Supplement research

Creatine

What is Creatine?

Creatine is a nitrogen-containing compound derived from amino acids and is stored primarily in the muscles. Creatine can be made in the body (1-2g/day) in the liver, kidneys and pancreas. Creatine can also be obtained in the diet, mostly from meat, fish and eggs (1-2g/day). 

Proposed Benefits of Creatine

Creatine is used to increase muscle size and strength and to improve high-intensity exercise performance.

Mechanism of Action of Creatine

About 60% of creatine within the muscle is stored as creatine phosphate. Creatine phosphate provides a brief but rapid source of phosphate for the resynthesis of ATP and therefore is an important fuel source in maximal sprints of 5-10 seconds. ATP provides energy for muscular contraction.
Other functions of creatine involve buffering ATP and ADP content of the muscle, restoring ATP levels after exercise, buffering acid levels in the muscle during exercise. Some research suggests that creatine may stabilise cell membranes. Other research suggests that creatine may directly increase protein synthesis.

Research on Creatine

It appears that about 70% of individuals respond to creatine supplementation. It is presumed that the remainder of individuals may already have maximised muscle creatine stores.
In general creatine supplementation results in an average increase of 15-20% in total creatine content within the muscle (1-3).

High Intensity performance

Many studies have shown ergogenic effect with creatine supplementation during short-term high intensity exercise (4-11). This appears to be due to increased ATP availability and muscle hypertrophy (increased size). There also seems to be an ergogenic effect during high intensity intermittent exercise (5,12-14) and mid-term high intensity exercise (5,15,16).
Several studies have shown no beneficial effect of creatine supplementation on performance (17-20). This may be because the protocols used in these studies did not increase muscle creatine content in excess of 20mmol/kg dm. It has been suggested that this increment is required to exert an ergogenic effect on muscle power output (1).

A recent meta-analysis (a study that combines the results of many studies and statistically analyses them) on the effects of dietary supplements on lean mass and strength gains showed that creatine significantly increased net lean muscle gains and increased muscle strength (21). Eighteen studies were included in this meta-analysis with an average duration of 7.5 weeks. The average loading dose was 19.5g/day for 5 days with an average maintenance dose of 6.7g/day. Creatine supplementation resulted in a net gain in lean mass of 0.36% per week and a net strength gain of1.09% per week.

Endurance performance

Research suggests that for athletes taking part in endurance exercise, any benefits of creatine are likely to be outweighed by creatine-induced body mass gains which will negatively effect endurance performance, especially when weight-bearing (6).

Rating of Efficacy for Creatine

The research on the whole indicates a performance benefit for those involved in short-term high intensity exercise. Creatine appears to be effective at increasing muscle strength and size when combined with a resistance training programme.

