title: Differential effect of metabolic alkalosis and hypoxia on high-intensity cycling performance.
abstract: The purpose of this study was to investigate the effects of sodium bicarbonate (NaHCO3) ingestion and acute hypoxic exposure on repeated bouts of high-intensity cycling to task failure. Twelve subjects completed 4 separate intermittent cycling bouts cycling bouts to task failure (120% peak power output for 30-second interspersed with 30-second active recovery) under the following conditions: normoxia (FIO2% at 20.93%) alkalosis (NA), normoxia placebo (NP), hypoxia (FIO2% at 14.7%) alkalosis (HA), and hypoxia placebo (HP). For the NA and HA trials, the buffer solution (0.3 g·kg of NaHCO3) was dispensed into gelatin capsules and consumed over 90 minutes with 1 L of water. Whole-blood acid-base findings demonstrated metabolic alkalosis in both NA and HA before exercise (HCO3: 32.8 ± 1.8 mmol·L). Time to task failure was significantly impaired in the hypoxic conditions (NA: 199.1 ± 62.3 seconds, NP: 183.8 ± 45.0 seconds, HA: 127.8 ± 27.9 seconds, HP: 133.3 ± 28.7 seconds; p < 0.001; η = 0.7). There was no difference between the HA and HP conditions (p = 0.41); however the 2 normoxic conditions approached significance with the NA condition on average resulting in approximately 15-second improvement in time to task failure (p = 0.09). These findings suggest that an acute decline in FIO2% consistent with hypoxic exposure is more inhibiting than metabolic acidosis during intermittent high-intensity cycling to task failure. In application, the use of hypoxia and NaHCO3 concurrently to improve performance under these conditions does not seem warranted.
authors.affiliation: 1School of Science and Health, University of Western Sydney, Sydney, Australia; and 2New South Wales Institute of Sport (NSWIS), Sydney, Australia.
authors.forename: Samantha
authors.initials: S
authors.lastname: Flinn
authors.forename: Kathryn
authors.initials: K
authors.lastname: Herbert
authors.forename: Kenneth
authors.initials: K
authors.lastname: Graham
authors.forename: Jason C
authors.initials: JC
authors.lastname: Siegler
mesh_terms: D000328:Adult; D000471:Alkalosis / Q000503:physiopathology*; D002021:Buffers; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D064797:Physical Conditioning, Human / Q000379:methods / Q000502:physiology*; D017693:Sodium Bicarbonate / Q000008:administration & dosage*; D013997:Time Factors; D055815:Young Adult
chemical_list: D002021:Buffers; D017693:Sodium Bicarbonate