Creatine is most commonly used for improving exercise performance and increasing muscle mass in athletes and older adults. There is some science supporting the use of creatine in improving the athletic performance of young, healthy people during brief high-intensity activity such as sprinting. Because of this, creatine is often used as a dietary supplement to improve muscle strength and athletic performance. In the U.S., a majority of sports nutrition supplements, which total $2.7 billion in annual sales, contain creatine.
Supplementation of creatine at 5g daily alongside rehabilitation (after limb immobilization for two weeks while taking 20g daily) is associated with a preservation in GLUT4 levels, which were reduced during immobilization. During exercise rehabilitation, it increased to 40% above placebo.[330] This study failed to note an increase in GLUT4 in control, despite exercise normally doing so.[331][332] This effect is thought to be the result of the low frequency of activity. Thus, creatine was thought to augment the increase (insignificant due to low exercise) to significant levels.[330] In other studies, creatine was found to increase GLUT by approximately 30% relative to control, but this effect failed to reach statistical significance. This study did not issue an exercise protocol.[207]
The first open label trial on ALS failed to significantly alter lung function as assessed by FEV (when comparing the rate of decline pretreatment relative to treatment).[545] Creatine has elsewhere failed to benefit lung function at 5g daily for months relative to control[546] and failed to significantly attenuate the rate of lung function deterioration over 16 months at 10g daily[505] and 5g daily over nine months.[507]
Ladies!  The images of “bulky” women that you are conjuring up are from bodybuilding magazines. This is one of the biggest myth surrounding strength training. When I started strength training, I didn’t get bulky, I got lean, And I’m no outlier, I’m just one example of the rule: Women who strength train get strong and lean, not bulky.  Like Veronica, who got damn strong and certainly lean.
A: If your goal is the largest accrual of muscle mass possible then there may be some benefit to ingesting nutrients with a period of 30-60 minutes after your workout. Does this have to be a protein shake? No, but ideally it should be a meal lower in fat to enhance the digest rate of nutrients within the gastrointestinal tract. However, if you have just eaten a mixed macronutrient meal pre-workout then you should keep in mind that that meal is still likely digesting so there’s no need to throw down the weights after your last set and rush to your locker to slam a protein shake.
Supplementation of a loading phase of creatine has been noted to augment the increase in RBC levels of superoxide dismutase (SOD) from exercise, when measured immediately after, by 8.1%, but control groups increased to match within an hour.[299] Glutathione (normally decreases with exercise) and catalase (increases) were both unaffected,[299] and elsewhere in vitro red blood cells incubated with 3mM of creatine (within the supplemental range) is able to improve filterability (a measure of cell rheology, or fluid structure of the cell[300]) when RBC creatine was increased by 12.3% to reach 554µM.[301] This was thought to be due to reduced oxidative stress (assessed via MDA) in the red blood cells, which in the presence of 1-5mM creatine was progressively reduced by 20-41%.[301]

Another study demonstrated that females receiving 4 days of high-dose creatine intake (20 g/day) followed by low-dose creatine intake (5 g/day) during 10 weeks of resistance training (3hours/week) increased muscle PCr concentrations by 6%. Also, maximal strength of the muscle groups trained increased by 20-25%, maximal intermittent exercise capacity of the arm flexors increased by 10-25% and fat-free mass increased by 60% [11].

However, the basis of “take creatine after your workout” comes from a 2013 study published in the JISSN, which can be found here (open access too!). In this study, recreational male bodybuilders (19 men overall) were given five grams of creatine either before or after their workouts. They trained five days per week but were also directed to consume 5g on their rest days at any time they wanted. The workouts were fairly similar to most gym workouts, and the methodology (what they did and how they did it) suggests that the findings would apply to most weightlifters.
There are many potential reasons, but I am going to keep it simple and give you just two. The first and most common reason people suffer from underactive glutes or “glute amnesia” is due to lifestyle. Even when people train hard every day, if they spend the majority of the remainder of the day sitting down, then they are simply not using their glutes. And remember the old saying - if you don’t use it, you lose it. Unfortunately, this is just what happens with your glutes.
The gluteus maximus is one of three muscles of the glutes, and one of the largest muscles in the whole body. While many people think of the the “glutes” as one muscle (i.e, the butt muscle), they are actually a group of three muscles: the gluteus maximus, gluteus medius and gluteus minimus muscles. The gluteus maximus is the biggest of the gluteals and supports the other two glute muscles in various ways.
“Reg Park’s theory was that first you have to build the mass and then chisel it down to get the quality; you work on your body the way a sculptor would work on a piece of clay or wood or steel. You rough it out””the more carefully, the more thoroughly, the better”” then you start to cut and define. You work it down gradually until it’s ready to be rubbed and polished. And that’s when you really know about the foundation. Then all the faults of poor early training stand out as hopeless, almost irreparable flaws. [..]
^ Jump up to: a b Lazaridis I, Charalampopoulos I, Alexaki VI, Avlonitis N, Pediaditakis I, Efstathopoulos P, Calogeropoulou T, Castanas E, Gravanis A (2011). "Neurosteroid dehydroepiandrosterone interacts with nerve growth factor (NGF) receptors, preventing neuronal apoptosis". PLoS Biol. 9 (4): e1001051. doi:10.1371/journal.pbio.1001051. PMC 3082517. PMID 21541365.