The effect of creatine monohydrate supplementation on sprint skating in ice-hockey players

AIM: Creatine monohydrate supplementation is beneficial for enhancing high-intensity exercise performance, especially activities that involve repeated sprints. Creatine monohydrate supplementation is common in ice-hockey players. The purpose of this study was to determine the effect of creatine monohydrate supplementation on sprint skating performance in Junior B and collegiate ice-hockey players. METHODS: Seventeen ice-hockey players were randomly assigned to receive creatine (0.3 g/kg body mass/day for 5 days) or placebo. Before and after supplementation players performed repeated sprints to exhaustion on a skating treadmill (repeated 10-s sprints; 30-s rest between sprints) while blood lactate was simultaneously collected. The time to exhaustion on the treadmill test was calculated as total amount of time, including partial intervals, before the player reached exhaustion. Players were also tested for peak torque and average power during knee extension/flexion (3 sets of 10 reps; 60-s rest between sets) on an isokinetic dynamometer at 60 degrees/s. RESULTS: The change in time to exhaustion from before to after supplementation averaged 20.6+/-7 s in the creatine group and 21.9+/-13 s in the placebo group, with no differences between groups. Likewise, there were no differences between groups for changes in isokinetic peak torque and average power. There were no differences between groups over time for blood lactate changes during the repeated sprints on the treadmill. CONCLUSIONS: We conclude that creatine was not effective for improving performance in these ice-hockey players.     

Creatine loading does not impact on stroke performance in tennis

The effect of acute creatine supplementation on stroke quality was investigated during simulated match play. Well-trained tennis players reported to the test center on two occasions. On each occasion they performed the Leuven Tennis Performance Test (LTPT) and a 70 m shuttle run (SHR). During 5 days prior to each test session they received in random order and according to a double-blind cross-over study design either oral creatine supplements (4 x 5 g per day) or placebo. The two experimental periods were separated by a 5-week washout period. Stroke quality was evaluated during the LTPT by means of registration of error rate and measurement of ball velocity and precision of lateral and longitudinal ball placement. Compared with placebo, creatine supplementation did not significantly impact on either power or precision of first and second services, baseline strokes in neutral and defensive rallies, and volleys. Shuttle run time was 19.87 +/- 0.30 sec during placebo versus 19.85 +/- 0.27 sec during creatine treatment. Acute creatine supplementation does not enhance stroke performance or sprint power in match-like conditions in elite tennis players.     

Effect of creatine supplementation on training for competition in elite swimmers

PURPOSE: The study was conducted to examine the effects of oral creatine supplementation on training for competition in 20 elite swimmers. METHODS: Subjects performed a maximal sprint test (8 x 50 yd (45.72 m), T1) before loading with creatine (Cr, 20 g.d Cr monohydrate for 5 d), 1 wk later (T2), and following a 22- to 27-wk period of training and competition (T3). Following T2, subjects supplemented with either Cr (3 g + glucose 7 g.d) or placebo (glucose 10 g.d; double blind) for the remainder of the 22- to 27-wk season and then both groups supplemented once more with 20 g.d Cr monohydrate for 5 d before their major competition. Venous and capillary blood samples were obtained pre- and posttest during the repeated sprint tests to determine blood metabolites and hormones. Competition times were recorded, and changes in subjects' best times were used to compare the effect of training and supplementation on competitive performance. RESULTS: Mean competition times in the Cr and control groups changed by+1.90 +/-1.91 and+0.72+/-1.64% for short course (SC, 25-m pool) and by+0.14+/-1.14 and -0.59+/-0.82% long course (LC, 50-m pool), respectively (Cr vs control, NS). No differences between groups were found in blood metabolites, although the human growth hormone (hGH) response to repeated sprints was blunted following Cr loading (T1, 30.42+/-14.60 and 28.95+/-18.27 microg.L; T2, 21.48+/-13.96 and 14.24+/-7.32 microg.L for Cr and control groups, respectively P<0.05). CONCLUSION: No statistically significant differences in performance were observed between groups after long-term maintenance during training, although small differences were observed that might be meaningful for elite performers.     

