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"Critical power"

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https://www.readbyqxmd.com/read/28437928/terahertz-optical-bistability-of-graphene-in-thin-layers-of-dielectrics
#1
Kwang Jun Ahn, Fabian Rotermund
We theoretically studied in terahertz frequency regime optical bistability of graphene placed at the interface between thin dielectric layers. We solved self-consistently the nonlinear wave equations containing the third-order optical conductivity of graphene in four-layer structures and obtained hysteresis response of the transmitted power as a function of the incident power. We numerically observed that the critical powers for the up and down transitions and the Fermi-energy of graphene required for terahertz optical bistability can be reduced by carefully choosing material properties and the thicknesses of dielectric layers...
April 17, 2017: Optics Express
https://www.readbyqxmd.com/read/28388783/the-reliability-and-validity-of-the-3-min-all-out-cycling-critical-power-test
#2
James Wright, Stewart Bruce-Low, Simon A Jobson
Research suggests that critical power (CP) can be estimated from a single 3-min bout of all-out cycling. The purpose of this study was to investigate the reliability and validity of the 3-min all-out cycling test when carried out at a constant cadence (isokinetic) and against a fixed resistance (linear). 12 participants completed 8 tests: 1) a ramp test; 2-4) 3 fixed power tests to calculate CP and W' using the 1/time mathematical model; 5-8) four 3-min all-out tests to calculate EP and WEP; 2 isokinetic and 2 linear tests...
April 7, 2017: International Journal of Sports Medicine
https://www.readbyqxmd.com/read/28386237/prediction-of-critical-power-and-w-in-hypoxia-application-to-work-balance-modelling
#3
Nathan E Townsend, David S Nichols, Philip F Skiba, Sebastien Racinais, Julien D Périard
Purpose: Develop a prediction equation for critical power (CP) and work above CP (W') in hypoxia for use in the work-balance ([Formula: see text]) model. Methods: Nine trained male cyclists completed cycling time trials (TT; 12, 7, and 3 min) to determine CP and W' at five altitudes (250, 1,250, 2,250, 3,250, and 4,250 m). Least squares regression was used to predict CP and W' at altitude. A high-intensity intermittent test (HIIT) was performed at 250 and 2,250 m. Actual and predicted CP and W' were used to compute W' during HIIT using differential ([Formula: see text]) and integral ([Formula: see text]) forms of the [Formula: see text] model...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28367980/power-scalable-subcycle-pulses-from-laser-filaments
#4
A A Voronin, A M Zheltikov
Compression of optical pulses to ultrashort pulse widths using methods of nonlinear optics is a well-established technology of modern laser science. Extending these methods to pulses with high peak powers, which become available due to the rapid progress of laser technologies, is, however, limited by the universal physical principles. With the ratio P/Pcr of the peak power of an ultrashort laser pulse, P, to the critical power of self-focusing, Pcr, playing the role of the fundamental number-of-particles integral of motion of the nonlinear Schrödinger equation, keeping this ratio constant is a key principle for the power scaling of laser-induced filamentation...
April 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28332113/the-critical-power-concept-applications-to-sports-performance-with-a-focus-on-intermittent-high-intensity-exercise
#5
REVIEW
Andrew M Jones, Anni Vanhatalo
The curvilinear relationship between power output and the time for which it can be sustained is a fundamental and well-known feature of high-intensity exercise performance. This relationship 'levels off' at a 'critical power' (CP) that separates power outputs that can be sustained with stable values of, for example, muscle phosphocreatine, blood lactate, and pulmonary oxygen uptake ([Formula: see text]), from power outputs where these variables change continuously with time until their respective minimum and maximum values are reached and exercise intolerance occurs...
