According to BodyBuilding.com, adenosine triphosphate (ATP) is made up of a nucleotide bonded to three phosphate groups. When one of those phosphate groups is cleaved from the ATP molecule, a lot of energy is made available. That energy is used to fuel chemical reactions in cells, and ATP becomes adenosine diphosphate (ADP). Creatine enables the release of energy from stored ATP and is converted to creatinine.
In vitro, creatine (0.125mM or higher) can reduce excitotoxicity from glutamate, which is thought to be secondary to preserving intracellular creatine phosphate levels. Glutamate-induced excitotoxicity is caused by excessive intracellular calcium levels resulting from ATP depletion. Since high levels of calcium inside the cell are toxic, ATP preserves membrane integrity, in part by promoting calcium homeostasis. When ATP is depleted, the sodium-potassium ATPase pump (Na+,K+-ATPase) stops working, leading to sodium accumulation in the cell. This reduces the activity of the sodium-calcium exchange pump, which, alongside a lack of ATP, reduces calcium efflux through the Na+,K+-ATPase. Thus, ATP depletion leads to intracellular calcium overload, loss of membrane potential, and excitotoxic cell death. Therefore, by helping preserve ATP levels, creatine is protective against excitotoxicity. This protective effect was noted after either creatine preloading or addition up to 2 hours after excitotoxicity. Protection from glutamate-induced toxicity also extends to glial cells and is additive with COX2 inhibition.
A child’s ability to regenerate high energy phosphates during high intensity exercise is less than that of an adult. Due to this, creatine supplementation may benefit the rate and use of creatine phosphate and ATP rephosporylation. However, performance in short duration high-intensity exercise can be improved through training therefore supplementation may not be necessary .
High extracellular creatine concentrations induce the expression of a factor that inhibits the creatine transporter (CrT). To date, neither the identity of nor mechanism for this putative CrT-suppressing factor has come to light. Future studies that are able to identify this creatine transport-suppressing factor and how it works may provide valuable insight into possible supplementation strategies that might be used to increase creatine uptake into muscle cells.
The exercises that allow you to use the greatest amount of weight are the ones that help you build muscle the fastest. These also happen to be the lifts that allow for the greatest percentage of increases in loading. We’re talking compound (multi-joint) exercises here, done with free weights. You’re not going to grow at nearly the same rate with a workout comprising machine exercises and isolation movements.
Isometric exercise provides a maximum amount of resistance based on the force output of the muscle, or muscles pitted against one another. This maximum force maximally strengthens the muscles over all of the joint angles at which the isometric exercise occurs. By comparison, weight training also strengthens the muscle throughout the range of motion the joint is trained in, but only maximally at one angle, causing a lesser increase in physical strength at other angles from the initial through terminating joint angle as compared with isometric exercise. In addition, the risk of injury from weights used in weight training is greater than with isometric exercise (no weights), and the risk of asymmetric training is also greater than with isometric exercise of identical opposing muscles.
A previous meta-analysis  reported an overall creatine supplementation effect size (ES) of 0.24 ± 0.02 for activities lasting ≤30 s. (primarily using the ATP- phosphocreatine energy system). For this short high-intensity exercise, creatine supplementation resulted in a 7.5 ± 0.7% increase from base line which was greater than the 4.3 ± 0.6% improvement observed for placebo groups. When looking at the individual selected measures for anaerobic performance the greatest effect of creatine supplementation was observed on the number of repetitions which showed an ES of 0.64 ± 0.18. Furthermore, an increase from base line of 45.4 ± 7.2% compared to 22.9 ± 7.3% for the placebo group was observed. The second greatest ES was on the weight lifted at 0.51 ± 0.16 with an increase from base line of 13.4 ± 2.7% for the placebo group and 24.7 ± 3.9% for the creatine group. Other measures improved by creatine with a mean ES greater than 0 were for the amount of work accomplished, weight lifted, time, force production, cycle ergometer revolutions/min and power. The possible effect of creatine supplementation on multiple high intensity short duration bouts (<30 s) have shown an ES not statistically significant from 0. This would indicate that creatine supplementation might be useful to attenuate fatigue symptoms over multiple bouts of high-intensity, short duration exercise. The ES of creatine on anaerobic endurance exercise (>30 – 150s), primarily using the anaerobic glycolysis energy system, was 0.19 ± 0.05 with an improvement from baseline of 4.9 ± 1.5 % for creatine and -2.0 ± 0.6% for the placebo. The specific aspects of anaerobic endurance performance improved by creatine supplementation were work and power, both of which had a mean ES greater than 0. From the findings of this previous meta-analysis  it would appear that creatine supplementation has the most pronounced effect on short duration (<30s) high intensity intermittent exercises.
In the modern bodybuilding industry, the term "professional" generally means a bodybuilder who has won qualifying competitions as an amateur and has earned a "pro card" from their respective organization. Professionals earn the right to compete in competitions that include monetary prizes. A pro card also prohibits the athlete from competing in federations other than the one from which they have received the pro card. Depending on the level of success, these bodybuilders may receive monetary compensation from sponsors, much like athletes in other sports.
In a mouse model of allergin-induced asthma, where mice were sensitized by ovalbumin for three weeks and then given 500mg/kg creatine, supplementation induced an increase in asthmatic hyperresponsiveness to low but not high doses of methacholine. This hyperresponsiveness was associated with increased eosinophil and neutrophil infiltration into the lungs, and an increase in Th2 cell cytokines (IL-4 and IL-5) alongside an increase in IGF-1, which is known to influence this process. Interestingly, there was a nonsignificant increase in responsiveness in mice not sensitized to ovalbumin.
