크레아틴 구강 섭취: 작용기전, 근력증가 및 축적방법 = Creatine Oral Supplementation: Muscle Strength, Mechanism of Action, and Loading Protocol

다국어 초록 (Multilingual Abstract)

Creatine monohydrate(Cr), a popular, commercially sold supplement in easy is recognized as a relatively safe ergogenic aid(Ransone & Park, 2002). In general, athletes often use Cr supplement forenhancing muscle strength, muscle mass, weight, and quicker recovery. Recent data indicate that athletes may not be using acutely Cr as a sports performance booster per se but instead use Cr chronically as a training aid to increase intense resistance training workouts during off-season(Rawson & Volek, 2003). Several potential mechanisms could be responsible for increased strength power exercise performance following acute and chronical Cr supplementation; 1) the increase of ATP synthesis by Cr supplementation. 2) the increase of energy supply through anaerobic glycolysis because regeneration of ATP from PCr buffers hydrogen ions. 3) hydrogen ion buffering may also facilitate PCr resynthesis following or between exercise bouts due to low pH slowing PCr resynthesis. 4) muscle relaxation time following contraction appears to be shortened following Cr-loading via Ca2+-ATPase activity and rate of cross bridge detachment(Francaux et al., 2000; Harris et al., 1992; Lemon, 2002; Arnold et al, 1984; van Leemputte et al., 1999). Therefore, the resulting increased muscle stores of both Cr and PCr should make it possible to prolong one`s maximal effort time and/or shorten recovery time due to an enhanced ability to regenerate ATP. This may provide an additional load for increasing muscle strength and hypertrophy. However, the content of muscle Cr is depending on method, dose and time of Cr supplementation(Ziegenfuss et al., 2002; Sora et al., 1994; Preen et al., 2003). The time of Cr supplement that has each different Cr dose is divided into three phases; First, the ingestion with Cr 20g/d (4×5g, 2-3h interval)for 5-6d, called loading phase. Second, after 5-6d loading phase, ingestion with 2g /d for 4-6 weeks, called maintenance phase. Third, after maintenance phase, no ingestion with Cr for 3-4 weeks, called wash out phase. As the method of Cr supplementation, Cr supplemtation(4×5g, for 5-6d) with simple carbohydrate(CHO) ingestion(4×1g/kg in body weight) or combined protein and simple CHO ingestion(4×50g protein+50g CHO). Otherwise, if somebody has any side effect on ingestion with simple CHO, either low intensity of aerobic exercise spending 1h may increase Cr content in muscle. In the last time, the only reported side effect related Cr supplementation appears to be an increase in total body mass, probably due to an increase in intracellular water content and increase lean body mass. In general, body weight will be increase about 0.5-2kg during initial 3-5d Cr ingestion(Haussinger et al., 1993). In the future, additional research involving Cr supplementation should determine a various effect on health related issues.

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