Ben Ayed BS 2014 trainURINARY CREATINE AT REST AND AFTER REPEATED SPRINTS IN ATHLETES: A PILOT STUDY (original) (raw)
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URINARY CREATINE AT REST AND AFTER REPEATED SPRINTS IN ATHLETES: A PILOT STUDY
Biology of Sport, 2014
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].
Nutrition, 2002
We measured the effect of 3 d of creatine (Cr) supplementation on repeated sprint performance and thigh muscle volume in elite power athletes. METHODS: Ten male (mean Ϯ standard deviation of body mass and percentage of fat (81.1 Ϯ 10.5 kg and 9.8 Ϯ 3.5) and ten female (58.4 Ϯ 5.3 kg and 15.0 Ϯ 3.4) athletes were matched for sex and 10-s cycle sprint scores, paired by rank, and randomly assigned to the Cr or placebo (P) group. Subjects completed six maximal 10-s cycle sprints interspersed with 60 s of recovery before and after 3 d of Cr (0.35 g/kg of fat-free mass) or P (maltodextrin) ingestion. Before and after supplementation, 10 contiguous transaxial images of both thighs were obtained with magnetic resonance imaging. RESULTS: Cr supplementation resulted in statistically significant increases in body mass (0.9 Ϯ 0.1 kg, P Ͻ 0.03), total work during the first sprint (P Ͻ 0.04), and peak power during sprints 2 to 6 (P Ͻ 0.10). As expected, total work and peak power values for males were greater than those for their female counterparts during the initial sprint (P Ͻ 0.02); however, the reverse was true during the last three sprints (P Ͻ 0.01). Imaging data showed a 6.6% increase in thigh volume in five of six Cr subjects (P ϭ 0.05). CONCLUSION: These data indicate that 3 d of Cr supplementation can increase thigh muscle volume and may enhance cycle sprint performance in elite power athletes; moreover, this effect is greater in females as sprints are repeated.
Effect of creatine supplementation on sprint exercise performance and muscle metabolism
Journal of Applied Physiology
The aim of the present study was to examine the effect of creatine supplementation (CrS) on sprint exercise performance and skeletal muscle anaerobic metabolism during and after sprint exercise. Eight active, untrained men performed a 20-s maximal sprint on an air-braked cycle ergometer after 5 days of CrS [30 g creatine (Cr) + 30 g dextrose per day] or placebo (30 g dextrose per day). The trials were separated by 4 wk, and a double-blind crossover design was used. Muscle and blood samples were obtained at rest, immediately after exercise, and after 2 min of passive recovery. CrS increased the muscle total Cr content (9.5 ± 2.0%, P < 0.05, mean ± SE); however, 20-s sprint performance was not improved by CrS. Similarly, the magnitude of the degradation or accumulation of muscle (e.g., adenine nucleotides, phosphocreatine, inosine 5′-monophosphate, lactate, and glycogen) and plasma metabolites (e.g., lactate, hypoxanthine, and ammonia/ammonium) were also unaffected by CrS during ex...
Guanidino Compounds in Biology and Medicine, 2003
Creatine has been reported to be an effective ergogenic aid for athletes. However, concerns have been raised regarding the long-term safety of creatine supplementation. This study examined the effects of long-term creatine supplementation on a 69item panel of serum, whole blood, and urinary markers of clinical health status in athletes. Over a 21-month period, 98 Division IA college football players were administered in an open label manner creatine or non-creatine containing supplements following training sessions. Subjects who ingested creatine were administered 15.75 g/day of creatine monohydrate for 5 days and an average of 5 g/day thereafter in 5-10 g/day doses. Fasting blood and 24-h urine samples were collected at 0, 1, 1.5, 4, 6, 10, 12, 17, and 21 months of training. A comprehensive quantitative clinical chemistry panel was determined on serum and whole blood samples (metabolic markers, muscle and liver enzymes, electrolytes, lipid profiles, hematological markers, and lymphocytes). In addition, urine samples were quantitatively and qualitative analyzed to assess clinical status and renal function. At the end of the study, subjects were categorized into groups that did not take creatine (n = 44) and subjects who took creatine for 0-6 months (mean 4.4 ± 1.8 months, n = 12), 7-12 months (mean 9.3 ± 2.0 months, n = 25), and 12-21 months (mean 19.3 ± 2.4 months, n = 17). Baseline and the subjects' final blood and urine samples were analyzed by MANOVA and 2 ´ 2 repeated measures ANOVA univariate tests. MANOVA revealed no significant differences (p = 0.51) among groups in the 54-item panel of quantitative blood and urine markers assessed. Univariate analysis revealed no clinically significant interactions among groups in markers of clinical status. In addition, no apparent differences were observed among groups in the 15-item panel of qualitative urine markers. Results indicate that long-term creatine supplementation (up to 21-months) does not appear to adversely effect markers of health status in athletes undergoing intense training in comparison to athletes who do not take creatine. (Mol Cell Biochem 244: [95][96][97][98][99][100][101][102][103][104] 2003)
