Table 1

Summary of studies investigating the
ergogenic value of creatine supplementation on muscle bioenergetics and exercise performance.



Reference

Subjects & Supplement Dose

Tests Performed

Results
Greenhaff et al. (4)
10 male and 2 female subjects performed pre-testing and then ingested 20 g/d of creatine for 5-d.
Subjects underwent 20 intense electrically evoked isometric contractions (1.6-s contraction with 1.6-s rest) of the quadriceps or tibialis anterior with limb blood flow occluded. Biopsy samples from the vastus lateralis or 31P MRS were determined prior to and at 40-s and 137-s of recovery.
Creatine supplementation resulted in a 20% increase in recovery muscle PCr determined by biopsy (55 to 67 mmol/kg dry mass) and an 11% higher PCr concentration with MRS (77 to 85 mmol/kg dry mass).
Harris et al. (5)
12 male and 5 female active and inactive subjects ingested between 20 and 30 g/d of creatine for 4.5-, 7-, 10-, or 21-d (taken on alternate days).
Subjects had resting muscle TCr, ATP, and PCr determined prior to and following creatine supplementation. Five subjects performed one legged cycle ergometry for 60-min so that the effects of exercise following creatine supplementation on TCr, ATP, and PCr could be determined. Blood samples were obtained to determine creatine levels and standard hematological profiles. Urinary creatine excretion was also determined.
Dosages of 5 g of creatine resulted in peak plasma creatine concentrations at 60-min following administration. Repeated doses of 5 g every 2-h for 8-h maintained high plasma creatine levels. Creatine supplementation increased TCr by 20% (127 to 149 mmol/kg dry mass), PCr by 36% (67 to 91 mmol/kg dry mass) with no effect on ATP levels. The greatest increases occurred in subjects with lower initial TCr content. Exercise with creatine supplementation resulted in significantly greater muscle TCr (9%). Urinary analysis revealed that creatine uptake was greatest during the first 2-d. No significant effects were observed in standard clinical blood profiles.
Balsom et al. (8)
7 male subjects performed pre-supplementation tests and were then administered 20 g/d of creatine for 6-d.
5 x 6-s cycle ergometer sprints with 30-s rest recovery followed 40-s later with 1 x 10-s maximal effort sprint. Muscle biopsies taken at rest, after the fifth 6-s sprint, and following the 10-s sprint. A series of counter movement squat jumps were performed prior to and following supplementation.
Body mass increased by 1.1 kg. Total muscle creatine content significantly increased (129 to 152 mmol/kg dry wt). Following creatine supplementation, muscle PCr concentration was higher after the 5th sprint (70 vs. 46 mmol/kg dry wt) and muscle lactate was lower (26 vs 44 mmol/kg dry wt) following creatine supplementation. Work output was significantly greater in the 10-s sprint following creatine supplementation. No differences were observed in jump performance.
Febbraio et al. (9)
6 males subjects performed pre-supplementation tests and then ingested 20 g/d of creatine for 5-d. Subjects then observed a 23-d washout period and began ingesting a placebo for 5-d.
Subjects performed 4 x 60-s cycle ergometer sprints with 60-s recovery between sprints followed by cycling to exhaustion at a work rate equivalent to 115-120% of VO2max. Intramuscular TCr, PCr, ATP, ADP, AMP, inosine 5'-monophosphate (IMP), ammonia, lactate and glycogen levels were determined prior to and following exercise.
Creatine supplementation resulted in significant increases in TCr and PCr concentrations with no effect on ATP, ADP, AMP, IMP, NH3, lactate, or glycogen levels. Creatine supplementation did not affect time to exhaustion during the 5th sprint trial. TCr stores returned to normal within the 28-d washout period.
Green et al. (10)
21 male subjects ingested 20 g/d of creatine or 20 g/d of creatine with 400 g/d of carbohydrate for 5-d.
Prior to and following supplementation, TCr and glycogen concentrations were determined.
Creatine supplementation increased TCr by 18% (122 to 143 mmol/kg dry mass) and did not affect glycogen content (365 to 366 mmol/kg dry mass). Ingestion of glucose alone resulted in a 4% decrease in TCr (130 to 124 mmol/kg dry mass) and a 22% increase in glycogen content (338 to 441 mmol/kg dry mass). Ingestion of glucose with creatine resulted in significantly greater increases in TCr (124 to 158 mmol/kg dry mass or 27%) and muscle glycogen content (331 to 489 mmol/kg dry mass or 48%).
Green et al. (11)
22 male subjects were administered either: a) a normal diet, no exercise, 20 g/d of creatine with a non-glucose placebo; b) a high carbohydrate diet, no exercise, 20 g/d of creatine and 93 g/d of carbohydrate; c) a high carbohydrate, exercise (60-min of cycling at 70% VO2max), 20 g/d of creatine with 93 g/d of carbohydrate; or d) a normal diet, no exercise, and a placebo.
Plasma creatine, serum insulin, and 24 urinary excretion of creatine were determined on days 1 and 3 of study to evaluate creatine retention.
Results showed that carbohydrate ingestion augmented creatine retention due to a greater increase in insulin levels and that exercise did not provide further benefit.
Greenhaff et al. (12)
8 active but not highly trained male subjects ingested 20 g/d of creatine for 5-d.
