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Are you cycling your creatine? Find out why you may want to
by Bryan Haycock MS
As we approach the new millennium we find the science of building muscle progressing faster than ever before. Long gone are the days of simple trial and error when it comes to building muscle. The modern bodybuilder demands more than just "hear say" if they are to adopt a new training routine or nutritional supplement. This column was created to keep todayís bodybuilder on the cutting edge of scientific research that might benefit them in their quest for body perfection.
Are you cycling your creatine? Find out why you may want to.
Creatine supplementation in health and disease. Effects of chronic creatine ingestion in vivo: down-regulation of the expression of creatine transporter isoforms in skeletal muscle.
Guerrero-Ontiveros ML, Wallimann T.
Institute for Cell Biology, Swiss Federal Institute of Technology, ETH-Honggerberg, Zurich.
Mol Cell Biochem 1998 Jul;184(1-2):427-37
These researchers studied the in vivo effect of dietary creatine as well as 3-GPA (a creatine analog that is a competitive inhibitor of creatine entry) on the expression of the creatine transporter (creatine T). Long term feeding of rats with 3-GPA has been previously shown to decrease creatine levels in skeletal muscles without effecting creatine T expression. In this study, the expression of the creatine T was examined in rats chronically fed either 4% creatine or 2.5% GPA. Dietary creatine administered for 3-6 months, significantly lowered the expression of creatine T polypeptides. The rats fed the creatine analog GPA showed virtually no change (perhaps even a slight increase) in creatine T polypeptide expression.
The wide spread use of creatine among athletes and bodybuilders has raised concerns about possible negative side effects. Of course most of the nay sayers are looking to control its availability with little real concern for the well being of those who use it. This study has answered a question that has rested on the minds of many, which is, "Is there any reason to cycle creatine?" From the study above we see that the abundance and activity of the creatine transporter is negatively effected by long term creatine ingestion. The creatine transporter is down regulated with continued exposure to extracellular creatine.
Human skeletal muscle has an upper limit of creatine that can, or will, be contained within the cell. This limit is around 150-160 mmol/kg of dry muscle. As the intracellular concentration of creatine approaches this level, the synthesis of creatine transporters declines and even stops depending on the amount of creatine ingested over time. In the study above, it was shown that the creatine transporter is regulated by the content of creatine in the cell rather than by the interaction of creatine, or itís analog 3-GPA, with the transporter.
All the arguments about creatine absorption being a limiting factor in creatine content within the cell are bogus. Creatine does not need to be "micronized" or "effervesent" to lead to an increase in creatine content within your muscles. The activity of the creatine transporter is the limiting factor. Any trick increase in creatine absorption will only hasten creatine transporter down regulation. It only requires about 5 grams per day for 30 days to increase the content of creatine within muscle tissue to the same extent as 30 grams per day for 6 days. The sooner you reach the upper limit the sooner your muscles become unable to take up creatine. It is better to maintain sufficient levels of creatine transporters in order not to cause a rapid decline in creatine content once creatine supplementation is discontinued. Clearly there appears to be good reason to cycle creatine supplementation.
The authors of this study recommend not using creatine for over 3 months at a time. To truly cycle creatine you will have to take at least 4 weeks off. Creatine levels take at least one month to return to pre-supplement levels. It may be important to take the entire month off because one speculated mechanism of creatine transporter downregulation is that when the intracellular levels (levels inside the muscle cell) are increased the creatine transporters are taken down and not replaced as long as creatine levels remain elevated. Thus it might take as long as a month for creatine transporters to return to normal after chronic creatine supplementation. Keep in mind that no one has actually shown that long-term supplementation with creatine is a bad thing.
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It seems that creatine supplementation doesn't have much impact on creatine transporter in humans, so cycling it might be unnecessary...
Mol Cell Biochem 2003 Feb;244(1-2):159-66 Related Articles, Links
Acute and moderate-term creatine monohydrate supplementation does not affect creatine transporter mRNA or protein content in either young or elderly humans.
Tarnopolsky M, Parise G, Fu MH, Brose A, Parshad A, Speer O, Wallimann T.
Department of Medicine (Neurology and Rehabilitation), McMaster University, Hamilton, ON, Canada. email@example.com
Animal studies have shown that supra-physiological creatine monohydrate (Cr-mH) supplementation for 3 months reduced skeletal muscle creatine transporter (CRT) content. The doses of Cr-mH (1-2 g/kg/day) used in these studies were between 5 and 10 times those usually used in human studies, and it is unclear whether a down-regulation of CRT would occur in humans at the recommended doses of 0.1-0.2 g/kg/day. We measured CRT, and citrate synthase (CS) protein content using Western blotting before and after 2 months of Cr-mH supplementation and weight training in young men (N = 11 Cr-mH (0.125 g/kg/ day); N = 8 placebo). CRT and CS were also measured before and after 4 months of Cr-mH supplementation and weight training in elderly (> 65 years) men and women (N = 14 Cr-mH (0.075 g/kg/day); N = 14 placebo). Finally, CRT mRNA was measured using competitive RT-PCR before and after 8-9 days of Cr-mH loading in young men and women (N = 14, CR-mH (mean = 0.18 g/kg/day); N = 13, PL). Total creatine content was significantly elevated after the Cr-mH supplementation period as compared to placebo in each of the studies. Neither Cr-mH supplementation, nor exercise training resulted in measurable alterations in CRT protein content and acute Cr-mH loading did not alter CRT mRNA. There were no gender differences in CRT mRNA or total creatine content in the young subjects and no gender differences in total creatine content or CRT protein content in the elderly subjects. Weight training in young men did not increase CS protein content, however, in the elderly there was a significant increase in CS protein content after exercise training (p < 0.05). These results demonstrated that Cr-mH supplementation during weight training resulted in increases in skeletal muscle total creatine without reductions in CRT protein and acute Cr-mH loading did not decrease CRT mRNA content.
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hhadjo you are the bomb
fuck i wouldnt know if you were making this shit up as you went along, its so far over my head. Some of you guys post things that make my and i'm sure mosts heads spin. were the hell do you come across these articles man?
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