Due to the growing concerns of the high cost, health consequences, and illegal nature of some steroids, many organizations have formed in response and have deemed themselves "natural" bodybuilding competitions. In addition to the concerns noted, many promoters of bodybuilding have sought to shed the "freakish" perception that the general public has of bodybuilding and have successfully introduced a more mainstream audience to the sport of bodybuilding by including competitors whose physiques appear much more attainable and realistic.
For a 180 lb (82 kg) person, this translates to 25 g/day during the loading phase and 2.5 g/day afterward, although many users take 5 g/day due to the low price of creatine and the possibility of experiencing increased benefits. Higher doses (up to 10 g/day) may be beneficial for people with a high amount of muscle mass and high activity levels or for those who are non-responders to the lower 5 g/day dose.
When lifting to complete fatigue, it takes an average of two to five minutes for your muscles to rest for the next set. When using lighter weight and more repetitions, it takes between 30 seconds and a minute for your muscles to rest. For beginners, working to fatigue isn't necessary, and starting out too strong can lead to too much post-exercise soreness.
When endothelial cells have a higher creatine concentration, they appear to be mildly less permeable when incubated with 0.5-5mM creatine, while the higher concentration (5mM) is able to fully ablate TNF-α-induced neutrophil adhesion and both E-selectin and ICAM-1 expression. This effect was prevented with ZM241385, an A2A (adenosine) receptor antagonist, and since adenosine released by this receptor is known to be protective of endothelial cells, it is thought that creatine works vicariously through this receptor and adenosine release, thought to be due to releasing ATP (occurs in response to stress) which protects the cell via the A2A signaling system.
In regard to the blood brain barrier (BBB), which is a tightly woven mesh of non-fenestrated microcapillary endothelial cells (MCECs) that prevents passive diffusion of many water-soluble or large compounds into the brain, creatine can be taken into the brain via the SLC6A8 transporter. In contrast, the creatine precursor (guanidinoacetate, or GAA) only appears to enter this transporter during creatine deficiency. More creatine is taken up than effluxed, and more GAA is effluxed rather than taken up, suggesting that creatine utilization in the brain from blood-borne sources is the major source of neural creatine. However, “capable of passage” differs from “unregulated passage” and creatine appears to have tightly regulated entry into the brain in vivo. After injecting rats with a large dose of creatine, creatine levels increased and plateaued at 70uM above baseline levels. These baseline levels are about 10mM, so this equates to an 0.7% increase when superloaded. These kinetics may be a reason for the relative lack of neural effects of creatine supplementation in creatine sufficient populations.