Creatine synthesis primarily occurs in the liver and kidneys. On average, it is produced endogenously at an estimated rate of about 8.3 mmol or 1 gram per day in young adults. Creatine is also obtained through the diet at a rate of about 1 gram per day from an omnivorous diet. Most of the human body's total creatine and phosphocreatine stores are found in skeletal muscle, while the remainder is distributed in the blood, brain, and other tissues.
In fact, in one new study comparing the effects of aerobic exercise versus resistance training on the psychological health of obese adolescents, researchers found that people in the resistance group experienced significantly greater self-esteem and perceived strength over four weeks. But what’s most interesting is that the feeling of getting stronger — rather than any measurable gains — was all it took to give them a boost.
When many people think of someone with a high level of testosterone, they may picture a man loaded with strength, sexual prowess, and machismo. But while high-T has been correlated with all those things, it’s also been correlated with aggression, sexual misconduct, and violence. One of testosterone’s most common uses—as a performance-enhancing steroid—illustrates both sides of the hormone. Injecting steroids can be a quick way for athletes to dramatically improve performance, but the side effects can also be extreme, and can include excessive body hair growth, sexual dysfunction, and the hard-to-corral anger known as “roid rage.”
While this nonessential amino acid may not deliver earth-shattering PRs or extreme muscle growth, it does play an important role in repair and recovery. Glutamine works by removing excess ammonia, which can accumulate during intense exercise, helping to regulate your body's acid-base balance. Individuals who are engaged in heavy resistance training, two-a-day training splits, or are in a calorie deficit may benefit from the extra support of glutamine supplementation.