March 2017: Sports Medicine
https://www.readbyqxmd.com/read/28302463/critical-power-testing-or-self-selected-cycling-which-one-is-the-best-predictor-of-maximal-metabolic-steady-state
#6
Felipe Mattioni Maturana, Daniel A Keir, Kaitlin M McLay, Juan M Murias
Critical power (CP) demarcates the boundary between heavy and very heavy exercise intensity domains, and therefore, the power output (PO) that can be sustained at the maximal metabolic steady-state during constant-PO exercise (i.e., maximal lactate steady-state (MLSS)). However, the estimated CP does not always reflect a sustainable intensity of exercise, where blood lactate concentration ([La]) and oxygen uptake (V˙O2) reach a plateau. OBJECTIVES: To test cyclists' ability to predict their highest PO associated with metabolic steady-state based on their own perception of effort...
January 24, 2017: Journal of Science and Medicine in Sport
https://www.readbyqxmd.com/read/28280973/determinants-of-curvature-constant-w-of-the-power-duration-relationship-under-normoxia-and-hypoxia-the-effect-of-pre-exercise-alkalosis
#7
Sanjoy K Deb, Lewis A Gough, S Andy Sparks, Lars R McNaughton
PURPOSE: This study investigated the effect of induced alkalosis on the curvature constant (W') of the power-duration relationship under normoxic and hypoxic conditions. METHODS: Eleven trained cyclists (mean ± SD) Age: 32 ± 7.2 years; body mass (bm): 77.0 ± 9.2 kg; VO2peak: 59.2 ± 6.8 ml·kg(-1)·min(-1) completed seven laboratory visits which involved the determination of individual time to peak alkalosis following sodium bicarbonate (NaHCO3) ingestion, an environment specific ramp test (e...
March 9, 2017: European Journal of Applied Physiology
https://www.readbyqxmd.com/read/28166117/the-respiratory-compensation-point-is-not-a-valid-surrogate-for-critical-power
#8
Jeffrey A Leo, Surendran Sabapathy, Michael J Simmonds, Troy J Cross
PURPOSE: It is unclear whether the respiratory compensation point (RCP) may be used as a valid surrogate for critical power (CP). Accordingly, we sought to determine the measurement agreement between CP and the RCP obtained during incremental cycling of varying ramp slopes. METHODS: Eleven recreationally-active men completed three separate ramp-incremental cycling protocols, where the work rate increment was slow (SR: 15 W[BULLET OPERATOR]min), medium (MR: 30 W[BULLET OPERATOR]min) or fast (FR: 45 W[BULLET OPERATOR]min)...
February 4, 2017: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/28019724/a-comparison-of-methods-to-estimate-anaerobic-capacity-accumulated-oxygen-deficit-and-w-during-constant-and-all-out-work-rate-profiles
#9
Daniel Muniz-Pumares, Charles Pedlar, Richard Godfrey, Mark Glaister
This study investigated (i) whether the accumulated oxygen deficit (AOD) and curvature constant of the power-duration relationship (W') are different during constant work-rate to exhaustion (CWR) and 3-min all-out (3MT) tests and (ii) the relationship between AOD and W' during CWR and 3MT. Twenty-one male cyclists (age: 40 ± 6 years; maximal oxygen uptake [V̇O2max]: 58 ± 7 ml · kg(-1) · min(-1)) completed preliminary tests to determine the V̇O2-power output relationship and V̇O2max. Subsequently, AOD and W' were determined as the difference between oxygen demand and oxygen uptake and work completed above critical power, respectively, in CWR and 3MT...
December 26, 2016: Journal of Sports Sciences
https://www.readbyqxmd.com/read/28008101/muscle-metabolic-and-neuromuscular-determinants-of-fatigue-during-cycling-in-different-exercise-intensity-domains
#10
Matthew I Black, Andrew M Jones, Jamie R Blackwell, Stephen J Bailey, Lee J Wylie, Sinead T J McDonagh, Christopher Thompson, James Kelly, Paul Sumners, Katya J Mileva, Joanna L Bowtell, Anni Vanhatalo
The lactate or gas exchange threshold (GET) and the critical power (CP) are closely associated with human exercise performance. We tested the hypothesis that the limit of tolerance (Tlim) during cycle exercise performed within the exercise intensity domains demarcated by GET and CP is linked to discrete muscle metabolic and neuromuscular responses. Eleven males performed a ramp incremental exercise test, 4-5 severe-intensity (SEV; >CP) constant-work-rate (CWR) tests until Tlim, a heavy-intensity (HVY; <CP but >GET) CWR test until Tlim, and a moderate-intensity (MOD; <GET) CWR test until Tlim Muscle biopsies revealed that a similar (P>0...