Prior to and following supplementation, muscle biopsies were taken at rest and following 0, 20, 60, 120-s recovery from electrically evoked isometric contractions (20 x 1.6-s contractions with 1.6-s rest recovery between contractions).
Subjects had a significant increase in body mass (1.6 kg), resting TCr (15%), and PCr resynthesis was similar at 60-s recovery but 42% greater following 120-s recovery following creatine supplementation. There was some evidence that not all subjects responded to creatine supplementation.
Hultman et al. (13)
31 male subjects ingested either 20 g/d of creatine for 6-d followed by ingesting 2 g/d for 22 days or 3 g/d of creatine for 28-d.
Muscle creatine content and urinary excretion of creatine was determined.
Ingesting 20 g/d of creatine for 6-d resulted in a 20% increase in TCr. Ingesting 2 g/d of creatine thereafter served to maintain muscle TCr levels. However, TCr levels declined within 30-d without ingesting the 2 g/d maintenance dose. Ingesting 3 g/d of creatine resulted in a gradual increase muscle TCr approaching loading levels in 28-d. Urinary excretion paralleled intake.
Kurosawa et al. (14)
4 male and 1 female subject consumed 30 g/d of creatine for 14-d.
Subjects performed low and high intensity grip exercise in which blood creatine concentration and forearm PCr concentrations were determined using 31P MRS. In addition, muscle biopsies were obtained to measure muscle PCr and ATP concentrations. Subjects then began supplementation and performed grip exercise training with their dominant arm (1 contraction at 30% of maximal voluntary contraction until exhaustion) 6 times per day for 14-d. Pre-tests were then repeated following supplementation.
Creatine supplementation increased blood creatine concentrations (47 fold) and also increased muscle creatine concentration relative to -ATP levels by 11% in the non-training and 23% in the trained group. Creatine supplementation increase high intensity grip strength performance in non-trained (20%) and trained groups (35%). No significant differences were observed in time to exhaustion during the low intensity muscle contractions although times were increased by 23% and 96% for the untrained and trained arms, respectively.
Lemon et al. (15)
7 active male subjects ingested either 20 g/d of creatine or a placebo for 5-d. Subjects then observed a 35-d washout period and then repeated the experiment ingesting the alternate supplement.
Subjects performed 20 x 30-s maximal effort isometric muscle contractions (plantar flexion) with 16-s rest recovery following ingesting creatine and the placebo for 5-d. PCr and ATP concentrations during exercise were determined using 31P MRS. Blood samples were obtained to measure serum creatine.
Creatine supplementation increased body mass by 1.3 kg, PCr/ATP by 8% (p=0.10), total force produced by 11%, and maximal force by 10%. Calculated rates of oxidative phosphorylation and glycolysis were increased with creatine supplementation. In addition, there was some evidence that the 35-d washout was not long enough for TCR levels to return to normal.
Ruden et al. (16)
5 female and 4 male subjects ingested 20 g/d of creatine and a placebo for 4-d separated by a 14-d washout period.
Subjects performed a 30-s maximal effort cycle ergometer trial prior to and following supplementation. Muscle TCr and PCr were determined prior to and following exercise.
Muscle TCr was significantly increased following creatine supplementation by 20 to 21 mmol/kg dry mass. No significant differences were observed between groups in gains in PCr (creatine 6.4 vs. placebo 2.5 mmol/kg dry mass). No significant differences were observed between groups in peak power, mean power, or decline in power.
Vanderberghe et al. (17)
9 male subjects ingested a placebo, 0.5 g/kg/d of creatine, or 0.5 g/kg/d of creatine with 5 mg/kg/d of caffeine for 6-d.
Prior to and following supplementation, subjects performed three consecutive plantar flexion maximal isometric contractions followed by performing a set of 90, 80 and 50 maximal effort knee extension contractions with a 2-min rest recovery between sets. 31P NMR of the gastrocnemius measured resting and post-isometric contraction ATP and PC concentrations. Dynamic knee extensor torque production was measured using an isokinetic dynamometer.
Creatine supplementation did not significantly affect ATP concentrations. Muscle PCr levels were significantly increased by 4 to 6% in both groups receiving creatine. Muscle torque production was significantly increased by 10-23% in the group ingesting creatine but not in the group ingesting creatine and caffeine.
Vanderberghe et al. (18)
In a double blind and randomized manner, 19 untrained females ingested a placebo or 20 g/d of creatine for 4-d. Subjects then ingested 5 g/d thereafter for 66-d. A subset of 13 subjects then terminated training while maintaining low dose supplementation. Subjects were then evaluated 28-d following cessation of supplementation.
Prior to and following 4-, 35- and 70-d of supplementation, total PCr and the ratio of PCr/ATP were determined using 31P NMR. In addition, strength tests (30 maximal effort arm flexion contractions), training lifting volume , and hydrostatically determined body composition assessments were performed. A subset of 13 subjects were also evaluated at 7-, 28-, and 70-d of cessation of supplementation and detraining.
NMR determined total PCr and the ratio of PCr/ATP were significantly increased by 6% following 4-d of supplementation in the creatine group. These values were maintained during the low dose supplementation phase. Urine volume did not differ between groups however creatine supplementation increased creatine. Creatine supplementation resulted in significantly greater increases in maximal strength (20 to 25%), maximal intermittent exercise performance (10 to 25%), and fat free mass (60%) in comparison to the placebo group. After cessation of training, gains in strength and fat free mass were maintained in the creatine group ingesting 5 g/d of creatine. Muscle PCr levels declined after 28-d of cessation of supplementation. However, gains in fat free mass were maintained in the creatine group.
