Creatine Creatine ingestion favorably affects performance and muscle metabolism during maximal exercise in humans
Casey A, Constantin-Teodosiu D, Howell S, Hultman E, Greenhaff PL. Am J Physiol 1996;271(1 Pt 1):E31-7.
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 approximately 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 +/- 12.2% less after Cr ingestion, despite the increase in work production. Resting phosphocreatine (PCr) 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.
Effects of oral creatine loading on single and repeated maximal short sprints.
Dawson B, Cutler M, Moody A, Lawrence S, Goodman C, Randall N. Aust J Sci Med Sport 1995;27(3):56-61.
This investigation determined whether oral creatine (Cr) loading could enhance single and repeated short sprint performance. A 1 x 10 s cycle sprint (Study One) and 6 x 6 s (departing every 30 s) repeated cycle sprints (Study two) were the performance tests used. Separate groups of subjects, randomly assigned to either a Cr or placebo (P) group, were used in each study in a double blind design. After performing a familiarization and two baseline tests subjects loaded with 5g of Cr or P four times per day for five days before repeating the tests one and three days post-loading. In Study One (n = 9 in each group), work completed (kJ) at 2, 4, 6, 8 and 10 s and peak power (W) were greater than baseline values in each of the post-loading trials in both the Cr and P groups. There were no between group performance differences. In Study Two (n = 11 in each group) after loading, the Cr group recorded significantly greater scores than the P group in total work (kJ) completed over the 6 sprints, work completed in sprint 1, and peak power (W). Post-exercise blood lactate and pH responses were not different between the Cr and P groups after loading in either study. Although Study One results are equivocal, Study Two results suggest that Cr supplementation can enhance both single (if sprint 1 results are considered in isolation) and repeated short sprint performance.
Creatine supplementation in chronic heart failure increases skeletal muscle creatine phosphate and muscle performance
Gordon A, Hultman E, Kaijser L, Kristjansson S, Rolf CJ, Nyquist O, Sylven C. Cardiovasc Res 1995;30(3):413-8.
BACKGROUND: Cardiac creatine levels are depressed in chronic heart failure. Oral supplementation of creatine to healthy volunteers has been shown to increase physical performance.
AIM: To evaluate the effects of creatine supplementation on ejection fraction, symptom- limited physical endurance and skeletal muscle strength in patients with chronic heart failure.
METHODS: With a double-blind, placebo- controlled design 17 patients (age 43-70 years, ejection fraction < 40) were supplemented with creatine 20 g daily for 10 days. Before and on the last day of supplementation ejection fraction was determined by radionuclide angiography as was symptom-limited 1-legged knee extensor and 2-legged exercise performance on the cycle ergometer. Muscle strength as unilateral concentric knee extensor performance (peak torque, Nm at 180 degrees/s) was also evaluated. Skeletal muscle biopsies were taken for the determination of energy-rich phosphagens.
RESULTS: Ejection fraction at rest and at work did not change. Performance before creatine supplementation did not differ between placebo and creatine groups. While no change was seen in the placebo group compared to baseline, creatine supplementation increased skeletal muscle total creatine and creatine phosphate by 17 +/- 4% (P < 0.05) and 12 +/- 4% (P < 0.05), respectively. Increments were seen only in patients with < 140 mmol total creatine/kg d.w. (P < 0.05). One-legged performance (21%, P < 0.05), 2-legged performance (10%, P < 0.05), and peak torque, Nm (5%, P < 0.05) increased. Both peak torque and 1-legged performance increased linearly with increased skeletal muscle phosphocreatine (P < 0.05). The increments in 1-legged, 2-legged and peak torque were significant compared to the placebo group, (P < 0.05). CONCLUSIONS: One week of creatine supplementation to patients with chronic heart failure did not increase ejection fraction but increased skeletal muscle energy-rich phosphagens and performance as regards both strength and endurance. This new therapeutic approach merits further attention.
Carbohydrate ingestion augments skeletal muscle creatine accumulation during creatine supplementation in humans.
Green AL, Hultman E, Macdonald IA, Sewell DA, Greenhaff PL. Am J Physiol 1996;271(5 Pt 1):E821-6.
