Exercise Intensity Thresholds: Identifying the Boundaries of Sustainable Performance.

Autor:	Keir DA; 1Canadian Centre for Activity and Aging, University of Western Ontario, London, Ontario, CANADA; 2School of Kinesiology, University of Western Ontario, London, Ontario, CANADA; 3Department of Neurological and Movement Sciences, University of Verona, Verona, ITALY; 4Faculty of Kinesiology, University of Calgary, Calgary, Alberta, CANADA; and 5Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, CANADA., Fontana FY, Robertson TC, Murias JM, Paterson DH, Kowalchuk JM, Pogliaghi S
Jazyk:	angličtina
Zdroj:	Medicine and science in sports and exercise [Med Sci Sports Exerc] 2015 Sep; Vol. 47 (9), pp. 1932-40.
DOI:	10.1249/MSS.0000000000000613
Abstrakt:	Unlabelled: Critical power (CP), respiratory compensation point (RCP), maximal lactate steady state (MLSS), and deoxyhemoglobin breakpoint ([HHb]BP) are alternative functional indices that are thought to demarcate the highest exercise intensity that can be tolerated for long durations. Purpose: We tested the hypothesis that CP, RCP, MLSS, and [HHb]BP occur at the same metabolic intensity by examining the pulmonary oxygen uptake (V˙)O2p and power output (PO) associated with each "threshold." Methods: Twelve healthy men (mean ± SD age, 27 ± 3 yr) performed the following tests on a cycle ergometer: i) four to five exhaustive tests for determination of CP, ii) two to three 30-min constant-power trials for MLSS determination, and iii) a ramp incremental exercise test from which the V˙O2p and PO at RCP and [HHb]BP were determined. During each trial, breath-by-breath V˙O2p and ventilatory variables were measured with a metabolic cart and flowmeter turbine; near-infrared spectroscopy-derived [HHb] was monitored using a frequency domain multidistance system, and arterialized capillary blood lactate was sampled at regular intervals. Results: There were no differences (P > 0.05) among the V˙O2p values associated with CP, RCP, MLSS, and [HHb]BP (CP, 3.29 ± 0.48; RCP, 3.34 ± 0.45; MLSS, 3.27 ± 0.44; [HHb]BP, 3.41 ± 0.46 L·min(-1)); however, the PO associated with RCP (262 ± 48 W) and [HHb]BP (273 ± 41 W) were greater (P < 0.05) than both CP (226 ± 45 W) and MLSS (223 ± 39 W), which, themselves, were not different (P > 0.05). Conclusions: Although the standard methods for determination of CP, RCP, MLSS, and [HHb]BP are different, these indices occur at the same V˙O2p, suggesting that i) they may manifest as a result of similar physiological phenomenon and ii) each provides a valid delineation between tolerable and intolerable constant-power exercise.
Databáze:	MEDLINE
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