Determinants of curvature constant (W’) of the power duration relationship under normoxia and hypoxia: the effect of pre-exercise alkalosis

• DOI: 10.1007/s00421-017-3574-4
• Publication Date: 2017-03-09T14:17:23Z
• Authors: Sanjoy K. Deb; Lewis A. Gough; S. Andy Sparks; Lars R. McNaughton
• Keywords: Adult; Male; CAH02-06-02 - nutrition and dietetics; Exercise Tolerance; Anaerobic Threshold; RC1200 Sports Medicine; Public Health, Environmental and Occupational Health; 610; Alkalosis; CAH03-01-08 - molecular biology; 796; 3. Good health; CAH03-02-01 - sport and exercise sciences; 03 medical and health sciences; Oxygen Consumption; Sodium Bicarbonate; 0302 clinical medicine; CAH03-01-02 - biology (non-specific); Physiology (medical); Humans; Orthopedics and Sports Medicine; Original Article; Hypoxia; Exercise; biophysics and biochemistry

This study investigated the effect of induced alkalosis on the curvature constant (W') of the power-duration relationship under normoxic and hypoxic conditions.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-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). Pre-exercise administration of 0.3 g.kg-1 BM of NaHCO3 was used to induce alkalosis. Environmental conditions were set at either normobaric hypoxia (FiO2: 14.5%) or normoxia (FiO2: 20.93%).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).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 NaHCO3 increasing HCO3- buffering capacity to delay exercise-induced acidosis, which may, therefore, enhance anaerobic energy contribution.