Creatine is known to be present in the retina due to the expression of creatine kinase (CK) and the GAMT enzyme of creatine synthesis, which is also present in the mammalian retina. Creatine in the blood can be transported into the retina via the creatine transporter (confirmed in humans), and inhibiting transporter activity (by depleting the medium of chloride and sodium) reduces uptake by 80%. The fact that not all uptake was inhibited suggests that another transporter, such as the monocarboxylate transporter MCT12 (or SLC16A12), plays a role, perhaps moreso in the lens, where its levels were comparable to that of the major creatine transporter SLC6A8.
The creatine kinase system appears to be detectable in endothelial cells. Under basal conditions, creatine itself is expressed at around 2.85+/-0.62μM (three-fold higher than HUVEC cells). When incubating the medium with 0.5mM creatine, endothelial cells can take up creatine via the creatine transporter (SLC6A8) and increase both creatine (almost doubling) and phosphocreatine (nearly 2.5-fold) concentrations.
Most folks work a 9 to 5 position but if you’re not in the corporate world yet then odds are you’re a student with classes scattered throughout the day and it takes up the vast portion of your free time. That being said, you’re likely going to have to work out in the morning or the evening in order to fit in your session amidst the hectic commitments in your everyday life. Here are a few things to consider in regards to each time period:
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).
Gualano, B., de, Salles Painelli, V, Roschel, H., Lugaresi, R., Dorea, E., Artioli, G. G., Lima, F. R., da Silva, M. E., Cunha, M. R., Seguro, A. C., Shimizu, M. H., Otaduy, M. C., Sapienza, M. T., da Costa, Leite C., Bonfa, E., and Lancha Junior, A. H. Creatine supplementation does not impair kidney function in type 2 diabetic patients: a randomized, double-blind, placebo-controlled, clinical trial. Eur.J.Appl.Physiol 2011;111:749-756. View abstract.
After the ingestion of 5g creatine in otherwise healthy humans, serum levels of creatine were elevated from fasting levels (50-100µM) to 600-800µM within one hour after consumption. The receptor follows Michaelis-Menten kinetics with a Vmax obtained at concentrations higher than 0.3-0.4mmol/L, with prolonged serum concentrations above this amount exerting most of its saturation within two days.
In another case, supplements touted as "myostatin blockers" were formulated from a type of sea algae. In a test tube, they effectively blocked the activity of the protein myostatin, which inhibits muscular growth in the body. The supplement ads implied that they'd enable you to develop unprecedented levels of muscular growth, but as it turned out, they didn't actually work in the human body.
At the time, low-potency creatine supplements were available in Britain, but creatine supplements designed for strength enhancement were not commercially available until 1993 when a company called Experimental and Applied Sciences (EAS) introduced the compound to the sports nutrition market under the name Phosphagen. Research performed thereafter demonstrated that the consumption of high glycemic carbohydrates in conjunction with creatine increases creatine muscle stores.
One case study on a subject with a methylentetrahydrofolate reductase (MTHFR) 677TT homozygote, a relatively common genetic mutation known as “mild MTHFR deficiency,” which causes mild homocysteinemia, has seen benefits due to creatine supplementation where homocysteine was approximately halved (49% reduction) while CT heterozygotes and CC homozygotes (n=9) were unaffected. Additionally, one rat study suggested a possible role for creatine in reducing homocysteine levels in a model of high uric acid levels (model for end stage renal disease) but this was not replicated when investigated in humans.
An upper/lower split can last you forever. A lot of massive, strong powerlifters stick with that throughout their entire lifting careers. However, if you’re older and/or have some trouble recovering, you may prefer a push/pull/legs split that has you training everything directly once per week. This is how most famous bodybuilders have trained in the past and many still do.
For example, a 2015 review published in the peer-reviewed journal Applied Physiology, Nutrition, and Metabolism suggests that, for maximal muscle growth, people consume 25 to 35 grams of protein at breakfast, lunch and dinner. You'll find that amount of protein in a chicken breast, a cup of Greek yogurt with slivered almonds or about a three-quarter block of tofu.
Despite a possible decreasing creatine content in the muscles when maintenance is deemed suboptimal, the overall retention of weight and lean mass is merely additive over time. This is thought to be due to increases in skeletal muscle production (increase in body weight) compensating for the progressive declines in water and glycogen content (decreases in body weight).
Men who produce more testosterone are more likely to engage in extramarital sex. Testosterone levels do not rely on physical presence of a partner; testosterone levels of men engaging in same-city and long-distance relationships are similar. Physical presence may be required for women who are in relationships for the testosterone–partner interaction, where same-city partnered women have lower testosterone levels than long-distance partnered women.