Effects of oral creatine supplementation on high intensity, intermittent exercise performance in competitive squash players.

The purpose of this study was to determine the effects of oral creatine supplementation on high intensity, intermittent exercise performance in competitive squash players. Nine squash players (mean +/- SEM VO2max = 61.9 +/- 2.1 ml x kg(-1) x min(-1); body mass = 73 +/- 3 kg) performed an on-court "ghosting" routine that involved 10 sets of 2 repetitions of simulated positional play, each set interspersed with 30 s passive recovery. A double blind, crossover design was utilised whereby experimental and control groups supplemented 4 times daily for 5 d with 0.075 g x kg(-1) body mass of creatine monohydrate and maltodextrine, respectively, and a 4 wk washout period separated the crossover of treatments. The experimental group improved mean set sprint time by 3.2 +/- 0.8% over and above the changes noted for the control group (P = 0.004 and 95% Cl = 1.4 to 5.1%). Sets 2 to 10 were completed in a significantly shorter time following creatine supplementation compared to the placebo condition (P < 0.05). In conclusion, these data support existing evidence that creatine supplementation improves high intensity, intermittent exercise performance. In addition, the present study provides new evidence that oral creatine supplementation improves exercise performance in competitive squash players.     

Effects of creatine supplementation on muscle power, endurance, and sprint performance

PURPOSE: To determine the effects of creatine (Cr) supplementation (20 g x d(-1) during 5 d) on maximal strength, muscle power production during repetitive high-power-output exercise bouts (MRPB), repeated running sprints, and endurance in handball players. METHODS: Nineteen trained male handball players were randomly assigned in a double-blind fashion to either creatine (N = 9) or placebo (N = 10) group. Before and after supplementation, subjects performed one-repetition maximum half-squat (1RM(HS) and bench press (1RM(BP)), 2 sets of MRPB consisting of one set of 10 continuous repetitions (R10) followed by 1 set until exhaustion (R(max)), with exactly 2-min rest periods between each set, during bench-press and half-squat protocols with a resistance equal to 60 and 70% of the subjects' 1RM, respectively. In addition, a countermovement jumping test (CMJ) interspersed before and after the MRPB half-squat exercise bouts and a repeated sprint running test and a maximal multistage discontinuous incremental running test (MDRT) were performed. RESULTS: Cr supplementation significantly increased body mass (from 79.4 +/- 8 to 80 +/- 8 kg; P < 0.05), number of repetitions performed to fatigue, and total average power output values in the R(max) set of MRPB during bench press (21% and 17%, respectively) and half-squat (33% and 20%, respectively), the 1RM(HS) (11%), as well as the CMJ values after the MRPB half-squat (5%), and the average running times during the first 5 m of the six repeated 15-m sprints (3%). No changes were observed in the strength, running velocity, or body mass measures in the placebo group during the experimental period. CONCLUSION: Short-term Cr supplementation leads to significant improvements in lower-body maximal strength, maximal repetitive upper- and lower-body high-power exercise bouts, and total repetitions performed to fatigue in the R(max) set of MRPB, as well as enhanced repeated sprint performance and attenuated decline in jumping ability after MRPB in highly trained handball players. Cr supplementation did not result in any improvement in upper-body maximal strength and in endurance running performance.     

Creatine supplementation delays onset of fatigue during repeated bouts of sprint running

In this study we have investigated the effect of creatine supplementation on performance of repeated sprint runs in well-trained young male handball players. The subjects participated in a test before supplementation (T1) and then received creatine (15 g/d) or placebo for five days before a second test was carried out (T2). Following T2, a low dose of creatine (2 g/d) or placebo was maintained for an additional nine days before the third test was performed (T3). The tests consisted of eight 40 m maximal sprint runs with a 25-s rest period between each sprint. Run time was reduced on the last three sprint runs after five days with high doses of creatine supplementation compared to T1 (P<0.05). Although the run time during the last three sprints was still significantly lower after supplementation of low doses of creatine compared to T1, analysis of variance showed only a tendency for an interaction between test day and random group (P = 0.14). No improvement was seen in the placebo group. Blood lactate was similar at T1 and T2 in the creatine and placebo groups. In conclusion, high doses of creatine supplementation improve performance during repeated sprint runs in well-trained handball players. Futher studies are needed to clarify whether low doses of creatine supplementation, after a period with supplementation of high doses, are able to maintain improved performance.     