Casey et al. (19)
9 male subjects ingested 20 g/d of creatine for 5-d.
Prior to and following supplementation, subjects performed two 30-s bouts of cycling. Muscle biopsies were obtained to determine total creatine, ATP, and PCr content.
Creatine supplementation resulted in significant increases in resting PCr in both type I and II fibers. Total creatine content in muscle increased by 23 mmol/kg dry mass. Total work in both exercise bouts increased by 4%. There was 31% less loss in ATP despite producing more work in the creatine group. Changes in resting PCr in type II fibers were positively correlated to changes in PCr during exercise and changes in total work.
Becque et al. (20)
In a double blind and randomized manner, 23 male resistance trained athletes ingested either 20 g/d of creatine for 7-d and 2 g/d of creatine for 35-d or a sucrose placebo.
Subjects performed 1RM biceps curl strength tests and had body composition determined by hydrostatic weighing prior to and following supplementation.
Subjects ingesting creatine observed a significantly greater gain in 1RM strength (11.9 vs 6.8 kg). Body mass (2 kg), and fat free mass (1.6 kg) were significantly increased in the creatine group while no changes were observed in the placebo group.
Birch et al. (21)
In a double blind and randomized manner, 14 male subjects ingested either 20 g/d of creatine or an equivalent amount of a placebo for 5-d.
Subjects performed 3 x 30-s maximal effort isokinetic cycling sprints with 4- min of passive recovery between sprints. Blood samples were obtained prior to and following exercise to determine ammonia and lactate levels.
Peak power output was significantly increased (8%) in the creatine group during sprint 1. Mean power output (6%) and work performed (9%) were significantly increased in sprints 1 and 2 following creatine ingestion. No significant differences were observed in sprint 3. Plasma ammonia levels were decreased following creatine supplementation. No differences were observed between groups in lactate levels.
Earnest et al. (22)
In a double blind and randomized manner, 10 resistance trained male subjects ingested either 20 g/d of creatine or a placebo for 28-d during training.
Prior to and following supplementation, subjects performed 3 x 30-s Wingate cycle ergometer tests with 5-min rest recovery between trials; a 1RM bench press test; a bench press repetition test at 70% 1 RM; and had body composition determined by hydrostatic weighing.
Creatine supplementation resulted in significant increases in work performed in the 3 x 30-s Wingate tests (15, 24, & 23%); an 8% increase in 1 RM bench press in the creatine group; a 43% increase in lifting volume; and a 1.7 kg increase in body mass in which FFM accounted for 1.6 kg of the gain (p=0.054).
Greenhaff et al. (23)
In a double blind and randomized manner, 9 male and 3 female active but not highly trained subjects ingested either 20 g/d of creatine with 4 g/d of glucose or 24 g/d of glucose for 5-d.
Subjects performed 5 sets of 30 maximal knee extension contractions with 60-s rest between sets on an isokinetic dynamometer. Blood samples were obtained to measure plasma ammonia and blood lactate.
Creatine supplementation resulted in a significant increases in total peak torque during bouts 2 and 3 and approached significance in the 4th set. In addition, total peak torque in the last 10 repetitions of set 1 was significantly greater in the creatine group. Plasma ammonia levels were significantly lower following the 4th and 5th set of exercise in the group receiving creatine. No significant differences were observed between groups in blood lactate levels.
Stout et al. (24)
In a double blind and randomized manner, 24 Division II football players ingested either a flavored powder containing 35 g of glucose (G); 5.25 g of creatine with 1 g of glucose in a flavored powder (Cr); or, the G powder containing 5.25 g of creatine (G/Cr). Subjects ingested these supplements four times per day for 5-d and twice a day for 56-d during off-season resistance training.
Prior to and following supplementation, subjects had body composition determined by dual energy x-ray absorptiometry (DEXA) and performed 1 RM bench press, vertical jump, and 100 yd sprints.
In comparison to the placebo group, subjects ingesting G/Cr had significantly greater gains in FFM (2.9 kg), bench press 1RM (16 kg), and vertical jump performance (4.3 cm) while decreasing 100 yd dash time by an additional (-0.29-s). Subjects ingesting creatine observed greater gains in FFM (2.6 kg), bench press 1RM (4.4 kg), and vertical jump performance (3.8 cm) while decreasing 100 yd dash time by an additional (-0.22-s) in comparison to the placebo group but these differences were not statistically significant due to between-subject variability.
Volek et al. (25)
In a double blind and randomized manner, 14 resistance-trained male subjects ingested 25 g/d of creatine or a placebo for 7-d.
Subjects performed 5 sets to failure at their 10 RM max for the bench press with 2-min recovery between sets. The next day, subjects performed 5 sets of 10 repetitions of jump squats at 30% of the subjects 1 RM in the squat. Body composition was assessed using skinfolds and blood lactate was determined prior to and following exercise bouts.
Body mass was significantly increased by 1.1 kg with no significant differences observed in sum of skinfold measurements. Creatine supplementation resulted in a significant increase in the number of repetitions performed in all 5 sets of the bench press and jump squat.
