The first published results (not blinded) noted that a loading phase of 20g of creatine for a week, followed by 3g daily for up to six months, was able to enhance maximal voluntary isometric muscular contraction (MVIC) on a dynamometer for both the knee and elbow joints, with enhanced fatigue resistance on the same joints in more than half of subjects (53-70% response rate).
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.
These effects were noted before in a preliminary study of depressed adolescents (with no placebo group) showing a 55% reduction in depressive symptoms at 4g daily when brain phosphocreatine levels increased. Other prelimnary human studies suggest creatine might lessen unipolar depression and one study on Post-Traumatic Stress Disorder (PTSD) noted improved mood as assessed by the Hamilton Depression Rating Scale.
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Bodybuilders also understand how to diet. This is perhaps the most important aspect other athletes can learn from. I can’t think of any athlete that comes close to bodybuilders who know how to build massive amounts of muscle and then can diet with the type of precision that gets them absolutely shredded on a specific date. Most resistance training sports use weight classes to compete. It doesn’t take a rocket scientist to see that shedding body fat without losing muscle can be a major advantage. Competing at a lower weight class because you are leaner while maintaining strength and performance is a very valuable and effective strategy. Diet to build LEAN muscle to keep weight low for a competitive advantage.
In the stomach, creatine can degrade by about 13% due to the digestive hormone pepsin, as assessed by simulated digestion. Although creatinine is a known byproduct of creatine degradation, simulated gastric digestion did not increase creatinine levels, indicating that other breakdown products were formed. However, creatinine was noted to increase in the presence of pancreatin, a mixture of pancreatic enzymes.
An isolation exercise is one where the movement is restricted to one joint only. For example, the leg extension is an isolation exercise for the quadriceps. Specialized types of equipment are used to ensure that other muscle groups are only minimally involved—they just help the individual maintain a stable posture—and movement occurs only around the knee joint. Most isolation exercises involve machines rather than dumbbells and barbells (free weights), though free weights can be used when combined with special positions and joint bracing.
Polyethylene glycol is a non-toxic, water-soluble polymer that is capable of enhancing the absorption of creatine and various other substances . Polyethylene glycol can be bound with CM to form polyethylene glycosylated creatine. One study  found that 5 g/d for 28 days of polyethylene glycosylated creatine was capable of increasing 1RM bench press in 22 untrained young men but not for lower body strength or muscular power. Body weight also did not significantly change in the creatine group which may be of particular interest to athletes in weight categories that require upper body strength. Herda et al  analyzed the effects of 5 g of CM and two smaller doses of polyethylene glycosylated creatine (containing 1.25 g and 2.5 g of creatine) administered over 30 days on muscular strength, endurance, and power output in fifty-eight healthy men. CM produced a significantly greater improvement in mean power and body weight meanwhile both CM and polyethylene glycosylated form showed a significantly (p < 0.05) greater improvement for strength when compared with control group. These strength increases were similar even though the dose of creatine in the polyethylene glycosylated creatine groups was up to 75% less than that of CM. These results seem to indicate that the addition of polyethylene glycol could increase the absorption efficiency of creatine but further research is needed before a definitive recommendation can be reached.
These supplements can vary considerably from product to product in ingredients, serving sizes, and more. But the goal of each of them is generally quite similar. Most bodybuilding supplements are designed to help stimulate new muscle growth, cut away excess fat, and improve the recovery process so that you can get the most out of each trip to the gym.