Enhancing athletic performance through high-intensity interval training and sodium bicarbonate supplementation

Introduction: Metabolic acidosis is a by-product of the energy production process required during high-intensity exercise, and it is thought to play a part in influencing muscle function and fatigue. Consequently, the efficacy of an athlete‟s intra- and extracellular buffering systems may influence their performance during an exercise task. These buffering systems can be enhanced through exercise training and nutritional supplementation. Therefore, the purpose of this series of studies was to investigate combined training and sodium bicarbonate (NaHCO3) supplementation techniques for enhancing performance in well-trained athletes. Study 1. The aim of this study was to evaluate high-intensity interval training (HIT) for improving performance in already well-trained athletes. To achieve this we compared traditional rowing training (CT) to HIT in state-representative rowers. Following baseline testing (2000 m rowing test, incremental rowing test) 10 rowers were randomly allocated to HIT or CT, which they performed seven times over a 4-week period, after posttreatment testing the rowers were allocated to the alternative training method, completing a cross-over design. The HIT produced significantly greater improvements in 2000 m time, 2000 m power and relative VO2 peak when compared to CT (P < 0.05). It was concluded that four weeks of HIT improves 2000 m time-trial performance and relative VO2 peak in competitive rowers, more than CT. Study 2. After establishing that HIT was effective in improving rowing performance the next step was to investigate if the combination of HIT and NaHCO3 supplementation could further enhance performance. However, the research literature was still equivocal as to the most effective method of NaHCO3 supplementation. Consequently, the aim of Study 2 was to compare acute NaHCO3 loading with serial NaHCO3 loading (split doses over three days) in well-trained cyclists to establish which method was best for producing performance improvements and enhanced acid-base balance with minimal side effects. Eight male cyclists completed three tests in a double blind, randomised design over a three week timeframe: acute NaHCO3 loading (AL), serial NaHCO3 loading (SL) and a placebo loading condition (P). Following each loading protocol, cyclists completed a 4-min performance test on a cycling ergometer. Both the AL and SL trials produced a significantly higher average power in the 4-min test when compared to the P trial (P < 0.05), with no significant difference between AL and SL trials (P = 0.29). The improvements in performance associated with the SL trial were despite any changes to the measure blood-gas variables (pH and HCO3-). It was concluded that SL may provide a convenient and practical alternative approach for athletes preparing for competition; however, AL was the most effective for altering acid-base balance as well as improving performance with minimal negative side-effects, and was deemed the most appropriate method to use when combing HIT and NaHCO3. Study 3. With appropriate protocols for both HIT and NaHCO3 loading in well-trained athletes confirmed, the aim of Study 3 was to combine these two strategies and investigate whether there was any additive benefit when used in a chronic training setting. Subjects were 12 elite rowers preparing for international competition. Following baseline testing, rowers were allocated to either NaHCO3 (ALK) or a placebo (PLA) group (sodium chloride matched for equimolar sodium content). Both groups performed 8 HIT sessions over a 4-week period. Prior to each HIT session, subjects were required to ingest NaHCO3 or a placebo substance. The 2000 m time-trial performance improved after 4 weeks of HIT; however, there were no statistically significant performance improvements (P > 0.05)attributable to the NaHCO3 supplementation during HIT training of fixed volume and intensity. Study 4. Due to the results from Study 2 and 3, along with some inconsistencies in the literature regarding the influence of NaHCO3 loading on athletic performance, it was hypothesised that a possible reason for lack of performance improvements after NaHCO3 supplementation was the use of sodium chloride (NaCl) as a placebo. The sodium content has been proposed to provide some performance benefits, possibly through blood volume shifts, obscuring some of the benefits associated with NaHCO3 supplementation, limiting its use as a valid placebo substance. Therefore the aim of Study 4 was to compare NaHCO3 and NaCl to a physically inert substance by evaluating the haematocrit changes and their influence on high-intensity cycling performance. Subjects undertook three tests in a random, double-blind design over a one week timeframe: NaHCO3 loading (SB), NaCl loading (SC) and dextrose loading (D). Following each loading protocol, subjects completed a 2-min performance test on a cycling ergometer. The SB trial produced a significantly higher (P 0.05). It was concluded that the HCO3- not the Na+ was primarily responsible for providing any ergogenic benefit during high-intensity exercise performance. Conclusions: The findings from these studies suggest that independently, both HIT and NaHCO3 supplementation can improve high-intensity exercise performance in well-trained athletes. However, this thesis provides the first study to investigate the combination of these two techniques in highly-trained athletes and provides evidence that such an approach does not lead to additional performance gains in this population; however, further research is warranted. The findings from the final study of the thesis suggest that it is the HCO3- content in NaHCO3 which is likely to facilitate performance benefits more so than the Na+ content. The findings of the studies included in this thesis are applicable to high-intensity exercise performance in the context of high-level athletic competition. The research adds to the knowledge base regarding practical information for athletes and coaches in terms of novel NaHCO3 loading and interval training protocols while providing likely performance outcomes