The effects of creatine supplementation on selected factors of tennis specific training

Background

Creatine supplementation is popular among tennis players but it is not clear whether it actually enhances tennis performance.

Objectives

To examine the effects of creatine supplementation on tennis specific performance indices.

Methods

In a randomised, double blind design, 36 competitive male tennis players (24 creatine, mean (SD) age, 22.5 (4.9) years; 12 placebo, 22.8 (4.8) years) were tested at baseline, after six days of creatine loading, and after a maintenance phase of four weeks (14 creatine, 10 placebo). Serving velocity (10 serves), forehand and backhand velocity (three series of 5×8 strokes), arm and leg strength (bench press and leg press), and intermittent running speed (three series of five 20 metre sprints) were measured.

Results

Compared with placebo, neither six days nor five weeks of creatine supplementation had a significant effect on serving velocity (creatine: +2 km/h; placebo: +2 km/h, p = 0.90); forehand velocity (creatine: +4 km/h; placebo: +4 km/h, p = 0.80), or backhand velocity (creatine: +3 km/h; placebo: +1 km/h, p = 0.38). There was also no significant effect of creatine supplementation on repetitive sprint power after 5, 10, and 20 metres, (creatine 20 m: −0.03 m/s; placebo 20 m: +0.01 m/s, p = 0.18), or in the strength of the upper and lower extremities.

Conclusions

Creatine supplementation is not effective in improving selected factors of tennis specific performance and should not be recommended to tennis players.     

Reliability of a repeated-sprint test for field-hockey

The purpose of this study was to assess the reliability of a repeated-sprint test, specifically designed for field-hockey, as it was based directly on the time-motion analysis of elite level competition. The test consisted of 6 x 30-m over-ground sprints departing on 25s, with an active recovery (approximately 3.1-3.3 ms(-1)) between sprints. Ten highly trained, male, field-hockey players (mean+/-S.D.: age, 23+/-3 years; body mass, 78.1+/-7.1 kg) participated in this study. Following familiarisation, the subjects performed the repeated-sprint test on two occasions, 7 days apart. The reliability of the test variables was assessed by the typical error of measurement (TE). The total sprint time was very reliable (T(1): 26.79+/-0.76 s versus T2: 26.83+/-0.74 s), as the TE was 0.7% (95% CL, 0.5-1.2%). However, the percent sprint decrement was less reliable (T1: 5.6+/-0.9% versus T2: 5.8+/-1.0%), with the TE being 14.9% (95% CL, 10.8-31.3%). In summary, it is suggested that this field-hockey-specific, repeated-sprint test is very reliable when the results are presented as the total sprint time.     

Creatine supplementation improves sprint performance in male sprinters

The object of this study was to evaluate the effect of creatine (Cr) supplementation in well trained male sprinters. The study was performed as a single blind test on 18 sprinters at a local competition level. During the last two years a substantial part of their training had consisted of a series of maximal sprints with short rest periods to improve their fatigue resistance. The participants consumed either 20 g Cr+20 g glucose per day (Cr group, n=9) or 40 g glucose per day (placebo group, n=9), divided into 4 equal dosages. The effect of Cr on sprint performance was evaluated in two tests, 1 x 100 m sprint and an intermittent 6x60 m sprint. Cr supplementation increased the 100 m sprint velocity (11.68+/-0.27 s vs 11.59+/-0.31 s) and reduced the total time of 6 intermittent 60 m sprints (45.63+/-1.11 s vs 45.12+/-1.1 s), whereas no changes were observed in the placebo group. The sprint velocity was significantly increased in 5 out of 6 intermittent 60 m sprints. Venous blood was drawn 5 min after finishing the final intermittent 60 m run. Plasma lactate, Cr and serum creatinine (Crn) were all increased in the Cr group compared to presupplementation values; no changes were observed in the placebo group. The improved sprint performance suggests an increased availability of energy substrate for performing work, possibly as a result of increased skeletal muscle creatine phosphate (PCr).     

