Induced Metabolic Alkalosis Affects Muscle Metabolism and Repeated-Sprint Ability

BISHOP, DAVID; EDGE, JOHANN; DAVIS, CINDY; GOODMAN, CARMEL

Medicine & Science in Sports & Exercise:
BASIC SCIENCES: Original Investigations
Abstract

BISHOP, D., J. EDGE, C. DAVIS, and C. GOODMAN. Induced Metabolic Alkalosis Affects Muscle Metabolism and Repeated-Sprint Ability. Med. Sci. Sports Exerc., Vol. 36, No. 5, pp. 807–813, 2004.

Purpose: The purpose of this study was to assess the effects of induced metabolic alkalosis, via sodium bicarbonate (NaHCO3) ingestion, on muscle metabolism and power output during repeated short-duration cycle sprints.

Methods: Ten active females (mean ± SD: age = 19 ± 2 yr, V̇O2max = 41.0 ± 8.8 mL·kg −1·min −1) ingested either 0.3 g·kg −1 NaHCO3 or 0.207 g·kg −1 of NaCl (CON), in a double-blind, random, counterbalanced order, 90 min before performing a repeated-sprint ability (RSA) test (5 × 6-s all-out cycle sprints every 30 s).

Results: Compared with CON, there was a significant increase in resting blood bicarbonate concentration [HCO3] (23.6 ± 1.1 vs 30.0 ± 3.0 mmol·L −1) and pH (7.42 ± 0.02 vs 7.50 ± 0.04), but no significant difference in resting lactate concentration [La] (0.8 ± 0.2 vs 0.8 ± 0.3 mmol·L −1) during the NaHCO3 trial. Muscle biopsies revealed no significant difference in resting muscle [La], pH, or buffer capacity (βin vitro) between trials (P > 0.05). Compared with CON, the NaHCO3 trial resulted in a significant increase in total work (15.7 ± 3.0 vs 16.5 ± 3.1 kJ) and a significant improvement in work and power output in sprints 3, 4, and 5. Despite no significant difference in posttest muscle pH between conditions, the NaHCO3 trial resulted in significantly greater posttest muscle [La].

Conclusions: As NaHCO3 ingestion does not increase resting muscle pH or βin vitro, it is likely that the improved performance is a result of the greater extracellular bufferconcentration increasing H+ efflux from the muscles into the blood. The significant increase in posttest muscle [La] in NaHCO3 suggests that an increased anaerobic energy contribution is one mechanism by which NaHCO3 ingestion improved RSA.

Author Information

Team Sport Research Group, School of Human Movement and Exercise Science, The University of Western Australia, Crawley, WA, AUSTRALIA

Address for correspondence: David Bishop Ph.D., Team Sport Research Group, School of Human Movement and Exercise Science, The University of Western Australia, Crawley, WA 6009, Australia; E-mail: dbishop@cyllene.uwa.edu.au.

Submitted for publication March 2003.

Accepted for publication December 2003.

©2004The American College of Sports Medicine