. Models were derived and internally validated with Multiple Linear Regression. Results: Runners were 36.24±8.45 yrs.; BMI=23.94±2.43 kg·m ⁻² ; VO 2max =53.81±6.67 mL·min ⁻¹ ·kg ⁻¹ . Cyclists were 37.33±9.13 yr.; BMI=24.34±2.63 kg·m ⁻² ; VO 2max =51.74±7.99 mL·min ⁻¹ ·kg ⁻¹ . VO 2 at AT and RCP were the most contributing variables to exercise equations. Body mass and body fat had the highest impact on the somatic equation. Model performance for VO 2max based on variables at AT was R ² =0.81, at RCP was R ² =0.91, at AT&RCP was R ² =0.91 and for somatic-only was R ² =0.43. Conclusions: Derived prediction models were highly accurate and fairly replicable. Formulae allow for precise estimation of VO 2max based on submaximal exercise performance or somatic variables. Presented models are applicable for sport and clinical settling. They are a valuable supplementary method for fitness practitioners to adjust individualised training recommendations. Funding: No external funding was received for this work.
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To quantify training intensity in 13 nationally ranked male distance runners, training heart rates, environmental factors, and motivational factors were recorded throughout a 6-8 wk period of normal training. Variation in motivational and environmental factors such as intended effort, terrain, and running with companions altered training session mean heart rates by up to 4.min-1 (standard deviation). Heart rates and blood lactate concentrations, recorded in a series of steady-state treadmill runs, were used to convert training session mean heart rates to mean training speeds (TS) and to derive a measure of the anaerobic threshold (AT, the treadmill speed at a blood lactate concentration of 4 mmol.l-1). TS (15.6 +/- 1.4 km.h-1, mean +/- SD) was considerably lower than AT (20.2 +/- 1.1 km.h-1) in all subjects (P less than 0.001). Relative TS (TS expressed as a fraction of AT) differed significantly (P less than 0.001) between subjects and correlated significantly with the distance of the event for which the subject was training (r = 0.59, P less than 0.05). Relative TS may therefore be determined by the subject's or coach's perception of the appropriate intensity for the event. If the AT is the optimum training intensity, these subjects have considerable scope for improvement.
Anaerobic threshold as a basic criterion of training recommendation can be estimated by various parameters. The purpose of this study was to investigate the relationship and the reproducibility of ventilatory, lactate-derived and catecholamine thresholds of an incremental treadmill exercise. Therefore, 11 male subjects underwent two incremental treadmill tests within 7 days. The lactate threshold (LT) was determined at the lowest Value of the lactate-equivalent (ratio lactate/performance). The individual anaerobic threshold (IAT) was calculated at LT + 1.5 mmol/L lactate. The ventilatory thresholds, using mass-spectrometry, were defined by the V-slope method (AT) and at the deflection point of end-tidal CO2 (ET-CO2) concentration (RCP). The thresholds of epinephrine (TE) and norepinephrine (TNE) were calculated in the manner of LT. The running velocities were highly reproducible at LT (test-retest correlation coefficient r = 0.90), IAT (r = 0.97), AT (r = 0.88) and RCP (r = 0.95). By contrast TE (r = 0.49) and TNE (r = 0.46) showed a poor reproducibility. TE and TNE occurred 5 - 11 % below LT and AT with a low correlation to LT and AT. LT was found 4 % below AT, both were correlated with r = 0.70 (p < 0.01, test 1) and r = 0.95 (p < 0.01, test 2). IAT occurred 7 - 8% above RCP, in both tests a close correlation was found between IAT and RCP of r = 0.97 (p < 0.01). In summary, the ventilatory and lactate-derived thresholds show a high and similar reproducibility, but the catecholamine threshold does not. In the present exercise protocol, there are systematic differences between the lactate-derived and ventilatory thresholds, in spite of a close relationship, and these must be taken into account in recommendations derived for training.
A new type of negative deuterium ion source for the neutral particle injection in the fusion research is proposed. The element of the ion source is made of a bilayer of vanadium or palladium metal and a silicon semiconductor. The D− ions are formed with the cascade processes which involve the dissociation of D2’s when they are dissolved into the element, the electronic resonance transition from the Si surface to D(1s) diffusing through the element, and the detachment of the resultant D− ion from the surface. The estimations show that in an ideal case, the obtainable current density of D− ions is about 27 mA/cm2 and that the neutral component leaving the surface is about 18.5&percnt; of the D− ion current.
