Short-term co-ingestion of creatine and sodium bicarbonate improves anaerobic performance in trained taekwondo athletes

Taekwondo is a combat sport that has been in the Olympic games since 1988 and is growing in popularity. Taekwondo involves short bursts of high-intensity activity (~ 1–5 s) interspersed with low-intensity movements (1:2–1:7 ratio) [1]. A taekwondo match is comprised of three two-minute rounds interspersed with one-minute of passive recovery. Due to the length, intensity, and intermittent nature of a taekwondo match, athletes require well-developed non-oxidative (phosphocreatine and glycolytic) and oxidative energy systems [2–4]. Throughout a match, the relative contribution from the anaerobic glycolytic system increases due to the short recovery between rounds [3, 4]. In particular, hydrogen ions (H⁺) may accumulate during a match and potentially impair performance [5]. Specifically, H⁺ impair exercise performance through inhibition of key glycolytic enzymes (i.e., phosphorylase and phosphofructokinase), impaired calcium handling, and reduced myosin ATPase activity [6].

Dietary strategies including supplements known to alter either extracellular or intracellular buffering capacity or alter the contribution from the glycolytic energy system may enhance taekwondo performance [7]. Sodium bicarbonate (SB) supplementation improves extracellular buffering capacity and enhances high-intensity exercise [8], including combat sports performance [9–12]. Lopes-Silva (2018) demonstrated that acute SB supplementation (300 mg∙kg^{− 1}) increased glycolytic metabolism and enhanced taekwondo performance [3].

Another potential dietary strategy is creatine (CR) supplementation. CR is an organic compound naturally produced in the body from reactions involving arginine, glycine, and methionine in the kidneys and liver [13]. CR supplementation increases phosphocreatine stores within the muscle by ~ 20% [13]. The breakdown of phosphocreatine via creatine kinase supports ATP rephosphorylation during high intensity or explosive activities [6]. The phosphocreatine energy system contributes to ~ 26–30% of the energy requirements during action phases in taekwondo [14]. Mechanistically, CR can act through several mechanisms including ATP rephosphorylation, and an intracellular buffer [6, 15].

In theory, co-ingestion of SB and CR may provide additional ergogenic effects since they act through different mechanisms. In a crossover design, Barber et al. (2013) supplemented trained males (n= 13) with CR (20 g) and SB (0.5 g/kg) for only 2 days (with a relatively short 3-week washout) compared to either CR or PLA alone. Mean and peak power was higher during repeated sprints following co-ingestion compared to CR or placebo (PLA) alone [16]. Six days of CR Co-ingestion (20 g∙day^{− 1}) and an acute dose of SB improved swimming performance by 1.5% in the second repeat of a 2 × 100-m freestyle swimming test compared to PLA [17]. In contrast, Griffen et al. (2015) reported no additional effect of CR and SB when compared to CR and SB alone on indices of mechanical power in well-trained males (n = 9) performing repeated Wingate tests using a cross over design with a 7-day washout between conditions [18]. A recent meta-analysis reported that chronic (500 mg∙kg^{− 1} for 5 d) but not an acute bolus of SB improved peak and mean power during anaerobic performance [19]. To date, studies have provided mixed results that may be associated with methodological limitations, such as short washout periods (≤ 3 wks), acute SB dosing, and lack of comparison groups. Therefore, the purpose of this study was to examine the effects of CR monohydrate and SB co-ingestion on mean power (MP), peak power (PP), fatigue index (FI), rating of perceived exertion (RPE), and blood lactate (BL) during a sport-specific anaerobic intermittent kick test (TAIKT) in trained taekwondo athletes compared to CR, SB, PLA, and control (CON). We hypothesized that SB and CR co-ingestion would increase MP and PP compared to CR, SB, PLA and CON. It was also hypothesized that CR and SB ingestion alone would enhance anaerobic performance compared to PLA and CON.

