Taking high doses of creatine might harm the kidneys. Some medications can also harm the kidneys. Taking creatine with medications that can harm the kidneys might increase the chance of kidney damage.
Some of these medications that can harm the kidneys include cyclosporine (Neoral, Sandimmune); aminoglycosides including amikacin (Amikin), gentamicin (Garamycin, Gentak, others), and tobramycin (Nebcin, others); nonsteroidal anti-inflammatory drugs (NSAIDs) including ibuprofen (Advil, Motrin, Nuprin, others), indomethacin (Indocin), naproxen (Aleve, Anaprox, Naprelan, Naprosyn), piroxicam (Feldene); and numerous others.
Fast twitch (or Type II fibers) fire very quickly, but also fatigue quickly, so they don’t last long. It gets a bit more complicated, because there are actually two types of fast twitch fibers. Type IIA fibers have some endurance qualities (used for things such as longer sprints). While Type IIX fibers are our “super fast” fibers, used only when a super short burst is needed (like a 100 m sprint or a really heavy lift).
Creatine supplementation has been noted to improve general wellbeing and health status (assessed by St George’s Respiratory questionnaire) of people with COPD over two weeks loading (17.1g daily with carbohydrates) and ten weeks of 5.7g maintenance. The studies that failed to find improvements with creatine supplementation on muscular performance also failed to find improvements in this rating scale, relative to placebo.
You've figured out the exercises you should be doing, but what about the number of sets and repetitions? Your decision should be based on your goals. The American College of Sports Medicine recommends 8-12 reps for muscular strength and 10-15 reps for muscular endurance. They also recommend at least 1 set of each exercise to fatigue although you'll find that most people perform about 2-3 sets of each exercise. In general:
However, caffeine does not negate the benefits of creatine loading when not coingested, but just taken before exercise in the same dosage. This result indicates that loading creatine without caffeine on a daily basis, but saving caffeine for select workouts, may be an effective strategy, as creatine does not adversely affect caffeine’s ergogenic effects and may enhance creatine’s effectiveness in anaerobic exertion if the two compounds are alternated.
Don’t take sets to the point of failure—where you absolutely can’t perform another rep. You should never get to where you’re turning purple and screaming like you’re getting interviewed by “Mean” Gene Okerlund before WrestleMania. Most of the time, you want to end your sets two reps before total failure. Not sure when that is? The moment your form breaks down, or you’re pretty sure it’s going to break down, end the set.
In regard to the blood brain barrier (BBB), which is a tightly woven mesh of non-fenestrated microcapillary endothelial cells (MCECs) that prevents passive diffusion of many water-soluble or large compounds into the brain, creatine can be taken into the brain via the SLC6A8 transporter. In contrast, the creatine precursor (guanidinoacetate, or GAA) only appears to enter this transporter during creatine deficiency. More creatine is taken up than effluxed, and more GAA is effluxed rather than taken up, suggesting that creatine utilization in the brain from blood-borne sources is the major source of neural creatine. However, “capable of passage” differs from “unregulated passage” and creatine appears to have tightly regulated entry into the brain in vivo. After injecting rats with a large dose of creatine, creatine levels increased and plateaued at 70uM above baseline levels. These baseline levels are about 10mM, so this equates to an 0.7% increase when superloaded. These kinetics may be a reason for the relative lack of neural effects of creatine supplementation in creatine sufficient populations.