Creatine has been in use as an effective performance enhancing aid in many sports especially in track and field athletics for the past few decades. Since no harmful side effects have been found even at very large doses, its use is not prohibited by the governing bodies of sport (Maughan, 1999).
In mammals, creatine is synthesized naturally in the body from the amino acids, L-arginine, and glycine. In the kidney, the amino acids undergo L-arginine: glycine amidinotransferase-catalyzed reaction to give L-ornithine and guanidinoacetic acid. Guanidinoacetate is transported through the blood to liver where it is methylated to creatine in the presence of the enzyme S-adenosyl- L-methionine: N-guanidinoacetate methyltransferase.
Creatine is then supplied to creatine requiring tissues such as muscle and brain by the blood through an active transport system. In the muscles, creatine and phosphocreatine are converted to creatinine which is excreted by the kidneys into the urine (Wyss and Kaddurah-Daouk, 2000).
Approximately 94% of creatine is found in muscle tissue. Creatine stored in free and phosphorylated forms in skeletal muscles is important in maintaining a high ATP:ADP ratio during high-intensity exercise. Intense short-duration exercise results in phosphocreatine depletion from skeletal muscles. Inability to supply energy to rephosphorylate ADP to ATP, consequently leads to fatigue development and decline in physical performance (Chanutin, 1926; Hultman and Green haff, 1991; Greenhaff, 1997; Sahlin et al., 1998; Benzi and Ceci, 2001).
Creatine supplementation increases creatine and phosphocreatine concentrations in muscles, resulting in increased rate of ATP resynthesis and enhanced performance during high-intensity short-duration exercise (Sahlin et al., 1998; Benzi and Ceci, 2001).*(1)
ATP is critical for muscle contractions because it breaks the myosin-actin cross-bridge, freeing the myosin for the next contraction.*(2)
So, in simple words, ATP (Adenine Tri-Phosphate) is the body's energy source molecule bond. When creatine enters the body (or after it is produced by the body) it firsts binds with a phosphate molecule to form Creatine Phosphate. Every time we squeeze our muscles a chemical reaction occurs inside the muscle, energy release in the form of heat and the ATP bond breaks. What remains, ADP (adenine Di-phosphate), a molecule bond unable to give any chemical reaction (muscle fatigue). It needs to combine again with a phosphate molecule to form a new ATP bond (energy source). Creatine Phosphate provides this phosphate molecule (recharge) allowing us to train harder and longer.*(3)
*(1) Source: Effects of Amino Acid Derivativeson Physical, Mental, and Physiological Activities (FEBY LUCKOSE, MOHAN CHANDRA PANDEY, and KOLPE RADHAKRISHNA).
*(2) Source: (https://www.boundless.com/biology/textbooks/boundless-biology-textbook/the-musculoskeletal-system-38/muscle-contraction-and-locomotion-218/atp-and-muscle-contraction-826-12069/)
*(3) Source: Creatine: Fact And Fiction! by Layne Norton (http://www.bodybuilding.com/fun/layne13.htm)
In mammals, creatine is synthesized naturally in the body from the amino acids, L-arginine, and glycine. In the kidney, the amino acids undergo L-arginine: glycine amidinotransferase-catalyzed reaction to give L-ornithine and guanidinoacetic acid. Guanidinoacetate is transported through the blood to liver where it is methylated to creatine in the presence of the enzyme S-adenosyl- L-methionine: N-guanidinoacetate methyltransferase.
Creatine is then supplied to creatine requiring tissues such as muscle and brain by the blood through an active transport system. In the muscles, creatine and phosphocreatine are converted to creatinine which is excreted by the kidneys into the urine (Wyss and Kaddurah-Daouk, 2000).
Approximately 94% of creatine is found in muscle tissue. Creatine stored in free and phosphorylated forms in skeletal muscles is important in maintaining a high ATP:ADP ratio during high-intensity exercise. Intense short-duration exercise results in phosphocreatine depletion from skeletal muscles. Inability to supply energy to rephosphorylate ADP to ATP, consequently leads to fatigue development and decline in physical performance (Chanutin, 1926; Hultman and Green haff, 1991; Greenhaff, 1997; Sahlin et al., 1998; Benzi and Ceci, 2001).
Creatine supplementation increases creatine and phosphocreatine concentrations in muscles, resulting in increased rate of ATP resynthesis and enhanced performance during high-intensity short-duration exercise (Sahlin et al., 1998; Benzi and Ceci, 2001).*(1)
ATP is critical for muscle contractions because it breaks the myosin-actin cross-bridge, freeing the myosin for the next contraction.*(2)
The Cross-Bridge Muscle Contraction Cycle Source: Boundless. "ATP and Muscle Contraction".*(2)
So, in simple words, ATP (Adenine Tri-Phosphate) is the body's energy source molecule bond. When creatine enters the body (or after it is produced by the body) it firsts binds with a phosphate molecule to form Creatine Phosphate. Every time we squeeze our muscles a chemical reaction occurs inside the muscle, energy release in the form of heat and the ATP bond breaks. What remains, ADP (adenine Di-phosphate), a molecule bond unable to give any chemical reaction (muscle fatigue). It needs to combine again with a phosphate molecule to form a new ATP bond (energy source). Creatine Phosphate provides this phosphate molecule (recharge) allowing us to train harder and longer.*(3)
*(1) Source: Effects of Amino Acid Derivativeson Physical, Mental, and Physiological Activities (FEBY LUCKOSE, MOHAN CHANDRA PANDEY, and KOLPE RADHAKRISHNA).
*(2) Source: (https://www.boundless.com/biology/textbooks/boundless-biology-textbook/the-musculoskeletal-system-38/muscle-contraction-and-locomotion-218/atp-and-muscle-contraction-826-12069/)
*(3) Source: Creatine: Fact And Fiction! by Layne Norton (http://www.bodybuilding.com/fun/layne13.htm)
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