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Effects of Sodium Bicarbonate Ingestion on Prolonged Intermittent Exercise

PRICE, MIKE; MOSS, PAUL; RANCE, STUART

Medicine & Science in Sports & Exercise: August 2003 - Volume 35 - Issue 8 - pp 1303-1308
BASIC SCIENCES: Original Investigations

PRICE, M., P. MOSS, and S. RANCE. Effects of Sodium Bicarbonate Ingestion on Prolonged Intermittent Exercise. Med. Sci. Sports Exerc., Vol. 35, No. 8, pp. 1303–1308, 2003.

Purpose: The aim of this study was to determine the effects of sodium bicarbonate ingestion on prolonged intermittent exercise and performance.

Methods: Eight healthy male subjects (mean ± SD: age 25.4 ± 6.4 yr, mass 70.9 ± 5.1 kg, height 179 ± 7 cm, V̇O2max 4.21 ± 0.51 L·min−1) volunteered for the study, which had received ethical approval. Subjects undertook two 30-min intermittent cycling trials (repeated 3-min blocks; 90 s at 40% V̇O2max, 60 s at 60% V̇O2max, 14-s maximal sprint, 16-s rest) after ingestion of either sodium bicarbonate (NaHCO3; 0.3 g·kg−1) or sodium chloride (NaCl; 0.045 g·kg−1). Expired air, blood lactate (BLa), bicarbonate (HCO3), and pH were measured at rest, 30 and 60 min postingestion, and during the 40% V̇O2max component of exercise (4, 10, 16, and 29 min).

Results: After ingestion, pH increased from rest to 7.46 ± 0.03 and 7.40 ± 0.01 for NaHCO3 and NaCl, respectively (main effect for time and trial; P < 0.05). Values decreased at 15 min of exercise to 7.30 ± 0.07 and 7.21 ± 0.06, respectively, remaining at similar levels until the end of exercise. BLa peaked at 15 min (12.03 ± 4.31 and 10.00 ± 2.58 mmol·L−1, for NaHCO3 and NaCl, respectively; P > 0.05) remaining elevated until the end of exercise (P < 0.05). Peak power expressed relative to sprint 1 demonstrated a significant main effect between trials (P < 0.05). Sprint 2 increased by 11.5 ± 5% and 1.8 ± 9.5% for NaHCO3 and NaCl, respectively. During NaHCO3, sprint 8 remained similar to sprint 1 (0.2 ± 17%), whereas a decrease was observed during NaCl (−10.0 ± 16.0%).

Conclusion: The results of this study suggest that ingestion of NaHCO3 improves sprint performance during prolonged intermittent cycling.

The ingestion of sodium bicarbonate between 1 and 3 h before exercise has been shown to increase the body’s alkaline reserve (7,20) in an attempt to try and improve anaerobic performance. Studies examining such an effect on sprint performance have demonstrated both positive effects (2,22) and no effects (13,18) on performance outcomes.

More recently studies have examined the affects of bicarbonate ingestion upon more prolonged type exercise (7,20). For example, Galloway and Maughan (7) examined 1 h of cycle exercise at 70% V̇O2max after either bicarbonate or placebo (CaCO3) ingestion. The results indicated that the induced alkalosis increased lactate efflux from muscle although the effects on performance were not examined. Stephens et al. (20) examined a similar duration protocol involving two exercise intensities (30 min at 77% V̇O2max, followed by completion of a known amount of work at ∼ 80% V̇O2max, ∼ 30 min), concluding that bicarbonate ingestion did result in a relatively small muscle alkalosis but with no effect on muscle metabolism or intense endurance performance.

Although the above studies have examined exercise of longer durations, the protocols employed have not represented exercise patterns typically experienced by those involved in team sports, i.e., intermittent exercise. Prolonged intermittent exercise protocols reported in the literature typically include exercise intensities representative of walking, jogging/cruising, and sprinting (5,17,19) and produce blood lactate values that are significantly greater than for continuous exercise of a matched energy expenditure and duration (3). As existing prolonged exercise studies of bicarbonate ingestion have suggested increased lactate efflux during longer exercise durations (7,20), this may be beneficial to intermittent exercise where greater rates of anaerobic energy production occur with corresponding alterations to muscle homeostasis (3). Therefore, the aim of this study was to examine the effects of bicarbonate ingestion upon prolonged intermittent exercise and performance.

School of Science and the Environment, Coventry University, Coventry, UNITED KINGDOM

Address for correspondence: Dr. Mike Price, School of Science and the Environment, Coventry University, Priory Street, Coventry, CV1 5FW, United Kingdom; E-mail: m.price@coventry.ac.uk.

Submitted for publication November 2002.

Accepted for publication March 2003.

©2003The American College of Sports Medicine