Aerobic and anaerobic power characteristics of Saudi elite soccer players

BACKGROUND: To assess the aerobic and anaerobic characteristics of Saudi elite soccer players, and to examine the interrelationship between measures of aerobic and anaerobic power in the elite soccer players. METHODS. PARTICIPANT: Twenty-three outfield elite soccer players representing the Saudi national team participated. Their means (+/- SD) for age, body mass, height and estimated fat % were: 25.2 +/- 2.3 years; 73.1 +/- 6.8 kg; 177.2 +/- 5.9 cm; and 12.3 +/- 2.7%, respectively. MEASURES: Cardiorespiratory parameters, including maximal oxygen uptake (V O2 max), were assessed by open-circuit spirometry during graded treadmill running. Anaerobic power measures were obtained using Wingate anaerobic test, and included peak power (PP), and average power for 5 sec (AP 5), 10 sec (AP 10), 20 sec (AP 20) and 30 sec (AP 30). RESULTS: Mean (+/-SD) values for V O2max in absolute and relative to body mass were 4.16 +/- 0.34 l x min-1 and 56.8 +/- 4.8 ml x kg-1 x min-1, respectively. Such V O2max value was 118% and 80% of those reported for Saudi college males and distance runners, respectively. The ventilatory anaerobic thereshold (Tvent) averaged 43.6 ml x kg-1 x min-1. There were no significant differences in V O2max and Tvent between players based on positions, although the midfielders and the centre-backs had the highest and the lowest individual values for both measures, respectively. Values (+/- SD) of PP and AP 30 were 873.6 +/- 141.8 W (11.88 +/- 1.3 W x kg-1), and 587.7 +/-55.4 W (8.02 +/- 0.53 W x kg-1), respectively. Only in absolute PP & AP 30 were the centre-backs significantly superior to the other players. In addition, V O2max was inversely related to PP (r = - 0.54; p < 0.05) and positively related to AP 30 (r = 0.45; p < 0.05). CONCLUSIONS: The aerobic power, expressed relative to body mass, of Saudi elite soccer players was in the lower range of values normally reported in the literatures for elite soccer players. Both PP and AP 30 were somewhat lower than values previously reported for elite soccer players from other countries.     

Effects of high dose oral creatine supplementation on anaerobic capacity of elite wrestlers

AIM: The purpose of this study was to investigate the effect of high dose oral creatine supplementation on anaerobic capacity of elite wrestlers. METHODS: Experimental design: comparative randomized design. Setting: Wingate anaerobic tests of the participants were taken at the Human Performance Laboratory of the Department of Physical Education and Sports in The Middle East Technical University, Ankara, Turkey. Participant: 20 active international level wrestlers participated (22 to 27 years old). Interventions: the daily dosage of creatine or placebo was divided into 4 equal amounts (5 gx4 = 20 g). Every 5 g of supplement was dissolved in 250 ml water and it was given to participants 1 hour before breakfast, lunch, dinner, and workout session. Measures: subjects underwent a 30-s Wingate Anaerobic tests until exhaustion in pre- and post-tests. After the pretest measurements were completed, participants were classified as creatine (Cr., n=10) and placebo (Pl., n=10) groups with regard to their average anaerobic power scores obtained during the test. RESULTS: Results of paired "t"-test revealed that there was no significant change in placebo group between pre- and post-test in average and peak anaerobic power. However, average and peak power mean scores obtained from post-test (8.123+/-0.448 W/kg and 10.523 +/-1.004 W/kg) were significantly (p<0.01) higher than pretest (7.233+/-0.483 W/kg and 8.992+/- 0.665 W/kg) for creatine group. Results of the independent "t"-test also indicated that the mean gained scores of creatine group in average and peak power were significantly higher than placebo group (p<0.01). CONCLUSION: This study demonstrates that short-term high dose oral creatine supplementation has an ergogenic effect on anaerobic capacity of elite wrestlers.     

