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

Deb, S., Gough, L., Sparks, S.A. and McNaughton, L. 2017. Determinants of curvature constant (W’) of the power duration relationship under normoxia and hypoxia: the effect of pre-exercise alkalosis. European Journal of Applied Physiology. 117 (5), pp. 901-912. doi:10.1007/s00421-017-3574-4

TitleDeterminants of curvature constant (W’) of the power duration relationship under normoxia and hypoxia: the effect of pre-exercise alkalosis
TypeJournal article
AuthorsDeb, S., Gough, L., Sparks, S.A. and McNaughton, L.
Abstract

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 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%).

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).

Conclusion

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.

Keywordscritical power, sodium bicarbonate, altitude, severe intensity domain
JournalEuropean Journal of Applied Physiology
Journal citation117 (5), pp. 901-912
ISSN1439-6319
Year2017
PublisherSpringer
Digital Object Identifier (DOI)doi:10.1007/s00421-017-3574-4
Publication dates
Published online09 Mar 2017
Published in printMay 2017

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