December 22, 2016: Journal of Applied Physiology
https://www.readbyqxmd.com/read/27991483/differing-six-minute-pacing-strategies-effect-anaerobic-contribution-oxygen-uptake-muscle-deoxygenation-and-cycle-performance
#11
John Murray, Michael McCrudden, Juan M Murias, Volker Nolte, Glen R Belfry
BACKGROUND: This study compared an all-out start (AO) to a constant power start strategy (CON) during a 6 min cycle performance on utilization of W ́ (energy above critical power (CP)), muscle deoxygenation (HHb), oxygen uptake (VO2) and performance in recreationally active individuals. The AO strategy was similar to that employed by rowers. METHODS: Eight healthy males (age = 24 ± 3 y) completed a ramp test to fatigue (VO2peak = 4.42 ± 0.54 L∙min-1; peak power = 385 ± 35 W) and a 3-min all-out test to determine CP and the CON work rate...
December 16, 2016: Journal of Sports Medicine and Physical Fitness
https://www.readbyqxmd.com/read/27918663/comparison-of-critical-power-and-w-derived-from-two-or-three-maximal-tests
#12
Len Parker Simpson, Mehdi Kordi
PURPOSE: Typically, accessing the asymptote (Critical Power; CP) and curvature constant (W') parameters of the hyperbolic power-duration relationship requires multiple constant-power, exhaustive exercise trials, spread over several visits. However, more recently single-visit protocols and personal power meters have been used. We investigated the practicality of using a two-trial, single-visit protocol in providing reliable CP & W' estimates. METHODS: 8 trained cyclists underwent 3- and 12-min maximal exercise trials in a single session to derive (2-trial) CP & W' estimates...
December 5, 2016: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/27834562/predicting-critical-power-in-elite-cyclists-questioning-validity-of-the-3-min-all-out-test
#13
Jason C Bartram, Dominic Thewlis, David T Martin, Kevin I Norton
PURPOSE: New applications of the critical power concept, such as the modelling of intermittent work capabilities, are exciting prospects for elite cycling. However, accurate calculation of the required parameters is traditionally time invasive and somewhat impractical. An alternative single test protocol (3-min All-out) has recently been proposed, but validation in an elite population is lacking. The traditional approach for parameter establishment, but with fewer tests, could also prove an acceptable compromise...
November 11, 2016: International Journal of Sports Physiology and Performance
https://www.readbyqxmd.com/read/27819154/can-measures-of-critical-power-precisely-estimate-the-maximal-metabolic-steady-state
#14
COMPARATIVE STUDY
Felipe Mattioni Maturana, Daniel A Keir, Kaitlin M McLay, Juan M Murias
Critical power (CP) conceptually represents the highest power output (PO) at physiological steady-state. In cycling exercise, CP is traditionally derived from the hyperbolic relationship of ∼5 time-to-exhaustion trials (TTE) (CPHYP). Recently, a 3-min all-out test (CP3MIN) has been proposed for estimation of CP as well the maximal lactate steady-state (MLSS). The aim of this study was to compare the POs derived from CPHYP, CP3MIN, and MLSS, and the oxygen uptake and blood lactate concentrations at MLSS. Thirteen healthy young subjects (age, 26 ± 3years; mass, 69...
November 2016: Applied Physiology, Nutrition, and Metabolism, Physiologie Appliquée, Nutrition et Métabolisme
https://www.readbyqxmd.com/read/27806677/power-duration-relationship-physiology-fatigue-and-the-limits-of-human-performance
#15
Mark Burnley, Andrew M Jones
The duration that exercise can be maintained decreases as the power requirements increase. In this review, we describe the power-duration (PD) relationship across the full range of attainable power outputs in humans. We show that a remarkably small range of power outputs is sustainable (power outputs below the critical power, CP). We also show that the origin of neuromuscular fatigue differs considerably depending on the exercise intensity domain in which exercise is performed. In the moderate domain (below the lactate threshold, LT), fatigue develops slowly and is predominantly of central origin (residing in the central nervous system)...