The purposes of this study were firstly to determine the relationship between the peak power output (W peak) and maximal oxygen uptake (VO2max) attained during a laboratory cycling test to exhaustion, and secondly to assess the relationship betweenW peak and times in a 20-km cycling trial. One hundred trained cyclists (54 men, 46 women) participated in the first part of this investigation. Each cyclist performed a minimum of one maximal test during whichW max andVO2max were determined. For the second part of the study 19 cyclists completed a maximal test for the determination ofW peak, and also a 20-km cycling time trial. Highly significant relationships were obtained betweenW peak andVO2max (r=0.97,P<0.0001) and betweenW peak and 20-km cycle time (r= –0.91,P<0.001). Thus,W peak explained 94% of the variance in measuredVO2max and 82% of the variability in cycle time over 20 km. We concluded that for trained cyclists, theVO2max can be accurately predicted fromW peak, and thatW peak is a valid predictor of 20-km cycle time.
We postulated that the commonly observed constant linear relationship between [(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} } and work rate during cycle ergometry to exhaustion is fortuitous and not due to an unchanging cost of external work. Therefore we measured [(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} } continuously in 10 healthy men during such exercise while varying the rate of work incrementation and analyzed by linear regression techniques the relationship between [(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} } and work rate ( [(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} } / [(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} } / wr in ml min–1 W–1 to be 11.20.15, 10.20.16, and 8.80.15 for the 15, 30, and 60 Wmin–1 tests, respectively, expressed as mlJ–1 the values were 0.1870.0025, 0.1700.0027 and 0.1470.0025. The slopes of the lower halves of the 15 and 30 Wmin–1 tests were 9.90.2 mlmin–1W–1 similar to the values for aerobic work reported by others. However the upper halves of the 15, 30, and 60 Wmin–1 tests demonstrated significant differences: 12.40.36 vs 10.50.31 vs 8.70.23 mlmin–1W–1 respectively. We postulate that these systematic differences are due to two opposing influences: 1) the fraction of energy from anaerobic sources is larger in the brief 60 Wmin–1 tests and 2) the increased energy requirement per W of heavy work is evident especially in the long 15 Wmin–1 tests.
Anaerobic and aerobic-anaerobic threshold (4 mmol/l lactate), as well as maximal capacity, were determined in seven cross country skiers of national level. All of them ran in a treadmill exercise for at least 30 min at constant heart rates as well as at constant running speed, both as previously determined for the aerobic-anaerobic threshold. During the exercise performed with a constant speed, lactate concentration initially rose to values of nearly 4 mmol/l and then remained essentially constant during the rest of the exercise. Heart rate displayed a slight but permanent increase and was on the average above 170 beats/min. A new arrangement of concepts for the anaerobic and aerobic-anaerobic threshold (as derived from energy metabolism) is suggested, that will make possible the determination of optimal work load intensities during endurance training by regulating heart rate.
In order to determine the ventilatory threshold (VT) and the lactate threshold (LT) in a reliable way, a new method is proposed and compared with conventional methods. The new method consists of calculating the point that yields the maximal distance from a curve representing ventilatory and metabolic variables as a function of oxygen uptake (VO2) to the line formed by the two end points of the curve (Dmax method). Male cyclists (n = 8) performed two incremental exercise tests a week apart. Ventilatory/metabolic variables were measured and blood was sampled for later lactate measurement during each workload and immediately after exercise. No statistical differences were observed in the threshold values (expressed as absolute oxygen uptake; VO2) determined by the Dmax method and the conventional linear regression method (according to O2 equivalent; EqO2) and venous blood at the onset of blood lactate (OBLA), while VT assessed with the conventional linear method (according to the slope of CO2 output; Vslope) yielded significantly lower threshold values. Similar results were obtained from the reproducibility test. Thus, the Dmax method appears to be an objective and reliable method for threshold determination, which can be applied to various ventilatory or metabolic variables yet yield similar results. The results also showed that breathing frequency can be used to determine VT.
The aim of the study was to examine whether the difference in lactate concentration in different blood fractions is of practical importance when using blood lactate as a test variable of aerobic endurance capacity. Ten male firefighters performed submaximally graded exercise on a cycle ergometer for 20-25 min. Venous and capillary blood samples were taken every 5 min for determination of haematocrit and lactate concentrations in plasma, venous and capillary blood. At the same time, expired air was collected in Douglas bags for determination of the oxygen consumption. A lactate concentration of 4.0 mmol.l-1 was used as the reference value to compare the oxygen consumption and exercise intensity when different types of blood specimen and sampling sites were used for lactate analysis. At this concentration the exercise intensity was 17% lower (P less than 0.01) when plasma lactate was compared to venous blood lactate, and 12% lower (P less than 0.05) when capillary blood lactate was used. Similar discrepancies were seen in oxygen consumption. The results illustrated the importance of standardizing sampling and handling of blood specimens for lactate determination to enable direct comparisons to be made among results obtained in different studies.