Participants' characteristics are shown in Table 1. There were no differences between groups for any variable at baseline (P > 0.05). There was a significant group x time interaction for body mass (P < 0.001, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\upeta}_{\mathrm{P}}^2 $$\end{document}ηP2 = 0.735). Post hoc analyses revealed that only the CR conditions increased body mass over time (CR + SB: Pre = 73.6 ± 8.4 kg, Post = 74.6 ± 8.3 kg; CR: Pre = 72.0 ± 11.0 kg, Post = 72.9 ± 11.2 kg, P < 0.001), with no other changes (SB: Pre = 71.5 ± 10.9 kg, Post = 71.5 ± 10.9 kg; PLA: Pre = 72.2 ± 7.2 kg, Post = 72.3 ± 7.2 kg, CON: Pre = 74.6 ± 6.4 kg, Post = 74.5 ± 6.5 kg, P > 0.05). FI did not change between groups over time over time between groups (P > 0.05). There was no reported gastrointestinal discomfort and the Hooper score was unaltered (P > 0.05).

The main findings of the present study were that PP and MP increased following 5 days of supplementation with CR and SB, alone and in combination. In partial support of our hypothesis, there was a greater change in MP over time following co-ingestion of CR and SB compared to only CR and SB. However, co-ingestion of CR and SB did not enhance PP compared to CR and SB alone. Following SB supplementation (CR + SB and SB alone) post-exercise BL concentrations were attenuated compared to CR, PLA, and CON.

Mechanistically, acute and chronic ingestion of SB elevates blood HCO3- and enhances extracellular buffering capacity [19]. Theoretically, SB leads to a higher efflux of free hydrogen ions (H⁺) and lactate from skeletal muscle during intense physical exercise, thus postponing fatigue and enhancing high-intensity exercise performance [19, 32]. In the present study, SB enhanced exercise performance; however, contrary to previous studies reporting higher post exercise BL following SB in combat athletes [3, 9, 11] we found a lower post-exercise lactate concentration compared to that in PLA, CON, and CR groups. Given that BL concentrations represent the aggregate of anaerobic glycolytic production and lactate clearance. These findings may have been due to inter-individual heterogeneity in aerobic capacity possibly influencing lactate removal [33]. Therefore, future research with direct measures is warranted.

In line with previous literature, SB improved MP and PP compared to PLA and CON. For instance, Tobias et al. [11] and Oliveira et al. [34] found that 5–7 days of SB (500 mg∙kg-1) enhanced repeated Wingate performance by 7 and 2.9%, respectively. Ergogenic effects of chronic SB supplementation also were observed during repeated Anaerobic Sprint Test in elite soccer players [35]. Furthermore, a recent meta-analysis reported that chronic (500 mg∙kg^-1 for 5 d) but not an acute bolus of SB improved PP and MP during anaerobic performance [19]. In support of our finding, a meta-analysis by Lopes-Silva and colleagues [19] reported higher PP after chronic SB supplementation. Although, the main energy system to generate higher PP largely depends on the PCr pathway, it has been well documented that the glycolytic pathway has already been activated to synthesize ATP within this time frame [6, 19]. Our findings provide further support that 5 days’ supplementation protocol was effective with no reported adverse effects which makes this strategy applicable in real sporting events.

With respect to combat sports, SB supplementation has been advantageous to enhance sport performance, including a karate-specific aerobic test (KSAT) [9], as well as a simulated matches of taekwondo [3], boxing [12], and a Judo [10], which supports our findings in taekwondo athletes during TAIKT .

The CR supplementation, which is known to enhance muscle CR and phosphocreatine (PCr) stores [25], improves anaerobic performance through several potential mechanisms [8]. Elevated PCr stores enhance the capacity to rephosphorylate ATP [36] and delay contributions from the glycolytic energy system. Importantly, PCr hydrolysis consumes a H⁺ ion and acts as a buffer against acidosis during exercise [6, 15]. CR also aids in the shuttling of high-energy phosphate metabolites between sites of ATP production (i.e. mitochondria) and the cytosol, leading to increased oxidative recovery [13]. In addition, CR increases calcium re-uptake into the sarcoplasmic reticulum augmenting myofibrillar cross-bridge cycling and force development [37]. It is estimated that the ATP-PCr energy system contributes 26–30% of total energy production during an attack and counter-attack action in taekwondo [1, 14], and therefore CR supplementation may enhance taekwondo performance. We provide evidence that CR supplementation for 5 days (sufficient to saturate the muscle) enhances MP and PP compared to PLA and CON. In agreement with our findings, short-term and long-term CR supplementation have been shown to improve six 35-m maximal sprints using a running anaerobic sprint test in male and female soccer players [38, 39].

