What Do We Know About It Post 2

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There are gender differences in muscle type and mass. Males typically have more muscle mass and each single fiber is larger than those of a female. This difference accounts for greater uptake of creatine in males.

Independent of gender, an athlete with large, fast-acting muscle fibers is more apt to absorb more creatine into the muscle than an athlete with endurance type muscle fibers. This suggests that males with large sprinter type muscles will benefit the most from creatine supplementation.
What are the risks of using creatine supplementation in high school athletes?
There have been no studies of creatine supplementation in high school age athletes. The kidney and liver may be at risk because they must filter higher than normal levels of creatine, but this has not been shown in scientific studies. The liver does stop producing its portion of creatine during high level supplementation.

Some minor side effects of creatine supplementation, including muscle cramping, stomach upset and nausea have been reported, but not supported by scientific study.

An athlete who does not consume enough fluids while taking creatine can easily become dehydrated. A common measure of fluid loss is to measure body weight and drink fluids in a equal amount to match the weight lost. This measure of fluid loss does not work for people taking creatine because the body retains water inside the muscle. This can translate into little or no change in weight.

A better measure of hydration level for creatine users is to monitor urine output when supplementing with creatine to maintain urine output at the pre supplementation level to insure hydration levels are normal and blood volume is not compromised.
How is the creatine level increased in the muscle tissue?
The most health-conscious method of increasing muscle creatine is to use a loading phase where the athlete ingests 20-25 grams of creatine daily for four-to-five days.

The creatine is taken in four equal amounts by mixing 4-5 grams of creatine in 24-32 ounces of a 6-10 percent glucose and water solution. A maximal level of 160 mmol/kg (mmol is a measure of how concentrated the molecules of creatine are in the muscle cell) appears to be the upper limit of creatine concentration in the muscle cell. Any additional amount of creatine over 25 grams per day will be excreted in the urine.

It is important to measure urine output before starting the loading phase to insure adequate fluids are ingested to keep urine output at a normal level. It is common for urine output to drop during the loading phase, so a large volume of fluid helps maintain hydration for proper kidney function.

After the loading phase, the athlete reduces the creatine intake to 2-3 grams per day to maintain muscle creatine levels. Creatine uptake is enhanced by the concurrent use of carbohydrate.
Summary
The actual amount of creatine taken up by the body is determined by two things:

The initial level of creatine in the muscle.
The muscle type.

There is an upper limit to creatine loading that is dictated by the type of muscles an athlete inherits, and no amount of supplementation or training can change that inherited upper creatine level.

An upper limit of creatine stored by the body can be achieved using a loading phase (20-25 grams per day in four equal parts) for four-to-five days, followed by a maintenance phase (2-3 grams per day) matching the body’s natural requirement for creatine.

When taking creatine, fluid intake must be increased to maintain normal urine output and prevent dehydration.

Creatine supplementation has a potential for some athletes to improve performance. However, there is no scientific evidence to support its long-term safety, and the use of creatine has not been studied in high school age athletes with respect to performance enhancement or safety in the short or long term.