Determinants of curvature constant (W') of the power duration relationship under normoxia and hypoxia: the effect of preexercise alkalosis

Deb A Sanjoy, Lewis Gough, Andy Sparks, Lars McNaughton

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13 Citations (Scopus)
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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 yrs; 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.g. normoxia and hypoxia) and four x 3 min critical power (CP) tests under different experimental conditions. Participants completed four trials: alkalosis normoxia (ALN); placebo normoxia (PLN); alkalosis hypoxia (ALH); and placebo hypoxia (PLH). Preexercise administration of 0.3 BM of NaHCO3 was used to induce alkalosis. Environmental conditions were set at either normobaric hypoxia (FiO2: 14.5%) or normoxia (FiO2: 20.93%). Results: An increase in W' was observed with preexercise alkalosis under both normoxic (PLN: 15.1 ± 6.2 kJ vs. ALN: 17.4 ± 5.1 kJ; P = 0.006) and hypoxic conditions (ALN: 15.2 ± 4.9 kJ vs. ALN: 17.9 ± 5.2 kJ; P < 0.001). Preexercise alkalosis resulted in a larger reduction in bicarbonate ion (HCO3-) concentrations during exercise in both environmental conditions (p < 0.001) and a greater blood lactate accumulation under hypoxia (P = 0.012). Conclusion: Preexercise alkalosis substantially increased W', and therefore may determine tolerance to exercise above CP under normoxic and hypoxic conditions. This may be due to NaHCO3 increasing HCO3- buffering capacity to delay exercise-induced acidosis, which may therefore enhance anaerobic energy contribution.
Original languageEnglish
Pages (from-to)901-912
JournalEuropean Journal of Applied Physiology
Issue number5
Early online date9 Mar 2017
Publication statusE-pub ahead of print - 9 Mar 2017


  • critical power
  • sodium bicarbonate
  • altitude
  • severe intensity domain

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