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) . 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 [2,3,4]. 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 . Specifically, H+ impair exercise performance through inhibition of key glycolytic enzymes (i.e., phosphorylase and phosphofructokinase), impaired calcium handling, and reduced myosin ATPase activity .
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 . Sodium bicarbonate (SB) supplementation improves extracellular buffering capacity and enhances high-intensity exercise , including combat sports performance [9,10,11,12]. Lopes-Silva (2018) demonstrated that acute SB supplementation (300 mg∙kg− 1) increased glycolytic metabolism and enhanced taekwondo performance .
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 . CR supplementation increases phosphocreatine stores within the muscle by ~ 20% . The breakdown of phosphocreatine via creatine kinase supports ATP rephosphorylation during high intensity or explosive activities . The phosphocreatine energy system contributes to ~ 26–30% of the energy requirements during action phases in taekwondo . 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 . 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 . 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 . 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 . 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.