Creatine Supplementation and Muscle Strength
Over the past 5-6 years there has been a growing awareness that creatine supplementation can increase muscle strength and mass (2,3). In 1998 sales of creatine in the Unites States are expected to reach $ 200 million (1).
Creatine is an amino acid that is stored in muscle in the form of creatine phosphate. During explosive or intensive exercise, creatine phosphate is broken down by a specific enzyme to yield creatine, plus phosphate, plus free energy. The free energy released from the breakdown of creatine phosphate is used to re-generate ATP, which is the fuel that powers muscle contraction (2).
The normal daily requirement for creatine is about 2 grams for a 70 kg. person. Animal protein (especially meats) provides half that amount and the other half is synthesized by the liver. A half-pound of raw meat contains about 1 gram of creatine.
A number of recent studies have demonstrated that short-term creatine supplementation increases creatine phosphate stores in skeletal muscle by 10% to 40% (3). This in turn leads to an increase in muscle mass, which is thought to occur from increased protein synthesis as the muscle lays down an increased number of contractile myofilaments (protein bands that contract and generate force). Increased muscular fluid retention may also participate in muscle mass gains (5, 6, 7).
It also appears that creatine supplementation may allow athletes to train harder (due to increased available energy for muscle concentration), which promotes strength gains, and increases muscle size due to hypertrophy (larger muscle fiber size) (2,3).
The established protocol for creatine supplementation involves a loading dosage of 20 to 25 grams per day for the first 5 to 7 days. Typically an athlete will mix a heaping teaspoon of creatine monohydrate crystals into a glass of juice to obtain about 5 grams of creatine. During the loading phase the athlete does this on 4 or 5 occasions throughout the day to attain an intake of 20-25 grams.
After the loading phase is completed the maintenance daily dosage is usually 5 to 10 grams per day. Recent reports suggest taking creatine with glucose (a simple carbohydrate) may increase the amount of creatine absorbed by the muscles. As such, some manufacturers combine creatine with carbohydrates in a premix product to help improve creatine delivery to muscles.
Several studies have shown that creatine supplementation improves performance in repeated bouts of high intensity strength work and repeated sprints, which are requirements for many sports (13, 14, 16, 17, 18).
Significant gains in strength and lean mass often occur in the first 6 weeks of creatine supplementation, when combined with proper training and diet.
In one study, college football players who took creatine supplements for 28 days during resistance and agility training had significant gains in lean mass when compared with players who took a placebo (15).
Individuals may vary in their response to creatine supplementation, but it is not uncommon to see a 5 to 10 lb. increase in weight within the first six weeks.
Approximately 80% of creatine studies have reported a performance-enhancing effect. This is quite impressive when you consider the fact that creatine is not structurally or functionally related to anabolic steroids, and creatine supplements are not banned by the International Olympic Committee or the National Collegiate Athletic Association. Creatine use is based on the same principle as carbohydrate loading in that an athlete is manipulating their dietary intake to optimize muscle creatine phosphate stores for more explosive power and enhanced performance.
As for the safety of creatine supplementation, a 1997 study showed that short-term creatine use (20 grams per day for 5 days) did not increase markers of kidney stress in five healthy men (21). However, individuals with pre-existing kidney disease should be cautious as evidenced by the development of kidney dysfunction in a 25 year old soccer player taking creatine who previously had been treated for focal segmental glomerulosclerosis of the kidney. His kidney function returned to normal when he stopped taking the creatine supplements.
For younger athletes, the safety of creatine supplementation has not yet been investigated. My feeling is that younger athletes should not use creatine, but rely on a proper diet and training to build their bodies during developmental years.
Overall creatine supplementation appears to be safe for healthy adults. It's a low molecular weight compound that is excreted in the kidneys by simple diffusion. In the maintenance phase athletes consume the amount of creatine generally found in the diet.
Due to its effectiveness in improving muscle energy stores and strength, creatine is now being studied as a therapy to reverse muscle wasting after heart surgery and to improve exercise capacity in patients who have chronic heart failure (10, 11).
Personally, I think creatine is here to stay. It works, and athletes notice differences in their lean muscle mass and strength almost right away. It's been studied for 5 or 6 years and scientific investigation around its use is still quite intensive.
Copyright 1998 Dr. James Meschino D.C., M.S. N.D.
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