In otherwise healthy bodybuilders, supplementation of creatine at 5g either immediately before or after a weight training session (with no directive on days without training) over the course of four weeks noted that while both groups improved, there was no significant difference between groups overall. This null result has been found in another study with 0.1g/kg creatine thrice weekly over 12 weeks in otherwise healthy adults. It has been suggested that post-workout timing may be favorable (based on magnitude-based inference) since more individuals experience benefits with post-workout when compared to pre-workout despite no whole-group differences.
It is possible that females could benefit more than males due to a combined lower creatine kinase activity as well as having altered purine metabolism during depression, but no human comparative studies have been conducted yet. One rat study noted that creatine monohydrate at 2-4% of feed had 4% creatine able to exert anti-depressive and anxiolytic effects in female rats only.
When creatine supplementation is combined with heavy resistance training, muscle insulin like growth factor (IGF-1) concentration has been shown to increase. Burke et al  examined the effects of an 8 week heavy resistance training protocol combined with a 7 day creatine loading protocol (0.25 g/d/kg lean body mass) followed by a 49 day maintenance phase (0.06 g/kg lean mass) in a group of vegetarian and non-vegetarian, novice, resistance trained men and women. Compared to placebo, creatine groups produced greater increments in IGF-1 (78% Vs 55%) and body mass (2.2 Vs 0.6 kg). Additionally, vegetarians within the supplemented group had the largest increase of lean mass compared to non vegetarian (2.4 and 1.9 kg respectively). Changes in lean mass were positively correlated to the modifications in intramuscular total creatine stores which were also correlated with the modified levels of intramuscular IGF-1. The authors suggested that the rise in muscle IGF-1 content in the creatine group could be due to the higher metabolic demand created by a more intensely performed training session. These amplifying effects could be caused by the increased total creatine store in working muscles. Even though vegetarians had a greater increase in high energy phosphate content, the IGF-1 levels were similar to the amount observed in the non vegetarian groups. These findings do not support the observed correlation pattern by which a low essential amino acid content of a typical vegetarian diet should reduce IGF-1 production . According to authors opinions it is possible that the addition of creatine and subsequent increase in total creatine and phosphocreatine storage might have directly or indirectly stimulated production of muscle IGF-I and muscle protein synthesis, leading to an increased muscle hypertrophy .
Chwalbinska-Monteta  observed a significant decrease in blood lactate accumulation when exercising at lower intensities as well as an increase in lactate threshold in elite male endurance rowers after consuming a short loading (5 days 20 g/d) CM protocol. However, the effects of creatine supplementation on endurance performance have been questioned by some studies. Graef et al  examined the effects of four weeks of creatine citrate supplementation and high-intensity interval training on cardio respiratory fitness. A greater increase of the ventilatory threshold was observed in the creatine group respect to placebo; however, oxygen consumption showed no significant differences between the groups. The total work presented no interaction and no main effect for time for any of the groups. Thompson et al  reported no effects of a 6 week 2 g CM/d in aerobic and anaerobic endurance performance in female swimmers. In addition, of the concern related to the dosage used in these studies, it could be possible that the potential benefits of creatine supplementation on endurance performance were more related to effects of anaerobic threshold localization.
Researchers found that 5g of creatine four times daily for a week (loading) before sleep deprivation for 12-36 hours was able to preserve cognition during complex tasks of executive function at 36 hours only, without significant influence on immediate recall or mood. A similar protocol replicated the failure to improve memory and attention, but noted less reports of fatigue (24 hours) and less decline of vigor (24 hours) although other mood parameters were not measured.
You burn calories during strength training, and your body continues to burn calories after strength training (just like you do after aerobic exercise), a process called "excess post-exercise oxygen consumption" or EPOC, according to the American Council on Exercise. (13) When you do strength, weight, or resistance training, your body demands more energy based on how much energy you’re exerting (meaning the tougher you’re working, the more energy is demanded). That means more calories burned during the workout, and more calories burned after the workout, too, while your body is recovering to a resting state.
Older women with knee osteoarthritis given supplemental creatine at 20g for five days followed by 5g for the rest of the twelve week trial experienced improvements in stiffness (52% reduction), pain (45%), and physical function (41%) as assessed by WOMAC, despite no improvements in physical power output relative to placebo. This study paired supplementation and placebo with a mild exercise regimen.
Many people eat two or three meals a day and the occasional protein shake (when they remember), and then wonder why they're not putting on weight. To increase muscle mass, you have to have excess energy (calories and protein) in your system - supplied by regular small meals throughout the day. Most people have no idea how many calories they need. Do you? You may find that eating until you're full is not enough, especially if you're eating the wrong sort of calories (i.e. all carbs and no protein!). Protein is the priority followed by carbs then fat, but all are important and play a part in building mass and size.
One pilot study using 150mg/kg creatine monohydrate for a five day loading phase followed by maintenance (60mg/kg) for the remainder of the five weeks noted that supplementation was associated with fewer muscle symptoms and complaints alongside improved muscular function, yet a later trial trying to replicate the obsevations using 150mg/kg daily for five weeks noted the opposite, that creatine supplementation exacerbated symptoms.