The effects of creatine supplementation on performance during the repeated bouts of supramaximal exercise

AIM: The aim of this study was to investigate the effects of creatine supplementation on performance during the repeated bouts of supramaximal exercise. METHODS: Twenty-three untrained young males participated in the study. A double blind design was used to create the creatine and placebo groups. Wingate test was performed 5 times with 90 g x kg(-1) body weight load with 2-min intervals. Peak power, mean power (MP), fatigue index (FI) were calculated. Capillary blood samples for lactate analysis were taken during the initial rest period and soon after the fifth Wingate test. For 6 days the creatine group (n=12) ingested 5 g creatine monohydrate, the placebo group (n=11) a flavored drink without creatine monohydrate 4 times daily. On the 7th day, the Wingate tests were repeated, as was the 1st day. RESULTS: In the creatine group, MP in the 3rd and 4th Wingate test, in the placebo group FI in the 1st and 2nd Wingate test significantly increased. While the total power output obtained from the five Wingate tests increased 7.6% from 366.3+/-65 W to 394+/-67.1 W, there was no change in the placebo group. CONCLUSIONS: It is concluded that creatine supplementation enhances total power output during the repeated bouts of supramaximal exercise separated by short resting intervals.     

Few adverse effects of long-term creatine supplementation in a placebo-controlled trial

Although oral creatine supplementation is very popular among athletes, no prospective placebo-controlled studies on the adverse effects of long-term supplementation have yet been conducted. We performed a double-blind, placebo-controlled trial of creatine monohydrate in patients with the neurodegenerative disease amyotrophic lateral sclerosis, because of the neuroprotective effects it was shown to have in animal experiments. The purpose of this paper is to compare the adverse effects, and to describe the effects on indirect markers of renal function of long-term creatine supplementation. 175 subjects (age = 57.7 +/- 11.1 y) were randomly assigned to receive creatine monohydrate 10 g daily or placebo during an average period of 310 days. After one month, two months and from then on every fourth month, adverse effects were scored using dichotomous questionnaires, plasma urea concentrations were measured, and urinary creatine and albumin concentrations were determined. No significant differences in the occurrence at any time of adverse effects due to creatine supplementation were found (23 % nausea in the creatine group, vs. 24 % in the placebo group, 19 % gastro-intestinal discomfort in the creatine group, vs. 18 % in the placebo group, 35 % diarrhoea in the creatine group, vs. 24 % in the placebo group). After two months of treatment, oedematous limbs were seen more often in subjects using creatine, probably due to water retention. Severe diarrhoea (n = 2) and severe nausea (n = 1) caused 3 subjects in the creatine group to stop intake of creatine, after which these adverse effects subsided. Long-term supplementation of creatine did not lead to an increase of plasma urea levels (5.69 +/- 1.47 before treatment vs. 5.26 +/- 1.44 at the end of treatment) or to a higher prevalence of micro-albuminuria (5.4 % before treatment vs. 1.8 % at the end of treatment).     

Game performance and intermittent hypoxic training

Live high-train low altitude exposure simulated by hypoxic devices may improve athletic performance. In this study, intermittent normobaric hypoxia was achieved with the GO2altitude hypoxicator to determine its effects on sea level performance in rugby players. Ten players were randomly assigned to two groups. Players in each group received 14 sessions of either hypoxic (10-15% O(2)) or normoxic (21% O(2)) exposure at rest over 14 consecutive days in a single blind fashion. Various performance measures were obtained consecutively in a single testing session pre- and post-exposure. Effects of hypoxic exposure on maximum speed and sprint times were trivial (<1.0%) but unclear (90% likely range, +/-5% to +/-9%). In rugby simulation, hypoxic exposure produced impairments of peak power in two scrums (15%, +/-8%; 9%, +/-7%) and impairments of time in offensive sprints (7%, +/-8%) and tackle sprints (11%, +/-9%). Pending further research, rugby players would be unwise to use normobaric intermittent hypoxic exposure to prepare for games at sea level.     

