TY - JOUR
T1 - Sodium bicarbonate ingestion alters the slow but not the fast phase of V̇O2 kinetics
AU - Berger, Nicolas
AU - Mcnaughton, Lars R.
AU - Keatley, Simon
AU - Wilkerson, Daryl P.
AU - Jones, Andrew M.
PY - 2006/11/1
Y1 - 2006/11/1
N2 - Purpose: The influence of metabolic alkalosis (ALK) on pulmonary O 2 uptake (pV̇O2) kinetics during high-intensity cycle exercise is controversial. The purpose of this study was to examine the influence of ALK induced by sodium bicarbonate (NaHCO3) ingestion on pV̇O2 kinetics, using a sufficient number of repeat-step transitions to provide high confidence in the results obtained. Methods: Seven healthy males completed step tests to a work rate requiring 80% pV̇O 2max on six separate occasions: three times after ingestion of 0.3 g·kg-1 body mass NaHCO3 in 1 L of fluid, and three times after ingestion of a placebo (CON). Blood samples were taken to assess changes in acid-base balance, and pV̇O2 was measured breath-by-breath. Results: NaHCO3 ingestion significantly increased blood pH and [bicarbonate] both before and during exercise relative to the control condition (P < 0.001). The time constant of the phase II pV̇O2 response was not different between conditions (CON: 29 ± 6 vs ALK: 32 ± 7 s; P = 0.21). However, the onset of the pV̇O2 slow component was delayed by NaHCO3 ingestion (CON: 120 ± 19 vs ALK: 147 ± 34 s; P < 0.01), resulting in a significantly reduced end-exercise pV̇O2 (CON: 2.88 ± 0.19 vs ALK: 2.79 ± 0.23 L-min-1; P < 0.05). Conclusions: Metabolic alkalosis has no effect on phase II pV̇O2 kinetics but alters the pV̇O2 slow-component response, possibly as a result of the effects of NaHCO3 ingestion on muscle pH.
AB - Purpose: The influence of metabolic alkalosis (ALK) on pulmonary O 2 uptake (pV̇O2) kinetics during high-intensity cycle exercise is controversial. The purpose of this study was to examine the influence of ALK induced by sodium bicarbonate (NaHCO3) ingestion on pV̇O2 kinetics, using a sufficient number of repeat-step transitions to provide high confidence in the results obtained. Methods: Seven healthy males completed step tests to a work rate requiring 80% pV̇O 2max on six separate occasions: three times after ingestion of 0.3 g·kg-1 body mass NaHCO3 in 1 L of fluid, and three times after ingestion of a placebo (CON). Blood samples were taken to assess changes in acid-base balance, and pV̇O2 was measured breath-by-breath. Results: NaHCO3 ingestion significantly increased blood pH and [bicarbonate] both before and during exercise relative to the control condition (P < 0.001). The time constant of the phase II pV̇O2 response was not different between conditions (CON: 29 ± 6 vs ALK: 32 ± 7 s; P = 0.21). However, the onset of the pV̇O2 slow component was delayed by NaHCO3 ingestion (CON: 120 ± 19 vs ALK: 147 ± 34 s; P < 0.01), resulting in a significantly reduced end-exercise pV̇O2 (CON: 2.88 ± 0.19 vs ALK: 2.79 ± 0.23 L-min-1; P < 0.05). Conclusions: Metabolic alkalosis has no effect on phase II pV̇O2 kinetics but alters the pV̇O2 slow-component response, possibly as a result of the effects of NaHCO3 ingestion on muscle pH.
UR - http://www.scopus.com/inward/record.url?scp=33750706193&partnerID=8YFLogxK
U2 - 10.1249/01.mss.0000233791.85916.33
DO - 10.1249/01.mss.0000233791.85916.33
M3 - Article
C2 - 17095923
AN - SCOPUS:33750706193
SN - 0195-9131
VL - 38
SP - 1909
EP - 1917
JO - Medicine and Science in Sports and Exercise
JF - Medicine and Science in Sports and Exercise
IS - 11
ER -