Differential effect of metabolic alkalosis and hypoxia on high-intensity cycling performance

Samantha Flinn, Kathryn Herbert, Kenneth Graham, Jason C. Siegler

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


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-1 of NaHCO3) was dispensed into gelatin capsules and consumed over 90 minutes with 1 L of water. Whole-blood acidbase findings demonstrated metabolic alkalosis in both NA and HA before exercise (HCO3-: 32.8 ± 1.8 mmol·L-1). 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; η2 = 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 highintensity cycling to task failure. In application, the use of hypoxia and NaHCO3 concurrently to improve performance under these conditions does not seem warranted.

Original languageEnglish (US)
Pages (from-to)2852-2858
Number of pages7
JournalJournal of Strength and Conditioning Research
Issue number10
StatePublished - Oct 1 2014
Externally publishedYes


  • Altitude
  • Buffering
  • Intermittent hypoxic training
  • Sodium bicarbonate

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation


Dive into the research topics of 'Differential effect of metabolic alkalosis and hypoxia on high-intensity cycling performance'. Together they form a unique fingerprint.

Cite this