Effects of Sodium Bicarbonate on High-Intensity Endurance Performance in Cyclists: A Double-Blind, Randomized Cross-Over Trial
December
Effects of Sodium Bicarbonate on High- Intensity Endurance Performance in Cyclists: A Double-Blind, Randomized Cross-Over Trial
Florian Egger * 0 1
Tim Meyer 0 1
Ulf Such 0 1
Anne Hecksteden 0 1
0 Institute of Sports and Preventive Medicine, Saarland University , Saarbru cken , Germany
1 Editor: Conrad P. Earnest, Texas A&M University , United States of America
Background: While the ergogenic effect of sodium bicarbonate (BICA) on shortterm, sprint-type performance has been repeatedly demonstrated, little is known about its effectiveness during prolonged high-intensity exercise in well-trained athletes. Therefore, this study aims to examine the influence of BICA on performance during exhaustive, high-intensity endurance cycling. Methods: This was a single-center, double-blind, randomized, placebo-controlled cross-over study. Twenty-one well-trained cyclists (mean SD: age 248 y, BMI 21.31.7, VO2peak 67.39.8 ml?kg21?min21) were randomly allocated to sequences of following interventions: oral ingestion of 0.3 g?kg21 BICA or 4 g of sodium chloride (placebo), respectively. One h after ingestion subjects exercised for 30 min at 95% of the individual anaerobic threshold (IAT) followed by 110% IAT until exhaustion. Prior to these constant load tests stepwise incremental exercise tests were conducted under both conditions to determine IAT and VO2peak. Analysis of blood gas parameters, blood lactate (BLa) and gas exchange measurements were conducted before, during and after the tests. The main outcome measure was the time to exhaustion in the constant load test. Results: Cycling time to exhaustion was improved (p,0.05) under BICA (49.511.5 min) compared with placebo (45.09.5 min). No differences in maximal or sub-maximal measures of performance were observed during stepwise incremental tests. BICA ingestion resulted in an increased pH, bicarbonate concentration and BLa before, throughout and after both exercise testing modes. Conclusion: The results suggest that ingestion of BICA may improve prolonged, high-intensity cycling performance. Trial Registration: German Clinical Trials Register (DRKS) DRKS00006198.
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During prolonged cycling the ability to sustain a high power output is limited by
the resources of the athlete to resist fatigue. To date, the cause of fatigue is
controversial and performance may be limited by numerous factors, including
physiological and psychological components [1]. However, for high-intensity
exercise perturbations in both blood and muscle acid-base balance are associated
with a decline in work rate and performance [24]. Thus, it has been assumed that
muscle fatigue occurring in high-intensity exercise is mainly caused by the
accumulation of hydrogen ions (H+) in the myoplasm [2, 5]. The cellular
mechanisms include detrimental effects on myofilament interaction [6], glycolytic
flux [4] and sarcoplasmatic reticulum function [7]. The ability of the body to
prevent or delay these force limiting processes is determined by the capacity of its
intrinsic buffering systems [5], which counteract the accumulation of H+ both
inside and outside the cell [8].
Supplementation of alkalizing agents such as sodium bicarbonate (BICA)
indirectly affects intramuscular pH by increasing the H+ concentration gradient
across the sarcolemma [9]. As a result, the co-transport of H+ and lactate from the
myoplasm is enhanced [10]. These findings suggest that increased extracellular
buffering capacity may influence muscle function and potentially improve exercise
performance during continuous cycling.
Consequently, BICA has been studied as a potential ergogenic substance in
several trials, mainly with a focus on short-term, sprint-type exercise. In a recently
published meta-analysis it was concluded that BICA can be used as an ergogenic
aid in short-term, high-intensity exercise [11]. By contrast, only few studies
investigated the ergogenic potential of BICA in prolonged, high-intensity exercise
with controversial findings [1216]. These studies are based on small sample sizes
and, in part [14, 15], on subjects who are not habituated to the applied exercise
mode. This is despite the relevance for typical competition modes (especially in
cycling) and the lower variability of performance in trained subjects. Therefore the
aim of this study was to investigate the effects of BICA supplementation on
performance during prolonged, high-intensity cycling to exhaustion in
welltrained athletes.
Participants were recruited between May 2011 and October 2011 through email.
Twenty-one healthy, well-trained cyclists (16 male, 5 female; mean SD: age
248 y, BMI 21.31.7, VO2peak 67.39.8 ml?kg21?min21) met the following
criterion for inclusion in the study: a maximal performance during a stepwise
incremental cycle test of at least 4.5 W?kg21 for females and 5.0 W?kg21 for
males, respectively. The sample consisted of nine racing bikers, nine mountain
bikers and three triathletes. On their first visit to the laboratory ea (...truncated)