Effects of creatine supplementation on the performance and body composition of competitive swimmers
The Journal of Nutritional Biochemistry, 2004
Creatine has become a popular nutritional supplement among athletes. Recent research has also suggested that there may be a number of potential therapeutic uses of creatine. This paper reviews the available research that has examined the potential ergogenic value of creatine supplementation on exercise performance and training adaptations. Review of the literature indicates that over 500 research studies have evaluated the effects of creatine supplementation on muscle physiology and/or exercise capacity in healthy, trained, and various diseased populations. Short-term creatine supplementation (e.g. 20 g/day for 5-7 days) has typically been reported to increase total creatine content by 10-30% and phosphocreatine stores by 10-40%. Of the approximately 300 studies that have evaluated the potential ergogenic value of creatine supplementation, about 70% of these studies report statistically significant results while remaining studies generally report non-significant gains in performance. No study reports a statistically significant ergolytic effect. For example, short-term creatine supplementation has been reported to improve maximal power/strength (5-15%), work performed during sets of maximal effort muscle contractions (5-15%), single-effort sprint performance (1-5%), and work performed during repetitive sprint performance (5-15%). Moreover, creatine supplementation during training has been reported to promote significantly greater gains in strength, fat free mass, and performance primarily of high intensity exercise tasks. Although not all studies report significant results, the preponderance of scientific evidence indicates that creatine supplementation appears to be a generally effective nutritional ergogenic aid for a variety of exercise tasks in a number of athletic and clinical populations. (Mol Cell Biochem 244: [89][90][91][92][93][94] 2003)
The Biomechanic Origin of Sprint Performance Enhancement after One-Week Creatine Supplementation
Japanese Journal of Physiology, 2000
Creatine (Cr) is an endogenous as well as an exogenous compound related with high-energy metabolism . During muscular exercise, ATP is directly used for mechanical contractions of actin and myosin filaments. The fastest anaerobic metabolic pathway to regenerate ATP is the utilization of phosphocreatine (PCr). However, the total pool of PCr is limited. The ingestion of exogenous Cr consequently increases intracellular Cr and PCr concentrations . This increase could therefore theoretically improve muscular performance during anaerobic exercises. In parallel, an increase in body weight is also usually reported . The exact origin of the ergogenic effect of Cr supplementation is unclear; in particular, the mechanism behind improvement in running performance. Experimentally, many studies have highlighted an ergogenic effect of Cr during anaerobic exercises, but some authors have shown no effect on anaerobic performance and even a negative effect .
Clinical Science, 2003
Most research on creatine has focused on short-term creatine loading and its effect on highintensity performance capacity. Some studies have investigated the effect of prolonged creatine use during strength training. However, studies on the effects of prolonged creatine supplementation are lacking. In the present study, we have assessed the effects of both creatine loading and prolonged supplementation on muscle creatine content, body composition, muscle and whole-body oxidative capacity, substrate utilization during submaximal exercise, and on repeated supramaximal sprint, as well as endurance-type time-trial performance on a cycle ergometer. Twenty subjects ingested creatine or a placebo during a 5-day loading period (20 g : day − 1 ) after which supplementation was continued for up to 6 weeks (2 g : day − 1 ). Creatine loading increased muscle free creatine, creatine phosphate (CrP) and total creatine content (P 0.05). The subsequent use of a 2 g : day − 1 maintenance dose, as suggested by an American College of Sports Medicine Roundtable, resulted in a decline in both the elevated CrP and total creatine content and maintenance of the free creatine concentration. Both short-and long-term creatine supplementation improved performance during repeated supramaximal sprints on a cycle ergometer. However, whole-body and muscle oxidative capacity, substrate utilization and time-trial performance were not affected. The increase in body mass following creatine loading was maintained after 6 weeks of continued supplementation and accounted for by a corresponding increase in fat-free mass. This study provides definite evidence that prolonged creatine supplementation in humans does not increase muscle or whole-body oxidative capacity and, as such, does not influence substrate utilization or performance during endurance cycling exercise. In addition, our findings suggest that prolonged creatine ingestion induces an increase in fat-free mass.