Goldberg et al. (26)
34 Division I-A football and track athletes ingested either 3 g/d of creatine or a placebo for 14-d during training.
Prior to and following supplementation, subjects had body mass, vertical jump, and 40 yd sprint times determined. In addition, subjects performed 1RM bench press, leg sled, and leg extension tests.
Body weight (0.9 kg) and vertical jump performance (2.6%) were significantly increased in the creatine group. No significant differences were observed between groups in 1 RM bench press, 40 yd sprint times, leg sled endurance, or leg extension performance.
Bosco et al. (27)
In a double blind and randomized manner, qualified male sprinters and jumpers ingested either 20 g/d of creatine or a placebo for 5-d.
Subjects performed a 45-s maximal continuous jumping test and an all-out treadmill run to exhaustion at 20 km/h (lasting about 60-s).
Creatine supplementation promoted a 7% improvement in jumping performance during the first 15-s of the jump test and a 5% improvement in jump performance in the second 15-s segment. Run time to exhaustion was increased by 13% in the creatine group.
Almada et al. (28)
In a double blind and randomized manner, 41 NCAA Division I-A football players ingested a glucose powder (G), the G with 3 g/d of calcium HMB, or the G/HMB supplement with 15.75 g/d of creatine for 28-d during resistance/
agility training.
Subjects performed 12 x 6-s cycle ergometer sprints with 30-s rest recovery, lifting volume in bench press, squat, and power clean.
There was some evidence that subjects administered creatine with the GET/HMB supplement observed greater gains in mean work performed during the repetitive sprint performance (p=0.06) and greater gains in and squat (p=0.08) and power clean (p=0.008) lifting volume.
Hamilton-Ward et al. (29)
In a double blind and randomized manner, 20 female racquet players ingested either a placebo or 25 g/d of creatine for 7-d.
Prior to and following supplementation, subjects performed 1 RM internal rotation tests and an elbow flexion test to fatigue.
No significant differences were observed between groups in concentric and eccentric 1 RM internal rotation force or in elbow flexion to fatigue. There was a non-significant 0.7 kg increase in body mass.
Johnson et al. (30)
In a double blind and randomized manner, 18 male and female subjects ingested either a placebo or 20 g/d of creatine for 6-d.
Prior to and following supplementation, subjects performed concentric/eccentric maximal power output knee extension exercises. This was followed by an isotonic muscular fatigue test.
Creatine supplementation resulted in significant increases concentric peak power (6%), eccentric peak power (9%), total concentric work (25%), and total eccentric work (15%).
Kreider et al. (31)
In a double blind and randomized manner, 25 Division I-A football players ingested either a glucose, electrolyte, and taurine placebo or this placebo with 15.75 g/d of creatine for 28-d during resistance/
agility training.
Prior to and following supplementation, subjects: 1.) had body weight, total body water, and body composition determined by DEXA; 2.) donated fasting blood samples; 3.) performed 12 x 6-s maximal effort cycle ergometry sprints with 30-s rest recovery; and, 4) performed a maximal repetition test on the isotonic bench press, squat and power clean.
Clinical blood profiles remained within normal for athletes engaged in intense training. However, subjects ingesting creatine observed greater increases in creatinine, CK, LDH, and ALT levels while the ratio of urea nitrogen/creatinine was decreased. In addition, postivie lipid modifying effects were observed. Gains in body mass (2.4 kg) and fat/bone free mass (2.4 kg) in the creatine group were significantly greater than the placebo group. Sprint performance during the first 5 of 12 x 6-s sprints and overall gains in lifting volume was significantly greater in the creatine group.
Grindstaff et al. (32)
In a double blind and randomized manner, 11 female and 9 male regional and nationally competitive U.S. junior swimmers ingested either 21 g/d of creatine with 4 g/d of maltodextrin or 25 g/d of maltodextrin for 9-d during training.
Prior to and following supplementation, subjects had body mass, total body water, and body composition measurements via skinfolds determined. In addition, subjects performed 3 x 100-m competitive freestyle swims with 60-s rest recovery between trials and 3 x 20-s upper extremity isokinetic arm ergometer tests in the prone position with 60-s rest recovery between sprints.
Body mass was non-significantly increased (0.5 kg) in the creatine group. However, there was some evidence that fat mass (p=0.08) and body composition (p=0.09) was decreased in the creatine group. 100-m swim times were significantly faster in the creatine group in heat 1 (1.1-s). In addition, creatine supplementation significantly decreased swim times in the second 100-m heat by 0.93-s. There was some evidence of improved swim times for all three 100-m sprints (p=0.057). Upper extremity work in the creatine group was significantly greater than placebo responses after 20-s sprint trial (7.8%) but was not significantly greater than placebo responses in sprint 2 (5.3%) or sprint 3 (0.5%).
Prevost et al. (33)
18 subjects ingested a calcium chloride placebo for 5-d days prior to pre-testing. Subjects were then administered in a double blind and randomized manner either the placebo or 18.75 g/d of creatine for 5-d prior to post-testing and 2.25 g of creatine each day during post-testing.
Prior to and following supplementation, subjects cycled to exhaustion using a work rate approximating 150% of VO2 peak under the following conditions: 1.) cycle continuously to exhaustion; 2.) cycle intermittently for 60-s work/120-s rest recovery; 3.) cycle intermittently for 20-s work/40-s rest recovery; or, 4.) cycle intermittently for 10-s /20-s rest recovery.
