Consequences of one-week creatine supplementation on creatine and creatinine levels in athletes' serum and urine (original) (raw)
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American Journal of Physiology-endocrinology and Metabolism, 1996
ingestion favorably affects performance and muscle metabolism during maximal exercise in humans. Am. J. Physiol. 271 (Endocrinol. Metab. 34): E31-E37, 1996.-Nine male subjects performed two bouts of 30-s maximal isokinetic cycling before and after ingestion of 20 g creatine (Cr) monohydrate/day for 5 days. Cr ingestion produced a 23.1 ? 4.7 mmol/kg dry matter increase in the muscle total creatine (TCr) concentration. Total work production during bouts 1 and 2 increased by-4%, and the cumulative increases in both peak and total work production over the two exercise bouts were positively correlated with the increase in muscle TCr. Cumulative loss of ATP was 30.7 2 12.2% less after Cr ingestion, despite the increase in work production. Resting phosphocreatine (PC,) increased in type I and II fibers. Changes in PCr before exercise bouts 1 and 2 in type II fibers were positively correlated with changes in PCr degradation during exercise in this fiber type and changes in total work production. The results suggest that improvements in performance were mediated via improved ATP resynthesis as a consequence of increased PCr availability in type II fibers.
Creatine supplementation and muscles: From metabolism to medical practice
Romanian Journal of Medical Practice, 2021
Creatine has become the most popular dietary supplement in sport and exercise physiology. In humans creatine is synthesized by the kidneys, pancreas and liver and transported mainly into brain, skeletal and cardiac muscle. Phosphocreatine is a high-energy content molecule, essential for the ADP to ATP conversion during intensive physical activity. Creatine and phosphocreatine are crucial in the energy shuttle system of high-energy phosphates between the mitochondrial ATP production and the cytosolic ATP consumption. Creatine supplementation increases lean body mass acting on myogenic regulatory factors. During muscular recovery, creatine supplementation regulates the regeneration process by reduction of muscle damage-induced inflammation and oxidative stress, activation and proliferation of satellite cells and regulation of calcium transport in muscle. The effects of creatine supplementation on muscle physiology are beneficial in anaerobic/aerobic exercises. In several muscle disord...
Creatine metabolism and the consequences of creatine depletion in muscle
Mol Cell Biochem, 1994
Currently, considerable research activities are focussing on biochemical, physiological and pathological aspects of the creatine kinase (CK) -phosphorylcreatine (PCr) -creatine (Cr) system (for reviews see ), but only little effort is directed towards a thorough investigation of Cr metabolism as a whole. However, a detailed knowledge of Cr metabolism is essential for a deeper understanding of bioenergetics in general and, for example, of the effects of muscular dystrophies, atrophies, CK deficiencies (e.g. in transgenic animals) or Cr analogues on the energy metabolism of the tissues involved. Therefore, the present article provides a short overview on the reactions and enzymes involved in Cr biosynthesis and degradation, on the organization and regulation of Cr metabolism within the body, as well as on the metabolic consequences of 3-guanidinopropionate (GPA) feeding which is known to induce a Cr deficiency in muscle. In addition, the phenotype of muscles depleted of Cr and PCr by GPA feeding is put into context with recent investigations on the muscle phenotype of 'gene knockout' mice deficient in the cytosolic muscle-type M-CK. (Mol Cell Biochem 133/134: 51-66, 1994).
