Creatine supplementation appears to attenuate decreases in GLUT4 expression seen with immobility and may increase GLUT4 expression during exercise. While it seems capable of increasing GLUT4 during resting conditions, it has failed to reach significance, suggesting that creatine supplementation works best with some stimuli associated with exercise.
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.
Weight training aims to build muscle by prompting two different types of hypertrophy: sarcoplasmic and myofibrillar. Sarcoplasmic hypertrophy leads to larger muscles and so is favored by bodybuilders more than myofibrillar hypertrophy, which builds athletic strength. Sarcoplasmic hypertrophy is triggered by increasing repetitions, whereas myofibrillar hypertrophy is triggered by lifting heavier weight. In either case, there is an increase in both size and strength of the muscles (compared to what happens if that same individual does not lift weights at all), however, the emphasis is different.
While the number of reps you do per set is important, of equal importance is the total number of reps you do per muscle group. The National Strength and Conditioning Association has determined that, to maximize growth, you need approximately 20–70 total reps per muscle group. Depending on which end of a rep range you’re working, this can be done in one session or over a few days (a training week, for instance), but that’s the spread you need to cover to see gains.
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.
As the name implies, the muscle power objective can be pursued if you want to achieve maximum size in your muscles or if you want them to be explosively strong (i.e. very powerful for short bursts at a time). In order to develop muscles this way you'll want to use no more than 3 sets in which no more than 8 reps are used. Muscle size and power is often used for muscles that are prominently displayed on the human figure, such as the pectorals, or the biceps and triceps.