Creatine supplementation resulted in significant increases in total work for all exercise bouts with the greatest improvement in work performed observed in the 10-s work/20-s rest recovery protocol [Protocol 1(23.5%), Protocol 2 (61%), Protocol 3 (62%), Protocol 4 (100%)].
Ziegenfuss et al. (34)
In a double blind and randomized manner, 33 trained male and female subjects ingested either 0.35 g/kg/d of creatine or a maltodextrin placebo for 3-d or 5-d.
Subjects had muscle thigh volume determined by MRI and intra and extracellular water determined by BIA. In addition, subjects performed 6 x 10-s cycle ergometer sprints to determine anaerobic power. Finally, whole body protein turnover ([15N] glycine) was determined in three subjects to evaluate whether creatine affects protein synthesis/catabolism
Results revealed that total work in the first, and peak power in the last 5 x 10-s sprints were increased in the Cr group. Muscle thigh volume increased by 7% in 5 of 6 subjects. Total body and intracellular water increased by 2-3%. Nitrogen status was increased by either increased protein synthesis or a decreased protein breakdown. There was no gender or training mode effects observed.
Balsom et al. (35)
In a double blind and randomized manner, 18 active to well-trained male subjects ingested either 30 g/d of creatine with 6 g/d glucose or 36 g/d of glucose for 6-d.
Treadmill time to exhaustion lasting 3-4 min and a 6-km outdoor terrain run. Oxygen uptake was determined during treadmill run. Post-exercise heart rate, lactate, and hypoxanthine levels determined.
Subjects observed a significant increase (0.9 kg) in body mass in the creatine group. There was no significant differences between groups in time to treadmill exhaustion (placebo +0.21 min, creatine +0.25 min). Significantly greater increases in lactate occurred in creatine group following treadmill run. There was a significant increase in time to perform the 6-km run presumably due to weight gain.
Dawson et al. (36)
In a double blind and randomized manner, 18 male subjects (Study I) and 11 male subjects (Study II) performed baseline tests and then ingested either 20 g/d of creatine or glucose for 5-d.
Study I. Subjects performed one 10-s cycling sprint trial prior to and one and three days following supplementation. Study II. Subjects performed 6 x 6-s cycle ergometer sprints with 30-s rest recovery between sprints.
Study I: No significant differences between pre- and post-supplementation work performed in the 10-s sprint. Study II: Creatine supplementation resulted in significant increases in total work performed during the 6 x 6-s sprints, work completed in sprint 1 and peak power.
Ferreira et al. (37)
In a double blind and randomized manner, 25 Division I-A football players ingested either a glucose, electrolyte, and taurine placebo or this placebo with 15.75 g/d of creatine for 28-d during resistance/
agility training.
Prior to and following supplementation, subjects: 1) performed 12 x 6-s maximal effort cycle ergometry sprints with 30-s rest recovery; and, 2) performed a maximal repetition test on the isotonic bench press and squat.
Sprint performance during the first 5 of 12 x 6-s sprints, bench press lifting volume, and overall gains in lifting volume were significantly greater in the creatine group.
Harris et al. (38)
In a double blind and randomized manner, 10 trained middle distance male runners ingested either a placebo or 30 g/d of creatine with 5 g/d of glucose for 6-d.
Prior to and following supplementation, subjects performed 4 x 300-m maximal effort runs with 4-min rest recovery. On the next day, subjects performed 4 x 1,000-m runs with 3-min rest recovery.
Creatine supplementation resulted in significant decreases in final 300-m and 1,000-m run performance times. In addition, total time to perform the 4 x 1,000-m runs was significantly improved in the creatine group. Best 300-m and 1,000-m times were significantly reduced by -0.3-s and -2.1-s in the creatine group.
Kirksey et al. (39)
In a double blind and randomized manner, 16 male and 20 female track athletes ingested either 0.3 g/kg/d of creatine or a placebo for 42-d during pre-season conditioning.
Prior to and following supplementation, subjects had body composition measured using hydrodensitometry and skinfolds. In addition, subjects performed static and counter movement vertical jumps and 5 x 30-s Wingate cycle ergometer tests.
Creatine supplementation resulted in significantly greater increases in FFM (4.8 vs. 3.5 kg) and average peak power for the Wingate tests (106 vs. 38 W). No group x time x gender effects were observed.
Leenders et al. (40)
In a double blind and randomized manner, 6 female college swimmers ingested either 20 g/d of creatine or a placebo for 14-d during training.
During training and performance trial sets, subjects performed interval sets of 6 x 50-m swims with 180-s recovery, 10 x 25-m swims with 60-s recovery, and 12 x 100-m swims with 150-s recovery.
No significant differences were observed between groups in 10 x 25-m or 12 x 100-m sprint times. However, swim times to perform the 6 x 50-m set were significantly reduced. In addition, a significant linear trend for increased interval set swim velocity was observed in the creatine group.
Earnest et al. (41)
In a double blind manner, 8 male and 7 female active subjects ingested either 20 g/d of creatine or a placebo for 5-d.
Subjects complete familiarization and baseline trials to establish work rates designed to elicit fatigue in 90-600-s. Subjects then performed three experimental trials after 5-d of supplementation to evaluate the effects of creatine supplementation on time to exhaustion at various work rates.