This study investigated the effect of carbohydrate (CHO) ingestion on skeletal muscle creatine (Cr) accumulation during Cr supplementation in humans. Muscle biopsy, urine, and plasma samples were obtained from 24 males before and after ingesting 5 g Cr in solution (group A) or 5 g Cr followed, 30 min later, by 93 g simple CHO in solution (group B) four times each day for 5 days. Supplementation resulted in an increase in muscle phosphocreatine (PCr), Cr, and total creatine (TCr; sum of PCr and Cr) concentration in groups A and B, but the increase in TCr in group B was 60% greater than in group A (P < 0.01). There was also a corresponding decrease in urinary Cr excretion in group B (P < 0.001). Creatine supplementation had no effect on serum insulin concentration, but Cr and CHO ingestion dramatically elevated insulin concentration (P < 0.001). These findings demonstrate that CHO ingestion substantially augments muscle Cr accumulation during Cr feeding in humans, which appears to be insulin mediated.
Creatine and its application as an ergogenic aid.
Greenhaff PL. Int J Sport Nutr 1995;5 Suppl:S100-10:S100-10.
Phosphocreatine (PCr) availability is likely to limit performance in brief, high-power exercise because the depletion of PCr results in an inability to maintain adenosine triphosphate (ATP) resynthesis at the rate required. It is now known that the daily ingestion of four 5-g doses of creatine for 5 days will significantly increase intramuscular creatine and PCr concentrations prior to exercise and will facilitate PCr resynthesis during recovery from exercise, particularly in those individuals with relatively low creatine concentrations prior to feeding. As a consequence of creatine ingestion, work output during repeated bouts of high-power exercise has been increased under a variety of experimental conditions. The reduced accumulation of ammonia and hypoxanthine in plasma and the attenuation of muscle ATP degradation after creatine feeding suggest that the ergogenic effect of creatine is achieved by better maintaining ATP turnover during contraction.
Effect of oral creatine supplementation on skeletal muscle phosphocreatine resynthesis
Greenhaff PL, Bodin K, Soderlund K, Hultman E. Am J Physiol 1994;266 (5 Pt 1):E725-30.
Biopsy samples were obtained from the vastus lateralis muscle of eight subjects after 0, 20, 60, and 120 s of recovery from intense electrically evoked isometric contraction. Later (10 days), the same procedures were performed using the other leg, but subjects ingested 20 g creatine (Cr)/day for the preceding 5 days. Muscle ATP, phosphocreatine (PCr), free Cr, and lactate concentrations were measured, and total Cr was calculated as the sum of PCr and free Cr concentrations. In five of the eight subjects, Cr ingestion substantially increased muscle total Cr concentration (mean 29 +/- 3 mmol/kg dry matter, 25 +/- 3%; range 19-35 mmol/kg dry matter, 15-32%) and PCr resynthesis during recovery (mean 19 +/- 4 mmol/kg dry matter, 35 +/- 6%; range 11-28 mmol/kg dry matter, 23-53%). In the remaining three subjects, Cr ingestion had little effect on muscle total Cr concentration, producing increases of 8-9 mmol/kg dry matter (5-7%), and did not increase PCr resynthesis. The data suggest that a dietary-induced increase in muscle total Cr concentration can increase PCr resynthesis during the 2nd min of recovery from intense contraction.
Influence of oral creatine supplementation of muscle torque during repeated bouts of maximal voluntary exercise in man.
Greenhaff PL, Casey A, Short AH, Harris R, Soderlund K, Hultman E. Clin Sci (Colch) 1993;84(5):565-71.
1. The present experiment was undertaken to investigate the influence of oral creatine supplementation, shown previously to increase the total creatine content of human skeletal muscle (Harris RC, Soderlund K, Hultman E. Clin Sci 1992; 83: 367-74), on skeletal muscle isokinetic torque and the accumulation of plasma ammonia and blood lactate during five bouts of maximal exercise. 2. Twelve subjects undertook five bouts of 30 maximal voluntary isokinetic contractions, interspersed with 1 min recovery periods, before and after 5 days of placebo (4 x 6 g of glucose/day, n = 6) or creatine (4 x 5 g of creatine plus 1 g of glucose/day, n = 6) oral supplementation. Muscle torque production and plasma ammonia and blood lactate accumulation were measured during and after exercise on each treatment. 3. No difference was seen when comparing muscle peak torque production during exercise before and after placebo ingestion. After creatine ingestion, muscle peak torque production was greater in all subjects during the final 10 contractions of exercise bout 1 (P < 0.05), throughout the whole of exercise bouts 2 (P < 0.01), 3 (P < 0.05) and 4 (P = 0.057) and during contractions 11- 20 of the final exercise bout (P < 0.05), when compared with the corresponding measurements made before creatine ingestion. Plasma ammonia accumulation was lower during and after exercise after creatine ingestion. No differences were found when comparing blood lactate levels.
Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation.
Harris RC, Soderlund K, Hultman E. Clin Sci (Colch) 1992;83(3):367-74.
1. The present study was undertaken to test whether creatine given as a supplement to normal subjects was absorbed, and if continued resulted in an increase in the total creatine pool in muscle. An additional effect of exercise upon uptake into muscle was also investigated. 2. Low doses (1g of creatine monohydrate or less in water) produced only a modest rise in the plasma creatine concentration, whereas 5g resulted in a mean peak after 1h of 795 (SD 104) mumol/l in three subjects weighing 76-87 kg. Repeated dosing with 5g every 2h sustained the plasma concentration at around 1000 mumol/l. A single 5g dose corresponds to the creatine content of 1.1 kg of fresh, uncooked steak. 3. Supplementation with 5g of creatine monohydrate, four or six times a day for 2 or more days resulted in a significant increase in the total creatine content of the quadriceps femoris muscle measured in 17 subjects. This was greatest in subjects with a low initial total creatine content and the effect was to raise the content in these subjects closer to the upper limit of the normal range. In some the increase was as much as 50%. 4. Uptake into muscle was greatest during the first 2 days of supplementation accounting for 32% of the dose administered in three subjects receiving 6 x 5g of creatine monohydrate/day. In these subjects renal excretion was 40, 61 and 68% of the creatine dose over the first 3 days. Approximately 20% or more of the creatine taken up was measured as phosphocreatine. No changes were apparent in the muscle ATP content.
Creatine ingestion increases anaerobic capacity and maximum accumulated oxygen deficit.
Jacobs I, Bleue S, Goodman J. Can J Appl Physiol 1997;22(3):231-43.
The purpose of this study was to test the hypothesis that ingestion of creatine monohydrate increases anaerobic exercise capacity, as reflected by the maximal accumulated oxygen deficit (MAOD). Subjects were assigned, double-blind, to placebo (PL, n = 12) or creatine (CR, n = 14) groups and ingested 5-g doses 4 times daily of artificial sweetener or artificially sweetened creatine monohydrate, respectively, for 5 days. On a separate day subjects exercised to exhaustion at 125% VO2max. After two familiarization trials, MAOD was again determined before treatment, after 5 days of PL or CR treatment, and 7 days later. MAOD increased after CR treatment from 4.04 +/- 0.31 to 4.41 +/-0.34 L (p < .001) and remained elevated for another 7 days (4.31 +/- 0.33, p < .001). Time to exhaustion also increased in CR from 130 +/- 7 to 141 +/- 7 s (p < .01) and remained increased for another 7 days (139 +/- 8 s, p < .01). These data demonstrate that ingesting creatine monohydrate for 5 days increases the MAOD, and is likely to have an ergogenic effect on supramaximal exercise performance that persists for at least a week after treatment.
Effect of creatine on aerobic and anaerobic metabolism in skeletal muscle in swimmers.
Thompson CH, Kemp GJ, Sanderson AL, Dixon RM, Styles P, Taylor DJ, Radda GK. Br J Sports Med 1996;30(3):222-5.
OBJECTIVE: To examine the effect of a relatively low dose of creatine on skeletal muscle metabolism and oxygen supply in a group of training athletes.
METHODS: 31P magnetic resonance and near-infrared spectroscopy were used to study calf muscle metabolism in a group of 10 female members of a university swimming team. Studies were performed before and after a six week period of training during which they took either 2 g creatine daily or placebo. Calf muscle metabolism and creatine/choline ratios were studied in resting muscle, during plantar flexion exercise (10-15 min), and during recovery from exercise.
RESULTS: There was no effect of creatine on metabolite ratios at rest or on metabolism during exercise and recovery from exercise. Muscle oxygen supply and exercise performance were not improved by creatine if compared to placebo treated subjects.
CONCLUSIONS: Oral creatine supplementation at 2 g daily has no effect on muscle creatine concentration, muscle oxygen supply or muscle aerobic or anaerobic metabolism during endurance exercise .