| Pulmonary O2 uptake kinetics as a determinant of high-intensity exercise tolerance in humans. | |
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MedLine Citation:
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PMID: 21415174 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Tolerance to high-intensity constant-power (P) exercise is well described by a hyperbola with two parameters: a curvature constant (W') and power asymptote termed 'critical power' (CP). Since the ability to sustain exercise is closely related to the ability to meet the ATP demand in a steady state, we reasoned that pulmonary O(2) uptake (VO(2)) kinetics would relate to the P-t(lim) parameters. We hypothesized that: 1) the fundamental time-constant (τVO(2)) would relate inversely to CP; and 2) the slow-component magnitude (ΔVO(2sc)) would relate directly to W'. Fourteen healthy men performed cycle ergometry protocols to the limit of tolerance: i) an incremental-ramp test; ii) a series of constant-P tests to determine VO(2max), CP and W'; and iii) repeated constant-P tests (WR(6)) normalized to a 6-min tolerable duration (t(lim)) for τVO(2) and ΔVO(2sc) estimation. The WR(6) t(lim) averaged 365±16s and VO(2max) (4.18±0.49L.min(-1)) was achieved in every case. CP (range: 171-294W) was inversely correlated with τVO(2) (18-38s; R(2)=0.90), and W' (12.8-29.9kJ) was directly correlated with ΔVO(2sc) (0.42-0.96L.min(-1); R(2)=0.76). These findings support the notions that: 1) rapid VO(2) adaptation at exercise onset allows a steady state to be achieved at higher work rates compared to when VO(2) kinetics are slower; and 2) exercise exceeding this limit initiates a 'fatigue cascade' linking W' to a progressive increase in the O(2)-cost of power production (VO(2sc)), which, if continued, results in the attainment of VO(2max) and exercise intolerance. Collectively, these data implicate VO(2) kinetics as a key determinant of high-intensity exercise tolerance in humans. |
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Authors:
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Scott R Murgatroyd; Carrie Ferguson; Susan A Ward; Brian James Whipp; Harry B Rossiter |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-3-17 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: - ISSN: 1522-1601 ISO Abbreviation: - Publication Date: 2011 Mar |
Date Detail:
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Created Date: 2011-3-18 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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1University of Leeds. |
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