Concerning combat sports, CR supplementation has shown equivocal findings. For example, CR failed to enhance anaerobic power in trained wrestlers [40] and taekwondo athletes [41], while CR supplementation in elite wrestlers improved Wingate performance [42]. Five days of CR (20 g∙day^{− 1}) increased MP during a 30-s Wingate in elite wrestlers [42]. Differences between studies may be associated with methodological differences including training status, fiber type differences, baseline CR levels, and conducted anaerobic test. The present study was the first to examine CR on taekwondo athletes using sport-specific test and found positive results.

Although, CR and SB co-ingestion did not result in a higher PP compared to when CR and SB consumed separately, but it was higher than PLA and CON. These findings partially support previous research examining CR and SB co-ingestion [16, 17]. Barber et al. reported a 7% improvement following 2 days of CR and SB on relative peak power during repeated Wingate compared to CR (4%) and PLA [16]; however, this study did not include a SB alone condition for further comparison. In another study, CR co-ingestion over 6 days (20 g∙day^{− 1}) and an acute dose of SB resulted in a 1.5% improvement in swimming performance in the second repeat of a 2 × 100-m freestyle swimming test compared to PLA [17]. On the other hand, Griffen et al. reported no additional ergogenic effect of 7 days of CR (20 g/day) and an acute 300 mg∙kg^{− 1} dose of SB supplementation compared to CR and SB alone on indices of mechanical power output during repeated Wingate test [18]. The mixed results could be attributed to some methodological differences existing between studies. For example, Barber et al. [16] and Mero et al. [17] did not include a SB alone condition thus making it difficult to interpret whether CR + SB was superior to either supplement alone. Another discrepancy of previous research was employing the acute SB supplementation strategy and/or the short (i.e., 2 days) CR loading period [19]. In the present study, a chronic SB (500 mg∙kg^{− 1} for 5 days) supplementation strategy was used with 5 days of CR loading which is known to saturate the muscle [25]. Although the co-ingestion did not further augment PP compared to either supplement alone, but MP was augmented to a greater degree following CR + SB compared to SB and CR alone. The precise mechanism(s) explaining the summative effect of CR + SB co-ingestion in the present study remains to be elucidated.

There are several limitations to the present study. First, we were unable to measure blood HCO3- and pH as well as intramuscular CR measures which would have provided a better mechanistic insight to explain observed differences in co-ingestion versus the single-ingredient conditions. Second, our participants were national or premier league caliber athletes. Due to training commitments, conducting a crossover study design (which would have enhanced the statistical power) was challenging to achieve. Third, we only assessed anaerobic performance by using a sport-specific test while future studies investigating other fitness components such as aerobic, muscular strength and power, flexibility, speed, and agility that are critical for taekwondo success are required [1, 28]. Lastly, we only included males with low participant sample size in each group. Future research in females with a larger sample size is required due to potential sex-based differences in response to creatine and sodium bicarbonate [8].

Creatine and sodium bicarbonate supplementation have both been shown to enhance anaerobic performance in combat sports athletes. There is limited research using a sufficient CR loading phase with chronic SB supplementation on anaerobic performance. The current study found improvements in PP and MP compared to a PLA or CON when CR and SB were ingested alone using a taekwondo specific test. Co-ingestion of CR with SB further augmented MP compared to CR and SB alone. As such, coaches and athletes could consider utilizing these supplements to provide a possible performance advantage; however, individual responsiveness may need to be considered. Thus, short-term CR (20 g∙day^{− 1}) and SB (500 mg∙kg^{− 1}∙day^{− 1}) alone enhance TAIKT performance compared to PLA and CON in trained taekwondo athletes. CR co-ingested with SB augments MP during an anaerobic sport-specific test compared to CR and SB alone.