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  • Title: Exercise intolerance at high altitude (5050 m): critical power and W'.
    Author: Valli G, Cogo A, Passino C, Bonardi D, Morici G, Fasano V, Agnesi M, Bernardi L, Ferrazza AM, Ward SA, Palange P.
    Journal: Respir Physiol Neurobiol; 2011 Aug 15; 177(3):333-41. PubMed ID: 21621651.
    Abstract:
    The relationship between work rate (WR) and its tolerable duration (t(LIM)) has not been investigated at high altitude (HA). At HA (5050 m) and at sea level (SL), six subjects therefore performed symptom-limited cycle-ergometry: an incremental test (IET) and three constant-WR tests (% of IET WR(max), HA and SL respectively: WR(1) 70±8%, 74±7%; WR(2) 86±14%, 88±10%; WR(3) 105±13%, 104±9%). The power asymptote (CP) and curvature constant (W') of the hyperbolic WR-t(LIM) relationship were reduced at HA compared to SL (CP: 81±21 vs. 123±38 W; W': 7.2±2.9 vs. 13.1±4.3 kJ). HA breathing reserve (estimated maximum voluntary ventilation minus end-exercise ventilation) was also compromised (WR(1): 25±25 vs. 50±18 l min(-1); WR(2): 4±23 vs. 38±23 l min(-1); WR(3): -3±18 vs. 32±24 l min(-1)) with near-maximal dyspnea levels (Borg) (WR(1): 7.2±1.2 vs. 4.8±1.3; WR(2): 8.8±0.8 vs. 5.3±1.2; WR(3): 9.3±1.0 vs. 5.3±1.5). The CP reduction is consistent with a reduced O(2) availability; that of W' with reduced muscle-venous O(2) storage, exacerbated by ventilatory limitation and dyspnea.
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