Subjects ingesting creatine produced significantly greater work due to its effect on extending exercise time primarily at the shorter, higher intensity work rates.
Rossiter et al. (42)
In a double blind manner, 19 competitive rowers ingested either 0.25 g/kg/d of creatine or a placebo for 5-d.
Total creatine uptake was estimated by monitoring urine creatine output. Subjects performed a 1,000-m rowing performance trial to evaluate the ergogenic effects of creatine on rowing performance.
Calculated total creatine uptake over the 5-d period averaged 35 g with an estimated muscle uptake of 38 mmol/kg dry mass. No change was observed in performance time for the placebo group (214 to 214-s). However, performance time was significantly decreased in the creatine group (211 to 208.7-s). The increase in creatine uptake was non-significantly correlated to performance times (r=0.43, p=0.09).
Earnest et al. (43)
In a double blind and randomized manner, 11 trained male subjects ingested either 20 g/d of creatine with 4 g/d of glucose for 4-d followed by ingesting 10 g/d of creatine for 6-d or a placebo.
Prior to and following supplementation, subjects performed two treadmill runs to exhaustion at 214 m/min with a grade determined to elicit fatigue within 90-s. The treadmill runs were separated by an 8-min rest recovery. Blood lactate levels were determined prior to and following exercise.
No significant differences were observed between groups in changes in body mass. Creatine supplementation significantly improved total treadmill time to exhaustion (placebo 166 to 163.8; creatine 176.5 to 182.2-s). The greatest improvement was observed in the second run to exhaustion. Post-exercise blood lactate levels were significantly greater following exercise in the creatine group.
Nelson et al. (44)
19 male and 9 female trained runners performed pre-testing and then ingested 20 g/d of creatine for 7- to 8-d.
Prior to and following supplementation, subjects performed an incremental maximal exercise test to determine maximal VO2and ventilatory anaerobic threshold (VANT). In addition, pre- and post-exercise blood lactate and ammonia concentrations were determined.
No significant differences were observed in peak VO2. However, creatine supplementation resulted in a significant increase in VANT (67% to 74%). In addition, there was a significant decrease in blood lactate and ammonia.
Jacobs et al. (45)
In a double blind and randomized manner, 26 male and female subjects ingested either 20 g/d of creatine or a placebo for 5-d.
Subjects exercised to exhaustion at a work rate equivalent to 125% of VO2max prior to, following 5-d of supplementation, and 7-d following cessation of supplementation. Time to exhaustion and maximal accumulated oxygen deficit (MAOD) was determined during each trial.
Creatine supplementation significantly increased time to exhaustion at 5-d following supplementation (130 to 141-s or 8%) and remained increased following 7-d of cessation of supplementation (139-s or 7%). In addition, MOAD was significantly increased by 9% after 5-d and remained elevated by 7% after 7-d of cessation of supplementation.
Myburgh et al. (46)
In a double blind and randomized manner, 13 trained cyclists ingested either 20 g/d of creatine or a placebo for 7-d and then maintenance doses (2 g/d) of creatine or the placebo during 7-d of interval sprint training.
Muscle biopsies and blood samples were obtained prior to and following 7-d of supplementation and 1-d after 7-d of sprint training (10 x 10-s sprints with 140-s rest recovery for 7-d). In addition, subjects performed a 30-s cycle ergometry Wingate anaerobic power test and a 1-h performance time trial.
Muscle creatine content was significantly increased by 21% in the creatine group (121 to 147 mmol/kg dry mass). The increase in total creatine content was significantly correlated to the percentage of type IIb muscle fiber. No significant differences were observed between groups in resting and post-sprint training ATP levels, blood lactate, ammonia, or hypoxanthine levels. In addition, no differences were observed between groups in anaerobic power during the 30-s Wingate test or in 1-h time trial performance.
Balsom et al. (47)
In a double blind and randomized manner, 16 active but not highly trained male subjects ingested either 25 g/d of creatine with 5 g/d of glucose or 30 g/d of glucose for 5-d.
10 x 6-s cycle ergometer sprints with 30-s rest recovery at 130 and 140 rev/min. Blood samples were taken to determine lactate and hypoxanthine levels. Post-exercise oxygen uptake was also measured.
Subjects ingesting creatine observed a significant increase in body mass (1.1 kg). No differences were observed between groups at the 130 rev/min intensity. Sprint performance during the 4 to 6-s segment in the creatine group was significantly greater in the creatine group in the latter sprints. Blood lactate and hypoxanthine levels were lower in the creatine group despite performing more work. No significant differences in post-exercise oxygen uptake.
Thompson et al. (48)
10 female swimmers ingested either 2 g/d of creatine or a placebo for 42-d during training.
Resting and exercise (10 to 15-min of submaximal plantar flexion contractions) ATP and PC concentrations were determined using 31P MRS.
No significant differences were observed between groups in resting, exercise, or post-exercise bioenergetics.
Odland et al. (49)
In a double blind, crossover manner, 9 untrained male subjects ingested 20 g/d of creatine or a placebo for 3-d. Following a 14-d washout period, subjects repeated the experiment following ingestion of the alternate supplement.
Prior to and following each supplementation period, subjects performed a 30-s Wingate cycle ergometer anaerobic power test.
No significant differences were observed between placebo and creatine supplemented trials.
