Abstracts
Blood Lipids
Blood lipids
A randomized, double-blind, placebo-controlled trial utilizing creatine as a potential lipid-lowering agent was conducted to determine plasma lipid, lipoprotein, glucose, urea nitrogen and creatinine profiles in men and women ranging in age fro 3 2 to 70 years.
Subjects (18 men and 16 women) with total cholesterol concentrations exceeding 200 mg/dl received either a creatine supplement (5 g of creatine plus 1 g of glucose) or a glucose placebo (6 g of glucose) for 56 days. Creatine and placebo were taken orally four times a day for 5 days and then twice a day for 51 days.
Minor reductions i plasma total cholesterol from baseline (233 +/- 9 mg/dl) of 6% and 5% occurred at weeks 4 and 8, respectively, before returning to baseline at week 12.
A trend towards reduced blood glucose levels was present in males given creatine monohydrate
Data suggest that creatine monohydrate may modulate lipid metabolism in certain individuals.
Earnest CP et al: High-performance capillary electrophoresis-pure creatine monohydrate reduces blood lipids in men and women. Clin Sci (Colch) 1996 Jul;91(1):113-8.
Body Water Content and Mass
Body Water Content and Mass
Creatine may increase body mass during strength training. This study examined the effect of creatine supplementation on the size of body water compartments and on isokinetic force levels during exercises. The body water content had increased but its relative volumes of the body water compartment were unchanged. Creatine increased the body mass by 2 kg, while the body mass of the placebo group remained unchanged. However both the creatine and placebo group increased the isokinetic force by 6%. Creatine may increase an individuals strength and body mass.
Francaux M, Poortmans JR: Effects of training and creatine supplement on muscle strength and body mass, Eur J Appl Physiol 1999 Jul;80 (2):165-8
Contractile Properties
Contractile Properties
Changes of contractile properties of extensor digitorum longus in response to hindlimb suspension and/or altered high-energy "phosphate" contents were studied in ats.
A reduction of high-energy "phosphates", especially phosphocreatine, was seen rats fed creatine analogue beta-guanidinopropionic acid (beta-GPA), but they re elevated after 10-days supplementation of creatine.
The "fatigue" resistance of creatine-depleted "muscle" was significantly improved, but tended to decrease by suspension and creatine supply, although it was still better that in the control diet group. It is indicated that the contractile properties of muscle are influenced by the high-energy phosphate content. It is also suggested the endurance capacity may be influenced by the "mitochondrial" respiratory apacity, but not necessarily by the levels of high-energy phosphates.
Watsuki, T. et al: Changes of contractile properties of extensor digitorum longus in response to creatine-analog administration and/or hindlimb suspension in rats. Jpn J Physiol. 1995, 45(6): 979 - 989.
Curvature constant parameter (Creatine)
Curvature Constant Parameter (W')
Creatine content in muscles may influence the curvature constant parameter (W') of the power-duration hyperbolic curve for cycle ergometry. The study determined the impact of oral creatine (Cr) supplementation on the outcome of the curvature constant parameter (W'). In this study, each individual underwent high-intensity exercise while taking creatine or placebo for 6 weeks. The outcome of the exercise showed that the W' had increased due to the creatine supplements.
Miura A, Kino F, Kajitani S, Sato H, Fukuba Y: The effect of oral creatine supplementation on the curvature constant parameter of the power-duration curve for cycle ergometry in humans, Jpn J Physiol 1999 Apr; 49(2):
169-174
Exercise Metabolism
Exercise Metabolism
This study examined the effect of:
(a) creatine supplementation on exercise metabolism and performance and
(b) changes in intramuscular total creatine stores following a 5 day supplementation "period" and a 28 day wash-out period.
Six men performed four exercise trials, each consisting of four 1 min cycling bouts, punctuated by 1 min of rest followed by a fifth bout to fatigue, all at a workload estimated to require II 5 or 12 5% V02,max. After three familiarization trials, one trial was conducted following a creatine monohydrate supplementation protocol (CREAT); the other after 28 d without creatine supplementation, in which the last 5 d involved placebo ingestion (CON). Intramuscular TCr was elevated (P 0.05)
The increase in TCr through creatine supplementation had no effect on performance when the creatine kinase system is not the principal energy supplier.
28 d without supplementation is a sufficient time to return intramuscular TCr stores to basal levels.
Febbraio MA et al: Effect of creatine supplementation on intramuscular TCr, metabolism and performance during intermittent, supramaximal exercise in humans. Acta Physiol Scand 1995 Dec;155(4):387-95.
Exercise Performance
Exercise Performance
The authors of this study suggest that creatine ingestion may enhance long-term sprint performance by increasing the levels of creatine and phosphocreatine found in resting muscle. Muscle biopsies and blood samples were taken from fourteen male subjects who performed one eighty-minute session of repeated maximal bike sprints, and their work done (kJ) and peak power (W) were also calculated during the session. The subjects performed a second eighty-minute challenge after receiving daily doses of placebo or
creatine-H2O (20g/day for five days). The group who received creatine supplementation increased their work done and power output in the second exercise challenge more than the control group, which may be due to the fact that they had increased stores of creatine and phosphocreatine available for short term energy.
Preen D, Dawson B, Goodman C, Lawrence S, Beilby J, Ching S: Effect of creatine loading on long-term sprint exercise performance and metabolism, Med Sci Sports Exerc 2001 May;33(5):814-21
These studies reveal that creatine (CR) supplementation may improve maximal strength and time during isometric exercise. Yet, the creatine supplementation only affects movements involving large muscle mass. During a clinical trial, ten active, young males (26 years old) took creatine and placebo supplementation and exercised for five days. Creatine supplementation remarkably increased both maximal isometric strength and prolonged length of time during exercises. CR substance may enhance athletic performance among professional and amateur athletes.
Urbanski RL, Vincent WJ, Yaspelkis III BB: Creatine supplementation differentially affects maximal isometric strength and time to fatigue in large and small muscle groups, Int J Sport Nutr 1999 Jun; 9(2): 136-45
Inborn Error
Inborn Error
In a patient with extrapyramidal movement disorder and extremely low creatinine concentrations in "serum" and urine, in vivo proton magnetic resonance spectroscopy disclosed a generalized depletion of creatinine in the "brain".
Oral substitution of "arginine", a "substrate" for creatine synthesis, resulted in an increase of brain guanidinoacetate as the immediate precursor of creatine but did not elevate cerebral creatine levels.
In contrast, oral substitution of creatine-monohydrate led to a significant increase of brain creatine, a decrease of brain guanidinoacetate, and a normalization of creatinine in serum and urine.
Partial restoration of cerebral creatine concentrations was accompanied by improvement of the patient's neurologic symptoms. This is the first report of a patient with complete creatine deficiency in the brain.
Stockler S et al: Creatine deficiency in the brain: a new, treatable inborn error of metabolism. Pediatr Res 1994 Sep;36(3):409-13.
Older Men and Exercise
Older Men and Exercise
In this study, oral creatine (Cr) supplementation may reduce muscle fatigue in men 60 years old or older, but it does not affect their body composition or strength. These men were given either creatine or placebo in different concentrations for a total of 20 days. They performed various exercises; their performance increased with creatine supplementation but decreased with placebo. Overall, creatine may increase time length and reduce risk of muscle fatigue during exercise among older men.
Rawson ES, Wehnert ML, Clarkson PM: Effects of 30 days of creatine ingestion in older men, Eur J Appl Physiol 1999 Jul; 80(2):139-44
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