Can measures of critical power precisely estimate the maximal metabolic steady-state?

Maturana, Felipe Mattioni; Keir, Daniel A.; McLay, Kaitlin M.; Murias, Juan M.

doi:10.1139/apnm-2016-0248

Cited by 60 publications

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“…Despite the difference in bias, the dispersion of the data was remarkably similar in both studies (the 95% confidence interval was 54 W vs 61 W, respectively), indicating that the error associated with the estimate of CP was consistently high and that model parameter estimates were not accurate in approximating the "true" CP. We also demonstrated that the CP estimated from traditional modelling methods and the 3-min all-out test (Burnley et al 2006) differed in many participants by more than 30 W (this despite similar group mean power outputs), indicating large intra-individual variability between methods (Mattioni Maturana et al 2016). Furthermore, using blood lactate-based experimental verification of CP, we recently demonstrated that young healthy individuals were capable of self-selecting their CP with greater accuracy than traditional methods (Mattioni Maturana et al 2017).…”

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confidence: 78%

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Keir

Maturana

Murias

2018

Appl. Physiol. Nutr. Metab.

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In his editorial, de Lucas (2018) indicates that the coherence between the intensities corresponding to maximal lactate steadystate (MLSS) and critical power (CP) is dependent on the methods and model used to determine CP. While there is no question that different mathematical models applied to power-time series datasets of varying time limits can produce different CP values, we completely disagree that this refutes an equivalence between these 2 constructs. CP is not a variable that is dependent on power output and time to exhaustion; rather, it is a parameter that contributes to determining how long one can sustain a given power output! The CP concept is predicated on the hyperbolic relationship that exists between exercise intensity and tolerable duration at that constant intensity (Monod and Scherrer 1965). From a mathematical standpoint, such a relationship implies that exercise performed constantly at the asymptotic intensity should be tolerated indefinitely. From a physiological perspective, we know that this intensity cannot be sustained "indefinitely" because other factors (e.g., substrate depletion, muscle fatigue, hyperthermia, motivation, etc.) inevitably intervene to determine tolerable duration. The discord between the mathematical and physiological constructs that predict respectively "infinite" versus "finite" exercise tolerance at CP has contributed to its notoriously ambiguous definition as "the highest intensity that can be sustained for a prolonged time". However, in our view, acceptance as true of the CP output from a mathematical model applied to a power-time series dataset (without verification) is the main obfuscator of what CP truly represents.In his letter, de Lucas, like many others, neglects to acknowledge the appropriate precedence that links the mathematical CP model to distinct underlying physiology. Poole et al. (1988) were among the first to identify CP as the highest intensity above which respiratory and metabolic measures (which included blood lactate) may no longer achieve steady-state. Since this seminal study, CP has been verified to demarcate an intensity above which oxygen uptake, blood and muscle lactate and hydrogen ion concentration, intramuscular phosphocreatine, and inorganic phosphate may no longer be stabilized (e.g., Jones et al. 2008;Black et al. 2017). Collectively, these studies expanded the colloquial definition of CP to "the highest intensity that can be sustained for a prolonged time solely by oxidative energy provision". An important caveat of this expanded definition is that exercise at CP does not draw upon anaerobic metabolism and therefore progressive depletions in phosphocreatine and progressive accumulations of lactate in muscle and blood are not evident with time. Presumably, this minimizes metabolic and acid-base disturbance and reduces (or delays) the initiation of fatigue processes -prolonging exercise tolerance. Therefore, the physiological response expected at CP encompasses the concept of MLSS; any differences observed between these 2 interdepe...

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confidence: 78%

“…de Lucas also correctly points out a discrepancy between the results of Keir et al (2015) andMattioni Maturana et al (2016). That is, the 3-parameter hyperbolically derived CP was shown to approximate (mean bias = −2 W, p > 0.05) and overestimate (mean bias = 19 W, p < 0.05) the MLSS in 2 different sample groups, respectively.…”

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Reply to “Discussion of ‘Can measures of critical power precisely estimate the maximal metabolic steady-state?’ – Is it still necessary to compare critical power to maximal lactate steady state?” – When is it appropriate to compare critical power to maximal lactate steady-state?

Keir

Maturana

Murias

2018

Appl. Physiol. Nutr. Metab.

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“…I read with great interest the study of Mattioni Maturana et al (2016), which was published in Applied Physiology, Nutrition, and Metabolism. However, I wish to raise some concerns regarding this study, especially considering 2 other studies from the same research group (Keir et al 2015;Mattioni Maturana et al 2017).…”

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confidence: 99%

“…The answer is: it depends! In general terms, the aforementioned studies (Keir et al 2015;Mattioni Maturana et al 2016, 2017, which aimed to compare CP and MLSS, have used different criteria to set CP, providing divergent conclusions.…”

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confidence: 99%

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Discussion of “Can measures of critical power precisely estimate the maximal metabolic steady-state?” – Is it still necessary to compare critical power to maximal lactate steady state?

Lucas

2018

Appl. Physiol. Nutr. Metab.

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Steady-state $$\dot{V}{\text{O}}_{2}$$ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners

et al. 2021

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The metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 was stable over time from speeds at which a steady-state $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 could not be established. Ten well-trained male distance runners completed 9–12 constant-speed treadmill tests, including 3–5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P < 0.001). Blood lactate concentration was higher and increased with time at a speed 0.5 km/h higher than MLSS compared to MLSS (P < 0.01); however, pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 did not change significantly between 10 and 30 min at either MLSS or MLSS + 0.5 km/h. In contrast, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 increased significantly over time and reached $$\dot{V}{\text{O}}_{2\,\,\max }$$ V ˙ O 2 max at end-exercise at a speed ~ 0.4 km/h above CS (P < 0.05) but remained stable at a speed ~ 0.5 km/h below CS. The stability of $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 at a speed exceeding MLSS suggests that MLSS underestimates the maximal metabolic steady state. These results indicate that CS more closely represents the maximal metabolic steady state when the latter is appropriately defined according to the ability to stabilise pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 .

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Can measures of critical power precisely estimate the maximal metabolic steady-state?

Cited by 60 publications

References 43 publications

Reply to “Discussion of ‘Can measures of critical power precisely estimate the maximal metabolic steady-state?’ – Is it still necessary to compare critical power to maximal lactate steady state?” – When is it appropriate to compare critical power to maximal lactate steady-state?

Reply to “Discussion of ‘Can measures of critical power precisely estimate the maximal metabolic steady-state?’ – Is it still necessary to compare critical power to maximal lactate steady state?” – When is it appropriate to compare critical power to maximal lactate steady-state?

Discussion of “Can measures of critical power precisely estimate the maximal metabolic steady-state?” – Is it still necessary to compare critical power to maximal lactate steady state?

Steady-state $$\dot{V}{\text{O}}_{2}$$ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners

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