title: Determinants of curvature constant (W') of the power duration relationship under normoxia and hypoxia: the effect of pre-exercise alkalosis.
abstract: OBJECTIVE
  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-1completed 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). Pre-exercise administration of 0.3 g.kg-1BM of NaHCO3was 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 pre-exercise 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). Pre-exercise 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).
  
  
  CONCLUSIONS
  Pre-exercise alkalosis substantially increased W' and, therefore, may determine tolerance to exercise above CP under normoxic and hypoxic conditions. This may be due to NaHCO3increasing HCO3-buffering capacity to delay exercise-induced acidosis, which may, therefore, enhance anaerobic energy contribution.
authors.affiliation: Department of Sport and Physical Activity, Edge Hill University, St Helen's Road, Ormskirk, L39 4QP, UK.
authors.forename: Sanjoy K
authors.initials: SK
authors.lastname: Deb
authors.affiliation: Department of Sport and Physical Activity, Edge Hill University, St Helen's Road, Ormskirk, L39 4QP, UK.
authors.forename: Lewis A
authors.initials: LA
authors.lastname: Gough
authors.affiliation: Department of Sport and Physical Activity, Edge Hill University, St Helen's Road, Ormskirk, L39 4QP, UK.
authors.forename: S Andy
authors.initials: SA
authors.lastname: Sparks
authors.affiliation: Department of Sport and Physical Activity, Edge Hill University, St Helen's Road, Ormskirk, L39 4QP, UK. lars.mcnaughton@edgehill.ac.uk.
authors.forename: Lars R
authors.initials: LR
authors.lastname: McNaughton
mesh_terms: D000328:Adult; D000471:Alkalosis / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D015308:Anaerobic Threshold; D015444:Exercise; D017079:Exercise Tolerance; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D010101:Oxygen Consumption; D017693:Sodium Bicarbonate / Q000009:adverse effects
chemical_list: D017693:Sodium Bicarbonate
keywords: Altitude; Critical power; Severe intensity domain; Sodium bicarbonate