Physiological responses to short-term exercise in the heat after creatine loading.

PURPOSE: This investigation was designed to examine the influence of creatine (Cr) supplementation on acute cardiovascular, renal, temperature, and fluid-regulatory hormonal responses to exercise for 35 min in the heat. METHODS: Twenty healthy men were matched and then randomly assigned to consume 0.3 g.kg(-1) Cr monohydrate (N = 10) or placebo (N = 10) for 7 d in a double-blind fashion. Before and after supplementation, both groups cycled for 30 min at 60-70% VO2(peak) immediately followed by three 10-s sprints in an environmental chamber at 37 degrees C and 80% relative humidity. RESULTS: Body mass was significantly increased (0.75 kg) in Cr subjects. Heart rate, blood pressure, and sweat rate responses to exercise were not significantly different between groups. There were no differences in rectal temperature responses in either group. Sodium, potassium, and creatinine excretion rates obtained from 24-h and exercise urine collection periods were not significantly altered in either group. Serum creatinine was elevated in the Cr group but within normal ranges. There were significant exercise-induced increases in cortisol, aldosterone, renin, angiotensin I and II, atrial peptide, and arginine vasopressin. The aldosterone response was slightly greater in the Cr (263%) compared with placebo (224%) group. Peak power was greater in the Cr group during all three 10-s sprints after supplementation and unchanged in the placebo group. There were no reports of adverse symptoms, including muscle cramping during supplementation or exercise. CONCLUSION: Cr supplementation augments repeated sprint cycle performance in the heat without altering thermoregulatory responses.     

Effect of creatine loading on long-term sprint exercise performance and metabolism

PURPOSE: This study examined whether creatine (Cr) supplementation could enhance long-term repeated-sprint exercise performance of approximately 80 min in duration. METHODS: Fourteen active, but not well-trained, male subjects initially performed 10 sets of either 5 or 6 x 6 s maximal bike sprints, with varying recoveries (24, 54, or 84 s between sprints) over a period of 80 min. Work done (kJ) and peak power (W) were recorded for each sprint, and venous blood was collected preexercise and on four occasions during the exercise challenge. Muscle biopsies (vastus lateralis) were obtained preexercise as well as 0 min and 3 min postexercise. Subjects were then administered either 20 g.d-1 Cr.H2O (N = 7) or placebo (N = 7) for 5 d. Urine samples were collected for each 24 h of the supplementation period. Subjects were then retested using the same procedures as in test 1. RESULTS: Total work done increased significantly (P < 0.05) from 251.7 +/- 18.4 kJ presupplementation to 266.9 +/- 19.3 kJ (6% increase) after Cr ingestion. No change was observed for the placebo group (254.0 +/- 10.4 kJ to 252.3 +/- 9.3 kJ). Work done also improved significantly (P < 0.05) during 6 x 6 s sets with 54-s and 84-s recoveries and approached significance (P = 0.052) in 5 x 6 s sets with 24-s recovery in the Cr condition. Peak power was significantly increased (P < 0.05) in all types of exercise sets after Cr loading. No differences were observed for any performance variables in the placebo group. Resting muscle Cr and PCr concentrations were significantly elevated (P < 0.05) after 5 d of Cr supplementation (Cr: 48.9%; PCr: 12.5%). Phosphocreatine levels were also significantly higher (P < 0.05) immediately and 3 min after the completion of exercise in the Cr condition. CONCLUSION: The results of this study indicate that Cr ingestion (20 g.day-1 x 5 d) improved exercise performance during 80 min of repeated-sprint exercise, possibly due to an increased TCr store and improved PCr replenishment rate.     

