Activation of NMDA receptors is known to stimulate Na+,K+-ATPase activity secondary to calcineurin, which which has been confirmed with creatine in hippocampal cells (0.1-1mM trended, but 10mM was significant). This is blocked by NMDA antagonists. This increase in Na+,K+-ATPase activity is also attenauted with activation of either PKC or PKA, which are antagonistic with calcineurin.
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The majority of creatine in the human body is in two forms, either the phosphorylated form making up 60% of the stores or in the free form which makes up 40% of the stores. The average 70 kg young male has a creatine pool of around 120-140 g which varies between individuals [10,11] depending on the skeletal muscle fiber type  and quantity of muscle mass . The endogenous production and dietary intake matches the rate of creatinine production from the degradation of phosphocreatine and creatine at 2.6% and 1.1%/d respectively. In general, oral creatine supplementation leads to an increase of creatine levels within the body. Creatine can be cleared from the blood by saturation into various organs and cells or by renal filtration .
Bodybuilding is the use of progressive resistance exercise to control and develop one's musculature for aesthetic purposes. An individual who engages in this activity is referred to as a bodybuilder. In professional bodybuilding, bodybuilders appear in lineups and perform specified poses (and later individual posing routines) for a panel of judges who rank the competitors based on criteria such as symmetry, muscularity, and conditioning. Bodybuilders prepare for competitions through the elimination of nonessential body fat, enhanced at the last stage by a combination of intentional dehydration and carbohydrate loading, to achieve maximum muscular definition and vascularity, as well as tanning to accentuate the contrast of the skin under the spotlights. Bodybuilders may use anabolic steroids and other performance enhancing drugs to build muscles.
In contrast to strongman or powerlifting competitions, where physical strength is paramount, or to Olympic weightlifting, where the main point is equally split between strength and technique, bodybuilding competitions typically emphasize condition, size, and symmetry. Different organizations emphasize particular aspects of competition, and sometimes have different categories in which to compete.
Rheumatoid arthritis. Early research shows that taking creatine by mouth daily increases lean muscle mass and may improve muscle strength, but does not improve physical functioning in adults with rheumatoid arthritis. In children, taking a specific supplement containing creatine and fatty acids twice daily for 30 days might reduce pain and swelling. But the effects of creatine alone are not clear.
During the 1950s, the most successful and most famous competing bodybuilders[according to whom?] were Bill Pearl, Reg Park, Leroy Colbert, and Clarence Ross. Certain bodybuilders rose to fame thanks to the relatively new medium of television, as well as cinema. The most notable[according to whom?] were Jack LaLanne, Steve Reeves, Reg Park, and Mickey Hargitay. While there were well-known gyms throughout the country during the 1950s (such as Vince's Gym in North Hollywood, California and Vic Tanny's chain gyms), there were still segments of the United States that had no "hardcore" bodybuilding gyms until the advent of Gold's Gym in the mid-1960s. Finally, the famed Muscle Beach in Santa Monica continued its popularity as the place to be for witnessing acrobatic acts, feats of strength, and the like. The movement grew more in the 1960s with increased TV and movie exposure, as bodybuilders were typecast in popular shows and movies.
When it comes to building lean muscle, size bodybuilders are king. That’s their ultimate goal. Sure, Crossfit, powerlifting and all the other modalities will build muscle, but that’s not their focus. They want performance and any muscle they build is a side effect. Not so with bodybuilding where muscle size and shape are the priorities. Learning how to build muscle for the sake of building muscle has some benefits to the performance athlete. It allows for ais less injury prone. Its also a fact that bigger muscle contract harder regardless of technique or form, so it’s a good strategy to throw in some bodybuilder muscle building sessions here and there to give yourself stronger muscles to then train for performance. Build the muscle bigger, then train it to perform better.
In humans, studies that investigate links between serotonin and creatine supplementation find that 21 trained males, given creatine via 22.8g creatine monohydrate (20g creatine equivalent) with 35g glucose, relative to a placebo of 160g glucose, was found to reduce the perception of fatigue in hot endurance training, possibly secondary to serotonergic modulation, specifically attentuating the increase of serotonin seen with exercise (normally seen to hinder exercise capacity in the heat) while possibly increasing dopaminergic activity (conversely seen to benefit activity in the heat).
Creatine supplementation (11.4g) with glycerol (1g/kg; per se effective) and glucose (75g) in endurance runners in the heat appears to attenuate the increase in internal temperature associated with an increase in total body water of 0.71+/-0.42L, while performance (VO2 max and running economy) were unaffected over 30 minutes. Creatine is effective without glycerol (20g daily with 140g of glucose polymer over a week), again without an improvement in physical performance.
I was building up, bulking, going after the mass, which to me meant 230 pounds of sheer body weight. At that time, I didn’t care about my waist or anything else that would give me a symmetrical look. I just wanted to build a gigantic 250-pound body by handling a lot of weight and blasting my muscles. My mind was into looking huge, into being awesome and powerful. I saw it working. My muscles began bursting out all over. And I knew I was on my way.”
Bodybuilders have THE BEST mind to muscle connection of any resistance-training athletes. Ask a seasoned bodybuilder to flex their lats or their rhomboids or their hamstrings and they will do it with ease. Ask other strength athletes and you will see them struggle and although they may tense up the target muscle they will also tense up about 15 other surrounding muscles. This is because strength athletes train MOVEMENTS. They don’t care about targeting their lats. They just want to do the most pull ups. They don’t worry about feeling their quads. They just want to squat maximum weight. Although this is an expected and positive thing for the most part, there are real benefits to being able to isolate and target muscles.
One case study exists of a man with focal segmental glomerulosclerosis who experienced an accelerated rate of GFR decline during supplementation (5g thrice daily for loading, then a 2g maintenance for seven weeks) which was partially reversed upon supplement cessation. This was deemed strong circumstantial evidence, and the brand of supplement was not named. Elsewhere, interstitial nephritis associated with creatine supplementation has been reported in a man, although symptoms arose four weeks after supplementation started with no evidence to support correlation. Some studies involving athletes and various dietary supplements have attempted to draw a correlation with creatine and cases of rhabdomyolysis. Finally, one study in a diabetic person ingesting both metformin and creatine resulting in metabolic acidosis has attempted to place causation on creatine, but it did not establish causation or circumstantial evidence.