ArticlePDF Available

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

Authors:

## 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.
Content may be subject to copyright.
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
Science
&
Sports
(2012)
xxx,
xxx—xxx
Disponible
en
ligne
sur
www.sciencedirect.com
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
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
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. References [1] Monod H, Scherrer J. The work capacity of a synergic muscular group. Ergonomics 1965;8(3):329—38. [2] Moritani T, Nagata A, de Vries HA, Muro M. Critical power as a measure of physical work capacity and anaerobic threshold. Ergonomics 1981;24(5):339—50. [3] Poole DC, Ward SA, Gardner G, Whipp BJ. Metabolic and respi- ratory proﬁle of the upper limit for prolonged exercise in man. Ergonomics 1988;31(9):1265—79. [4] Poole DC, Ward SA, Whipp BJ. The effects of training on the metabolic and respiratory proﬁle of high-intensity cycle ergometer exercise. Eur J Appl Physiol 1990;59(6):421—9. [5] Billat VL, Mousele E, Roblot N, Melki J. Inter- and intra- strain variation in mouse critical running speed. J Appl Physiol 2005;98(4):1258—63. [6] Copp SW, Hirai DM, Musch TI, Poole DC. Critical speed in the rat: implications for hindlimb muscle blood ﬂow distribution and ﬁbre recruitment. J Physiol 2010;588(24):5077—87. [7] Hughson RL, Orok CJ, Staudt LE. A high-velocity treadmill run- ning test to assess endurance running potential. Int J Sports Med 1984;5(1):23—5. [8] Wakayoshi K, Ikuta K, Yoshida T, Udo M, Moritani T, Mutoh Y, et al. Determination and validity of critical velocity as an index of swimming performance in the competitive swimmer. Eur J Appl Physiol Occup Physiol 1992;64(2):153—7. [9] Hill DW, Alain C, Kennedy MD. Modeling the relationship between velocity and time to fatigue in rowing. Med Sci Sports Exerc 2003;35(12):2098—105. [10] Fukuba Y, Miura A, Endo M, Kan A, Yanagawa K, Whipp BJ. The curvature constant parameter of the power-duration curve for varied-power exercise. Med Sci Sports Exerc 2003;35(8):1413—8. [11] Hill DW, Poole DC, Smith JC. The relationship between power and time to achieve VO2max. Med Sci Sports Exerc 2002;34(4):709—14. [12] Brickley G, Doust J, Williams CA. Physiological responses dur- ing exercise to exhaustion at critical power. Eur J Appl Physiol 2002;88(1-2):146—51. [13] Carter H, Grice Y, Dekerle J, Brickley G, Hammond AJP, Pringle JS. Effect of prior exercise above and below criti- cal power on exercise to exhaustion. Med Sci Sports Exerc 2005;37(5):775—81. 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 6 R.D. de Lucas et al. [14] Bull AJ, Housh TJ, Johnson GO, Perry SR. Effect of mathemati- cal modeling on the estimation of critical power. Med Sci Sports Exerc 2000;32(2):526—30. [15] Bull AJ, Housh TJ, Johnson GO, Rana SR. Physiological responses at ﬁve estimates of critical velocity. Eur J Appl Physiol 2008;102(6):711—20. [16] Housh TJ, Cramer JT, Bull AJ, Johnson GO, Housh DJ. The effect of mathematical modeling on critical velocity. Eur J Appl Physiol 2001;84(5):469—75. [17] Dekerle J, Vanhatalo A, Burnley M. Determination of critical power from a single test. Sci Sports 2008;23(5):231—8. [18] Caputo F, Denadai BS. Does the 75% of the difference between the VO2at lactate threshold and VO2max lie at severe inten- sity domain in well trained cyclists? Sci Sports 2009;24(5): 257—61. [19] Carter H, Jones AM, Maxwell NS, Doust JH. The effect of inter- dian and diurnal variation on oxygen uptake kinetics during treadmill running. J Sports Sci 2002;20(11):901—9. [20] Davidson RCR, Corbett J, Ansley L. Inﬂuence of tempera- ture and protocol on the calibration of the computrainer electromagnetically braked cycling ergometer. J Sports Sci 2007;25(3):257—8. [21] Bentley DJ, Newell J, Bishop D. Incremental exercise test design and analysis: implications for performance diagnostics in endurance athletes. Sports Med 2007;37(7):575—86. [22] Lacour JR, Padilla-Magunacelaya S, Chatard JC, Arsac L, Barthelemy JC. Assessment of running velocity at maximal oxygen uptake. Eur J Appl Physiol Occup Physiol 1991;62(2): 77—82. [23] Kuipers H, Verstappen FT, Keizer HA, Geurten P, Van KG. Variability of aerobic performance in the laboratory and its physiologic correlates. Int J Sports Med 1985;6(4): 197—201. [24] Hill DW. The critical power concept. A review. Sports Med 1993;16(4):237—54. [25] Jenkins DG, Quigley BM. Blood lactate in trained cyclists during cycle ergometry at critical power. Eur J Appl Physiol Occup Physiol 1990;61(3—4):278—83. [26] Baron B, Dekerle J, Neviere R, Robin S, Pelayo P. Physiological responses during exercise performed to exhaustion at critical power. J Hum Mov Stud 2005;49:169—80. [27] Jones AM, Vanhatalo A, Burnley M, Morton RH, Poole DC. Crit- ical power: implications, for determination of VO2max and exercise tolerance. Med Sci Sports Exerc 2010;42(10):1876—90. [28] Burnley M, Doust JH, Vanhatalo A. A 3-min all-out test to deter- mine peak oxygen uptake and the maximal steady state. Med Sci Sports Exerc 2006;38(11):1995—2003. [29] Hill DW, Ferguson CS. A physiological description of critical velocity. Eur J Appl Physiol 1999;79(3):290—3. [30] Gaesser GA, Poole DC. The slow component of oxygen uptake kinetics in humans. Exerc Sport Sci Rev 1996;24:35—71. [31] Jones AM, Wilkerson DP, Dimenna F, Fulford J, Poole DC. Muscle metabolic responses to exercise above and below the ‘‘critical power’’ assessed using 31P-MRS. Am J Physiol Regul Integr Comp Physiol 2008;294(2):585—93. [32] Pringle JS, Jones AM. Maximal lactate steady state, crit- ical power and EMG during cycling. Eur J Appl Physiol 2002;88(3):214—26. [33] Dekerle J, Baron B, Dupont L, Vanvelcenaher J, Pelayo P. Max- imal lactate steady state, respiratory compensation threshold and critical power. Eur J Appl Physiol 2003;89(3—4):281—8. [34] Caritá RAC, Greco CC, Denadai BS. Máxima fase estável de lac- tato sanguíneo e potência crítica em ciclistas bem treinados. Rev Bras Med Esporte 2009;15(5):370—3. [35] Housh DJ, Housh TJ, Bauge SM. The accuracy of the criti- cal power test for predicting time to exhaustion during cycle ergometry. Ergonomics 1989;32(8):997—1004. [36] Gaesser GA, Carnevale TJ, Garﬁnkel A, Walter DO, Womack CJ. Estimation of critical power with nonlinear and linear models. Med Sci Sports Exerc 1995;27(10):1430—8. ... 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. ... Article Full-text available 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. ... Article Full-text available 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. ... Article Full-text available 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. ... Article Full-text available 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. Article Full-text available 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). Article Full-text available 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
Article
Full-text available
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.
Article
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.
Article
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.
Article
Full-text available
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.
Article
Full-text available
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.
Article
Full-text available
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.
Article
Full-text available