The effect of intramuscular iron injections on serum ferritin levels and physical performance in elite netballers

The purpose of this study was to determine the effect of iron supplementation by intramuscular injection on both serum ferritin (SF) levels and exercise performance in iron depleted, non-anaemic elite female netballers. Fifteen iron depleted (Serum Ferritin <40 ug x L(-1). Haemoglobin >125 g x L(-1)) subjects (19+/-3 y) first performed their routine test battery: a vertical jump test, a 10s power and 5x6s repeat sprint test on a cycle ergometer and a 20m multi-stage shuttle run. Subjects were matched on the basis of height, mass, and playing position and then assigned to either a Ferritin Group (FG) or Placebo Group (PG) (single blind design). Subjects then underwent a course of 5x2ml intramuscular injections of either Ferrum H (FG) or normal saline (PG) over a period of 8-10 days before repeating the blood and physical performance tests. Five and 10 days following supplementation, SF levels in the FG increased significantly from baseline levels (P<0.05) and were also significantly greater than levels measured in the PG (P<0.01). Haemoglobin levels remained unchanged in both groups. All test scores remained unchanged from baseline values and were not different between the two groups. These results demonstrate that a course of 5x2ml intramuscular iron injections significantly increased SF concentration within 2 weeks without increasing Hb levels, but this rapid elevation did not enhance the physical performance in selected tests of iron depleted, non-anaemic athletes.     

Creatine supplementation and sprint performance in soccer players

PURPOSE: This investigation examined the effects of creatine (Cr) supplementation on intermittent high-intensity exercise activities specific to competitive soccer. METHODS: On two occasions 7 d apart, 17 highly trained male soccer players performed a counter-movement jump test (CMJT), a repeated sprint test (RST) consisting of six maximal 15-m runs with a 30-s recovery, an intermittent endurance test (IET) consisting of forty 15-s bouts of high-intensity running interspersed by 10-s bouts of low-intensity running, and a recovery CMJT consisting of three jumps. After the initial testing session, players were evenly and randomly included in a CREATINE (5 g of Cr, four times per day for 6 d) or a PLACEBO group (same dosage of maltodextrins) using a double-blind research design. RESULTS: The CREATINE group's average 5-m and 15-m times during the RST were consistently faster after the intervention (0.95 +/- 0.03 vs 0.97 +/- 0.02 s, P < 0.05 and 2.29 +/- 0.08 vs 2.32 +/- 0.07 s, P = 0.07, respectively). Neither group showed significant changes in the CMJT or the IET. The CREATINE group's recovery CMJT performance relative to the resting CMJT remained unchanged postsupplementation, whereas it tended to decrease in the PLACEBO group. CONCLUSION: In conclusion, acute Cr supplementation favorably affected repeated sprint performance and limited the decay in jumping ability after the IET in highly trained soccer players. Intermittent endurance performance was not affected by Cr.     

Effects of oral creatine-pyruvate supplementation in cycling performance

A double-blind study was performed to evaluate the effects of oral creatine-pyruvate administration on exercise performance in well-trained cyclists. Endurance and intermittent sprint performance were evaluated before (pretest) and after (posttest) one week of creatine-pyruvate intake (Cr(pyr), 2 x 3.5 g x d-1, n = 7) or placebo (PL, n = 7). Subjects first performed a 1-hour time trial during which the workload could be adjusted at 5-min intervals. Immediately they did five 10-sec sprints interspersed by 2-min rest intervals. Tests were performed on an individual race bicycle that was mounted on an ergometer. Steady-state power production on average was about 235-245 W, which corresponded to blood lactate concentrations of 4-5 mmol x l -1 and heart rate in the range of 160-170 beats x min -1. Power outputs as well as blood lactate levels and heart rates were similar between Cr(pyr) and PL at all times. Total work performed during the 1-h trial was 872 +/- 44 KJ in PL versus 891 +/- 51 KJ in CR pyr. During the intermittent sprint test power peaked at about 800-1000 watt within 2-3 sec, decreasing by 15-20 % towards the end of each sprint. Peak and mean power outputs were similar between groups at all times. Peak lactate concentrations after the final sprint were approximately 11 mmol x l -1 in both groups during both the pretest and the posttest. It is concluded that one week of creatine-pyruvate supplementation at a rate of 7 g x d -1 does not beneficially impact on either endurance capacity or intermittent sprint performance in cyclists.