Burke et al. (50)
In a double blind and randomized manner, 18 male and 14 female Australian National Team swimmers ingested 20 g/d of creatine or a sucrose placebo for 5-d.
Subjects performed single effort swim performance trials at 25-, 50-, and 100-m distances with a 10-min active recovery performed between sprint tests and a 10-s sprint on a cycle ergometer prior to and following supplementation.
No significant differences between groups in swim performance or 10-s cycling sprint performance.
Cooke et al. (51)
In a double blind and randomized manner, 12 untrained male subjects ingested either 20 g/d of creatine with 4 g/d of glucose or 24 g/d of glucose for 5-d.
Subjects performed 2 x 15-s cycle ergometry sprint trials separated by a 20-min rest recovery between sprints.
No significant differences between groups in cycling power or work performed.
Mujika et al. (52)
In a double blind and randomized manner, 9 male and 11 female swimmers ingested either 20 g/d of creatine or a placebo for 5-d.
Prior to and following supplementation, subjects performed 25-m, 50-m, 100-m sprint trials with 20- to 25-min rest recovery between sprints. Post-exercise blood samples were obtained to determine blood lactate and ammonia concentrations.
Body mass significantly increased by 0.7 kg in the creatine group. No significant differences were observed between groups in performance times or lactate concentrations. Post-exercise ammonia levels were significantly lower at the 50- and 100-m distances in the creatine group.
Redondo et al. (53)
In a double blind and randomized manner, 14 female college field hockey players and 8 male baseball players ingested either 25 g/d of creatine or a placebo for 7-d.
Subjects performed three 60-m sprints separated by 5-min resting recovery. Biomechanical analysis of running velocity and stride length were determined at 20- to 30-m, 40- to 50-m, and 50- to 60-m zones.
Body mass non-significantly decreased by -0.8 kg in the creatine group. No significant differences were observed between groups in running velocities or stride length.
Barnett et al. (54)
17 active male subjects were administered 40 g/d of glucose for 4-d. Subjects were then matched based on sprint performance and were then administered 0.28 g/kg/d of creatine for 4-d.
Subjects performed 7 x 10-s cycle ergometer sprints with 30-s rest recovery for sprints 1 through 5. Subjects then rested for 5-min and completed sprint 6 and 7 with a 30-s rest recovery between sprints. Blood samples were obtained prior to, after the 5thsprint, before the 6thsprint, and following sprint 7. Post-exercise oxygen uptake was measured for 5-min following sprint 7.
No significant differences were found in multiple sprint performance power output, plasma lactate, blood pH, or post-exercise oxygen uptake.
Terrilion et al. (55)
In a double blind and randomized manner, 12 trained male runners ingested either 20 g/d of creatine or a placebo for 5-d.
Prior to and following supplementation, body mass and total body water were determined. In addition, subjects performed two 700-m outdoor runs with 60-min recovery between trials. Blood samples were collected to evaluate changes in blood lactate.
No significant differences were observed between groups in changes in body mass (placebo -0.4; creatine 0.6 kg) or in total body water. No significant differences were observed between groups in changes in performance times for each trial (placebo 0.2, -0.4-s, creatine 0.5, -1.9-s) or in blood lactate concentrations.
Godly et al. (56)
In a double blind and randomized manner, 13 male and 3 female well-trained cyclists ingested either 24 g/d of creatine or a placebo for 5-d.
Prior to and following supplementation, subjects performed a 25-km cycling time trial on their own bike attached to a computerized simulator interspersed with 15-s all out sprints at 4-km intervals.
No significant differences were observed between groups in changes in total body mass. Performance times in the creatine group decreased from 41.36- to 40.34-min compared to 41.97- to 41.75 -min in the placebo group. However, this difference was not statistically significant.
Stroud et al. (57)
8 males subjects performed pre-testing and then consumed 20 g/d of creatine for 5-d.
Prior to and following supplementation, subjects performed a continuous incremental exercise test running at 10 km/h at workloads eliciting 50% to 90% of VO2max for 6-min each. Respiratory gases and blood lactate were determined at each workload and at 5-min intervals during recovery.
No significant differences were observed in respiratory exchange ratio or blood lactate at each workload.
Kreider et al. (59)
In a double blind and randomized manner, 41 Division I-A football players ingested either a glucose placebo (G), the G with 3 g/d of calcium HMB (G/HMB), or the G/HMB supplement with 15.75 g/d of creatine (G/HMB/Cr) for 28-d during resistance/
agility training.
Prior to and following supplementation, subjects had total body mass, total body water, and body composition determined using DEXA.
Subjects ingesting G/HMB/Cr observed significantly greater increases in body mass (1.2 kg) and FFM (1.3 kg) with no changes in total body water in comparison to subjects ingesting G and the G/HMB supplement.
Kreider et al. (63)
In a double blind and randomized manner, 52 Division I-A football players ingested near isoenergetic amounts of a maltodextrin placebo, Phosphagain® containing 20 g/d of creatine (P-I), or Phosphagain II® containing 25 g/d of creatine for 35-d during resistance/ agility training.
Prior to and following 35-d of supplementation, subjects had body composition determined using DEXA. In addition, subjects performed 1 RM tests at 0.25, 0.99, and 1.54 m/s as well as 5 sets of 15 maximal effort contractions at 0.25 m/s with 60-s rest recovery between sets on an isokinetic bench press.