2010
Young [n ϭ 5, 30 Ϯ 5 (SD) yr] and middle-aged (n ϭ 4, 58 Ϯ 4 yr) men and women performed single-leg knee-extension exercise inside a whole body magnetic resonance system. Two trials were performed 7 days apart and consisted of two 2-min bouts and a third bout continued to exhaustion, all separated by 3 min of recovery. 31 P spectra were used to determine pH and relative concentrations of P i , phosphocreatine (PCr), and -ATP every 10 s. The subjects consumed 0.3 g • kg Ϫ1 • day Ϫ1 of a placebo (trial 1) or creatine (trial 2) for 5 days before each trial. During the placebo trial, the middle-aged group had a lower resting PCr compared with the young group (35.0 Ϯ 5.2 vs. 39.5 Ϯ 5.1 mmol/kg, P Ͻ 0.05) and a lower mean initial PCr resynthesis rate (18.1 Ϯ 3.5 vs. 23.2 Ϯ 6.0 mmol • kg Ϫ1 • min Ϫ1 , P Ͻ 0.05). After creatine supplementation, resting PCr increased 15% (P Ͻ 0.05) in the young group and 30% (P Ͻ 0.05) in the middle-aged group to 45.7 Ϯ 7.5 vs. 45.7 Ϯ 5.5 mmol/kg, respectively. Mean initial PCr resynthesis rate also increased in the middle-aged group (P Ͻ 0.05) to a level not different from the young group (24.3 Ϯ 3.8 vs. 24.2 Ϯ 3.2 mmol • kg Ϫ1 • min Ϫ1). Time to exhaustion was increased in both groups combined after creatine supplementation (118 Ϯ 34 vs. 154 Ϯ 70 s, P Ͻ 0.05). In conclusion, creatine supplementation has a greater effect on PCr availability and resynthesis rate in middle-aged compared with younger persons.
Acta Physiologica Scandinavica, 1995
Seven male subjects performed repeated bouts of high-intensity exercise, on a cycle ergometer, before and after 6 d of creatine supplementation (20 g Cr H,O day-'). The exercise protocol consisted of five 6-s exercise periods performed at a fixed exercise intensity, interspersed with 30-s recovery periods (Part I), followed (40 s later) by one 10 s exercise period (Part 11) where the ability to maintain power output was evaluated. Muscle biopsies were taken from m. vastus lateralis at rest, and immediately after (i) the fifth 6 s exercise period in Part I and (ii) the 10 s exercise period in Part 11. In addition, a series of counter movement (CMJ) and squat (SJ) jumps were performed before and after the administration period. As a result of the creatine supplementation, total muscle creatine [creatine (Cr) + phosphocreatine (PCr)] concentration at rest increased from (mean SEM) 128.7 (4.3) to 151.5 (5.5) mmol kg-' dry wt (P < 0.05). This was accompanied by a 1.1 (0.5) kg increase in body mass (P < 0.05). After the fifth exercise bout in Part I of the exercise protocol, PCr concentration was higher [69.7 (2.3) vs. 45.6 (7.5) mmol kg-' dry wt, P < 0.051, and muscle lactate was lower [26.2 (5.5) vs. 44.3 (9.9) mmol kg-' dry wt, P < 0.051 after vs. before supplementation. In Part 11, after creatine supplementation, subjects were better able to maintain power output during the 10-s exercise period (P < 0.05). There was no change in jump performance as a result of the creatine supplementation (P > 0.05). These findings show that enhanced fatigue resistance during short duration highintensity exercise following creatine supplementation is associated with a greater availability of PCr and a lower accumulation of lactate in the muscle. The finding that jump performance was not enhanced suggests that short-term creatine feeding does not influence peak power output.
Does dietary creatine supplementation play a role in skeletal muscle metabolism and performance?
The American journal of clinical nutrition, 2000
Fatigue sustained during short-term, high-intensity exercise in humans is associated with the inability of skeletal muscle to maintain a high rate of anaerobic ATP production from phosphocreatine hydrolysis. Ingestion of creatine monohydrate at a rate of 20 g/d for 5-6 d was shown to increase the total creatine concentration of human skeletal muscle by approximately 25 mmol/kg dry mass, some 30% of this in phosphorylated form as phosphocreatine. A positive relation was then shown between muscle creatine uptake and improvements in performance during repeated bouts of maximal exercise. However, there is no evidence that increasing intake > 20-30 g/d for 5-6 d has any potentiating effect on creatine uptake or performance. In individuals in whom the initial total creatine concentration already approached 150 mmol/kg dry mass, neither creatine uptake nor an effect on phosphocreatine resynthesis or performance was found after supplementation. Loss of ATP during heavy anaerobic exercise...