November 3, 2016: European Journal of Sport Science
https://www.readbyqxmd.com/read/27787608/the-constant-work-rate-critical-power-protocol-overestimates-ramp-incremental-exercise-performance
#16
Matthew I Black, Andrew M Jones, James A Kelly, Stephen J Bailey, Anni Vanhatalo
PURPOSE: The parameters of the power-duration relationship (i.e., the critical power, CP, and the curvature constant, W') may theoretically predict maximal performance capability for exercise above the CP. The CP and W' are associated with the parameters of oxygen uptake ([Formula: see text]O2) kinetics, which can be altered by manipulation of the work-rate forcing function. We tested the hypothesis that the CP and W' derived from constant work-rate (CWR) prediction trials would overestimate ramp incremental exercise performance...
December 2016: European Journal of Applied Physiology
https://www.readbyqxmd.com/read/27782419/structure-and-dynamics-of-binary-liquid-mixtures-near-their-continuous-demixing-transitions
#17
Sutapa Roy, S Dietrich, Felix Höfling
The dynamic and static critical behavior of a family of binary Lennard-Jones liquid mixtures, close to their continuous demixing points (belonging to the so-called model H' dynamic universality class), are studied computationally by combining semi-grand canonical Monte Carlo simulations and large-scale molecular dynamics (MD) simulations, accelerated by graphic processing units (GPU). The symmetric binary liquid mixtures considered cover a variety of densities, a wide range of compressibilities, and various interactions between the unlike particles...
October 7, 2016: Journal of Chemical Physics
https://www.readbyqxmd.com/read/27688431/w-expenditure-and-reconstitution-during-severe-intensity-constant-power-exercise-mechanistic-insight-into-the-determinants-of-w
#18
Ryan M Broxterman, Phillip F Skiba, Jesse C Craig, Samuel L Wilcox, Carl J Ade, Thomas J Barstow
The sustainable duration of severe intensity exercise is well-predicted by critical power (CP) and the curvature constant (W'). The development of the W'BAL model allows for the pattern of W' expenditure and reconstitution to be characterized and this model has been applied to intermittent exercise protocols. The purpose of this investigation was to assess the influence of relaxation phase duration and exercise intensity on W' reconstitution during dynamic constant power severe intensity exercise. Six men (24...
October 2016: Physiological Reports
https://www.readbyqxmd.com/read/27686573/knowledge-is-power-issues-of-measuring-training-and-performance-in-cycling
#19
L Passfield, J G Hopker, S Jobson, D Friel, M Zabala
Mobile power meters provide a valid means of measuring cyclists' power output in the field. These field measurements can be performed with very good accuracy and reliability making the power meter a useful tool for monitoring and evaluating training and race demands. This review presents power meter data from a Grand Tour cyclist's training and racing and explores the inherent complications created by its stochastic nature. Simple summary methods cannot reflect a session's variable distribution of power output or indicate its likely metabolic stress...
July 2017: Journal of Sports Sciences
https://www.readbyqxmd.com/read/27613650/an-integrated-view-on-the-oxygenation-responses-to-incremental-exercise-at-the-brain-the-locomotor-and-respiratory-muscles
#20
REVIEW
Jan Boone, Kristof Vandekerckhove, Ilse Coomans, Fabrice Prieur, Jan G Bourgois
In the past two decades oxygenation responses to incremental ramp exercise, measured non-invasively by means of near-infrared spectroscopy at different locations in the body, have advanced the insights on the underpinning mechanisms of the whole-body pulmonary oxygen uptake ([Formula: see text]) response. In healthy subjects the complex oxygenation responses at the level of locomotor and respiratory muscles, and brain were simplified and quantified by the detection of breakpoints as a deviation in the ongoing response pattern as work rate increases...
December 2016: European Journal of Applied Physiology
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