Subjects ingesting P-I (2.4 kg) and P-II (3.5 kg) observed significantly greater gains in FFM in comparison to the placebo group (1 kg). In addition, subjects ingesting P-I and P-II observed significantly greater gains in 1RM strength at 0.99 m/s. No significant differences were observed among groups in remaining 1 RM velocities or in gains in mean peak force, average force, or total work performed during the 5 sets of 15 maximal effort contractions at 0.25 m/s.
Kreider et al. (64)
In a double blind and randomized manner, 28 resistance- trained male subjects ingested a maltodextrin placebo, a higher calorie carbohydrate/protein weight gain powder (Gainers Fuel 1000®), or Phosphagain® containing 20 g/d of creatine for 28-d during training.
Subjects had total body mass, total body water, and body composition determined using DEXA on days 0, 7, 14 and 28 of supplementation.
Subjects ingesting Phosphagain® observed significantly greater gains in body mass and FFM (1.1 to 1.3 kg) than subjects ingesting the placebo and higher calorie weight gain powder. The greatest gains occurred in the first 14-d of supplementation.
Kreider et al. (65)
In a double blind and randomized manner, 24 untrained and 26 endurance trained males and females ingested either a glucose placebo (G), 16.5 g/d of creatine, or the G placebo with 15.75 g/d of creatine for 14-d.
Prior to and following supplementation, subjects had total body mass, total body water, and body composition determined via skinfolds.
In both untrained and trained subjects, creatine supplementation resulted in significantly greater increases in body mass and FFM (0.9 kg). No differences were observed between groups ingesting creatine alone or creatine with glucose. There was some evidence that untrained and trained men observed greater gains in FFM in response to creatine supplementation (1.4 kg) than women (0.3 kg).
Sipilä et al. (67)
2 female and 5 male gyrate atrophy patients performed pre-tests and then the were administered 1.5 g/d of creatine for 1 year.
Prior to and at 3-month intervals during the supplementation period, subjects had serum and urinary amino acids, creatine, creatinine, and muscle and liver enzyme levels determined. In addition, muscle biopsies were obtained to determine muscle fiber types and diameter, body mass was measured, and ophthalmologic examinations were performed.
Creatine supplementation resulted in a 10% increase in total body mass. Muscle biopsy analysis revealed that type II fiber diameter increased by 34% with no effect on type I fiber. There were occasional increases in muscle and liver enzyme efflux and serum and urinary creatine and creatinine levels. However, these parameters remained within normal limits. No effects were observed in ophthalmologic exam results. No side effects were reported.
Almada et al. (68)
In a double blind and randomized manner, 34 untrained men and women (mean of 51 years) subjects ingested either 20 g/d of creatine for 5-d and 10 g/d of creatine for 51-d or a glucose placebo.
Muscle and liver enzymes changes were monitored at 0, 4, and 8 weeks of supplementation and following 4 weeks of cessation.
There was no significant differences in AST, ALT, ALP, GGT, LDH, or CK between groups. Males ingesting creatine had greater increase in CK levels than females taking creatine (119 to 181 IU)
Earnest et al. (69)
In a double blind and randomized manner, 18 male and 16 female middle-aged subjects (32-70 yrs) ingested either a placebo or 20 g/d of creatine with 4 g/d of glucose for 5-d and 10 g/d of creatine with 2 g/d of glucose for 51-d.
Subjects had plasma lipid, lipoprotein, glucose, urea nitrogen, and creatinine profiles determined at 0, 28, and 56-d of supplementation as well as 28-d following cessation of supplementation.
No significant differences were observed between groups in body mass. Creatine supplementation resulted in significant decreases in total cholesterol (-5 and -6% at day 28 and 56-d, respectively), triglycerides (-23 and -22% at day 28 and 56-d, respectively). A similar response was observed for VLDL. No significant differences were observed between groups in glucose, creatinine or urea nitrogen. However, women ingesting creatine observed a modest increase in urea nitrogen.
Gordon et al. (75)
In a double blind and randomized manner, 17 heart failure patients with less than a 40% ejection fraction ingested either 20 g/d of creatine or a placebo for 10-d.
Prior to and following supplementation, subjects had ejection fraction determined using radionuclide angiography. In addition, subjects performed symptom-limited 1-legged knee extension strength tests and a cycle ergometry performance test. Muscle biopsies were obtained to evaluate TCr and PCr concentrations.
Creatine supplementation significantly increased muscle TCr by 17% and PCr by 12%. Increments were seen only in patients with TCr less than 140 mmol/kg dry mass. Creatine supplementation did not affect resting or post-exercise ejection fraction. Creatine supplementation significantly increased one-legged knee extensor performance (21%), cycle ergometer performance (10%), and peak torque (5%). Gains in peak torque and knee extensor performance were correlated to muscle PCr content.
Poortmans et al. (76)
In a double blind and randomized manner, 5 subjects ingest either a placebo or 20 g/d of creatine for 5-d.
Subjects had blood and urine samples determined to creatine, creatinine, total protein, albumin, and urine output.
Creatine supplementation increased arterial (3.7 fold) and urinary excretion of creatine. Blood and urine creatinine levels were not affected by creatine supplementation. The glomular filtration rate (creatinine clearance) and total protein and albumin excretion rates remained within normal limits.