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Effect of sodium bicarbonate ingestion during 6 weeks of HIIT on anaerobic performance of college students

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  • Effect of sodium bicarbonate ingestion during 6 weeks of HIIT on anaerobic performance of college students

    High-intensity interval training (HIIT) refers to a training protocol involving multiple bouts of high-intensity exercise or all-out sprints that are interspersed with recovery periods [1]. Results of previous studies support the idea that HIIT significantly promotes both aerobic and anaerobic exercise capacity [25]. Studies have found that aerobic capacity could be positively influenced by HIIT through an increase in oxidative enzymes [6], higher oxidative enzymes activity [79], better oxygen transfer to cells [10], more mitochondria per cell, and better mitochondrial function [1012]. Tabata et al. (1996) compared the effects of endurance training and HIIT training on anaerobic abilities [2]. In this study, eight sets of 20 s high-intensity exercise, with 10 s intervals between each set, for 5 days/week were completed each training day by the HIIT group [2]. After 6-weeks of training, the anaerobic capacity of the HIIT group increased by 28%, while the endurance training experienced no significant change [2]. Although other studies assessing HIIT have used different training methods, training protocols (training equipment, training intensity and time, etc.), and subject groups, most results suggest that HIIT training effectively improves anaerobic capacity [1316]. Studies have shown that, because of the high intensity and short duration, HIIT is characterized by an energy supply derived primarily from anaerobic metabolism, although it is known that all three energy systems support the exercise in different proportions during different exercise time periods [1719]. The ability of maintaining the required power output is related to the capacity to continuously supply ATP by anaerobic glycolysis. The benefit of pursuing higher power output in high-intensity exercise alters the kinetics of oxygen uptake (VO2), which can also support anaerobic performance by diminishing the demand on relatively limited anaerobic fuel sources. The study of Tomlin et al. (2001) showed a positive relationship between aerobic fitness and power recovery from high intensity intermittent exercise [20]. It appears, therefore, that the improvement in anaerobic capacity during HIIT training is likely from the combined results of enhanced phosphocreatine energy supply capacity [21], improved glycolytic enzyme activity [22, 23], and enhanced aerobic metabolism [20].
    While in a state of rest, human blood is slightly alkaline (pH ~ 7.4), while muscle is neutral (pH ~ 7.0). Constant mediation of the blood and muscle acid-base balance is one of the important requirements to assure normal cellular metabolism. By neutralizing excess acidity and/or alkalinity, buffering systems in the body attempt to maintain the pH in a desired/healthy range. A primary buffering system is the carbonic acid (H
    3)-bicarbonate ion (HCO
    3) system, which functions through the reaction below:
    $$ {\mathrm{H}}^{+}+{{\mathrm{H}\mathrm{CO}}_3}^{-}\leftrightharpoons {\mathrm{H}}_2{\mathrm{CO}}_3\leftrightharpoons {\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2 $$

    Studies have confirmed that acidosis negatively impacts the release of calcium ions during muscle contraction, the activation of electrical signal receptors, the binding of calcium ions to troponin C, and metabolic enzyme activity [2427]. These changes have the effect of hindering ATP re-synthesis and slowing glycolysis. Acidosis can result from a drop in intracellular pH during short-duration intense anaerobic exercise. Studies have found that HCO3 can buffer the accelerated release of hydrogen ions associated with this intense anaerobic activity, thereby lowering acidosis. In addition, the sodium ion (Na+) in sodium bicarbonate (HCO3) can be beneficial by neutralizing the acid impact of the hydrogen ion (H+). It has also been established that ingestion of Na+ can increase the plasma volume [28], which could be an additional benefit to anaerobic activity by creating an enlarged buffering potential through dilution of the H+ concentration. Other studies also have found that acute or chronic exogenous HCO3 may improve performance in 400 and 800 m races, 2 min sprints, the Wingate test, and other anaerobic activities [2935].
    The timing of acute HCO3 supplementation in past studies typically ranges from 1 to 3 h prior to exercise, which significantly raises the blood HCO3 level and pH in the blood [36]. Studies have found that the activity of H+ transmembrane protein increases in proportion to the rise of intracellular H+ concentration [37]. As a result, the H+ and lactate ions, which overflow from the cells due to exercise, can be buffered by HCO3. Thus, the acid-buffering capacity of the muscles is improved while the increase of H+ in muscles is reduced to delay muscular fatigue.
    A meta-analysis summarizing 29 studies found that supplementation of HCO3 can improve anaerobic exercise capacity, significantly extending the time of exercise to exhaustion [38]. Studies also suggest that the greater the pH drop during exercise, the more beneficial the supplementation of HCO3 [34, 39]. Some studies have compared the effects of acute and chronic HCO3 supplementation on anaerobic ability, with results suggesting that chronic supplementation is more effective at increasing anaerobic exercise capacity than acute supplementation. A potential problem with HCO3 supplementation is that an inappropriate dosage may result in acute gastrointestinal reactions, with symptoms that include nausea, stomach pain, diarrhea, and vomiting, all of which may negatively impact exercise performance [40]. Dose-response studies assessing commonly used HCO3 doses, typically ranging from 0.1–0.5 g/kg body mass (BM), found that the most commonly used dose was 0.3 g/kg BM [38, 4043]. Studies have also shown that chronic supplementation at doses lower than 0.3 g/kg BM results in better gastrointestinal tolerance than one-time acute and larger HCO3 supplementation dose before exercise [4446].
    Current studies have assessed the effects of HCO3 supplementation on HIIT exercise performance, but few studies have assessed the independent effects of HIIT and HCO3 on anaerobic performance. There are several studies that have also assessed the impact of HIIT with HCO3 supplementation on aerobic performance [4749]. The studies of Jourkesh et al. (2011) [47] and Edge et al. (2004) [49] found that HCO3 supplementation with HIIT positively affects aerobic capacity. In contrast, a study by Driller et al. (2013) found that this combination had the opposite effect, although the researchers hypothesized that the finding may have been due to the unique subject characteristics (highly trained members on national teams), whose aerobic performance was sufficiently well-developed that it would not likely be impacted through the addition of supplemental HCO3 [48, 50, 51]. Because of this finding, we chose healthy college students as our subjects instead of highly trained athletes, to enable a better understanding of the possible impact of HCO3 ingestion when coupled with HIIT.
    The results of past studies led us to develop a research project that would assess the combination of chronic HCO3 supplementation with HIIT training, to explore whether this intervention can effectively improve anaerobic capacity in healthy young men. We hypothesized that the combination of chronic HCO3 supplementation during HIIT will result in an improvement of anaerobic exercise performance in this population.
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