Dietary Creatine Supplementation and Exercise Performance: Why Inconsistent Results?
Canadian Journal of Applied Physiology, 2002
Over the past few years there has been considerable interest in both the use of creatine (Cr) supplementation by athletes and the documentation of its effects by scientists. Some believe that this nitrogen-containing compound found in meat and fish has a performance-enhancing capability as important for brief intense exercise efforts as dietary carbohydrate is for activities where glycogen supplies limit performance. The mechanisms thought to be responsible for any ergogenic effect of acute (few d) Cr supplementation include: increased stores of muscle phosphocreatine (PCr), faster regeneration of PCr during exercise recovery, enhanced adenosine triphosphate (ATP) production from glycolysis secondary to increased hydrogen ion buffering, and/or possible shortened post contraction muscle relaxation time. With chronic (wk & mo) supplementation when combined with strength training, Cr may alter muscle protein metabolism directly (via decreasing protein breakdown or increasing synthesis)...
Ben Ayed BS 2014 trainURINARY CREATINE AT REST AND AFTER REPEATED SPRINTS IN ATHLETES: A PILOT STUDY
Creatine (Cr) is a naturally occurring amino acid-like compound provided by the diet and synthesized in the body mainly in the liver and kidney . Cr is then transported to tissues by a membrane creatine transporter (SLC6A8) . In humans, over 95% of the body Cr content is stored in skeletal muscle, where Cr or more specifically phosphocreatine (PCr) plays a major role in a muscle's ability to perform and maintain short duration, high intensity exercise [2].
Molecular and Cellular Biochemistry, 1998
Interest in creatine (Cr) as a nutritional supplement and ergogenic aid for athletes has surged over recent years. After cellular uptake, Cr is phosphorylated to phosphocreatine (PCr) by the creatine kinase (CK) reaction using ATP. At subcellular sites with high energy requirements, e.g. at the myofibrillar apparatus during muscle contraction, CK catalyzes the transphosphorylation of PCr to ADP to regenerate ATP, thus preventing a depletion of ATP levels. PCr is thus available as an immediate energy source, serving not only as an energy buffer but also as an energy transport vehicle. Ingestion of creatine increases intramuscular Cr, as well as PCr concentrations, and leads to exercise enhancement, especially in sprint performance. Additional benefits of Cr supplementation have also been noticed for high-intensity long-endurance tasks, e.g. shortening of recovery periods after physical exercise. The present article summarizes recent findings on the influence of Cr supplementation on energy metabolism, and introduces the Cr transporter protein (CreaT), responsible for uptake of Cr into cells, as one of the key-players for the multi-faceted regulation of cellular Cr homeostasis. Furthermore, it is suggested that patients with disturbances in Cr metabolism or with different neuro-muscular diseases may benefit from Cr supplementation as an adjuvant therapy to relieve or delay the onset of symptoms. Although it is still unclear how Cr biosynthesis and transport are regulated in health and disease, so far there are no reports of harmful side effects of Cr loading in humans. However, in this study, we report that chronic Cr supplementation in rats down-regulates in vivo the expression of the CreaT. In addition, we describe the presence of CreaT isoforms most likely generated by alternative splicing.
Creatine for Exercise and Sports Performance, with Recovery Considerations for Healthy Populations
Nutrients
Creatine is one of the most studied and popular ergogenic aids for athletes and recreational weightlifters seeking to improve sport and exercise performance, augment exercise training adaptations, and mitigate recovery time. Studies consistently reveal that creatine supplementation exerts positive ergogenic effects on single and multiple bouts of short-duration, high-intensity exercise activities, in addition to potentiating exercise training adaptations. In this respect, supplementation consistently demonstrates the ability to enlarge the pool of intracellular creatine, leading to an amplification of the cell’s ability to resynthesize adenosine triphosphate. This intracellular expansion is associated with several performance outcomes, including increases in maximal strength (low-speed strength), maximal work output, power production (high-speed strength), sprint performance, and fat-free mass. Additionally, creatine supplementation may speed up recovery time between bouts of intens...