9/10 for high intensity short-term exercise

References

1.  Casey A., Constantin-Teodosiu D. and Howell. Creatine ingestion favourably affects performance and muscle metabolism during maximal exercise in humans. Am J Physiol. 271:E31-E37, 1996.
2.  Harris R.C., S?lund K. and Hultman E. Elevation of creatine in resting and exercise muscle of normal subjects by creatine supplementation. Clin Sci. 83:367-374, 1992.
3.  Hultman E., S?lund K. and Timmons J.A. Mucle creatine loading in men. J Appl Physiol. 81:232-237, 1996.
4.  Becque M.D., Lochmann J.D. and Melrose D.R. Effects of oral creatine supplementation on muscular strength and body composition. Med Sci Sports Exerc. 32:654-658, 2000.
5.  Bosco C., Tihanyi J. and Pucspk J. Effect of oral creatine supplementation on jumping and running performance. Int J Sports med. 18:369-372, 1997.
6.  Izquierdo M., Ib?z J. and Gonz?z-Badillo J.J. Effects of creatine supplementation on muscle power, endurance, and sprint performance. Med Sci Sports Exerc. 34:332-343, 2002.
7.  Jowko E., Ostszewski P. and Jank M. Creatine and B-hydroxy-B-methylbutyrate (HMB) additively increase lean body mass and muscle strength during a weight-training program. Nutrition. 17:558-566, 2001.
8.  Kreider R.B., Ferreira M. and Wilson M. Effects of creatine supplementation on body composition, strength, and sprint performance. Med Sci Sports Exerc. 30:73-82, 1998.
9.  Stout J., Eckerson J. and Ebersole K. Effect of creatine loading on neuromuscular fatigue threshold. J Appl Physiol. 88:109-112, 2000.
10.  Tarnopolsky M.A. and MacLennan D.P. Creatine monohydrate supplementation enhances high-intensity exercise performance in males and females. In J Sport Nut. 10:452-463, 2000.
11.  Volek J.S., Duncan N.D. and Mazzetti S.A. Performance and muscle fibre adaptations to creatine supplementation and heavy resistance training. Med Sci Sports Exerc. 31:1147-1156, 1999.
12.  Kamber M., Koster M. and Kreis R. Creatine supplementation, Part I: performance, clinical chemistry, and muscle volume. Med Sci Sports Exerc. 31:1763-1769, 1999.
13.  Shomrat A., Weinstein Y. and Katz A. Effect of creatine feeding on maximal exercise performance in vegetarians. Eur J Appl Physiol. 82:321-325, 2000.
14.  Skare O.C., Skadberg ? and Wisnes A.R. Creatine supplementation improves sprint performance in male sprinters. Scand J Med Sci Sports. 11:96-102, 2001.
15.  Maganaris C.N. and Maughan R.J. Creatine supplementation enhances maximum voluntary isometric force and endurance capacity in resistance trained men. Acta Physiol Scand. 163:279-287, 1998.
16.  McNaughton L.R., Dlaton B. and Tarr J. The effects of creatine supplementation on high-intensity performance in elite performers. Eur J Appl Physiol. 78:236-240, 1998.
17.  Burke L.M., Pyne D.B. and Telford R.D. Effect of oral creatine supplementation on single-effort sprint performance in elite swimmers. Int J Sport Nutr. 6:222-233, 1996.
18.  Cooke W.H., Grandjean P.W. and Barnes W.S. Effect of oral creatine supplementation on power output and fatigue during bicycle ergometry. J Appl Physiol. 78:670-673, 1995.
19.  Redondo D.R., Dowling E.A. and Graham B.L. The effect of oral creatine monohydrate supplementation on running velocity. Int J Sport Nutr. 6:213-221, 1996.
20.  Snow R.J., McKenna M.J. and Selig S.E. Effects of creatine supplementation on sprint performance and muscle metabolism. J Appl Physiol. 84:1667-1673, 1998.
21.  Nissen S.L. and Sharp R.L. Effect of dietary supplements on lean mass and strength gains with resistance exercise: a meta-analysis. J Appl Physiol. 94:651-659, 2002.

Supplement research

Creatine

What is Creatine?

Creatine is a nitrogen-containing compound derived from amino acids and is stored primarily in the muscles. Creatine can be made in the body (1-2g/day) in the liver, kidneys and pancreas. Creatine can also be obtained in the diet, mostly from meat, fish and eggs (1-2g/day). 

Proposed Benefits of Creatine

Creatine is used to increase muscle size and strength and to improve high-intensity exercise performance.

Mechanism of Action of Creatine

About 60% of creatine within the muscle is stored as creatine phosphate. Creatine phosphate provides a brief but rapid source of phosphate for the resynthesis of ATP and therefore is an important fuel source in maximal sprints of 5-10 seconds. ATP provides energy for muscular contraction.
Other functions of creatine involve buffering ATP and ADP content of the muscle, restoring ATP levels after exercise, buffering acid levels in the muscle during exercise. Some research suggests that creatine may stabilise cell membranes. Other research suggests that creatine may directly increase protein synthesis.

Research on Creatine

It appears that about 70% of individuals respond to creatine supplementation. It is presumed that the remainder of individuals may already have maximised muscle creatine stores.
In general creatine supplementation results in an average increase of 15-20% in total creatine content within the muscle (1-3).

High Intensity performance

Many studies have shown ergogenic effect with creatine supplementation during short-term high intensity exercise (4-11). This appears to be due to increased ATP availability and muscle hypertrophy (increased size). There also seems to be an ergogenic effect during high intensity intermittent exercise (5,12-14) and mid-term high intensity exercise (5,15,16).
Several studies have shown no beneficial effect of creatine supplementation on performance (17-20). This may be because the protocols used in these studies did not increase muscle creatine content in excess of 20mmol/kg dm. It has been suggested that this increment is required to exert an ergogenic effect on muscle power output (1).

A recent meta-analysis (a study that combines the results of many studies and statistically analyses them) on the effects of dietary supplements on lean mass and strength gains showed that creatine significantly increased net lean muscle gains and increased muscle strength (21). Eighteen studies were included in this meta-analysis with an average duration of 7.5 weeks. The average loading dose was 19.5g/day for 5 days with an average maintenance dose of 6.7g/day. Creatine supplementation resulted in a net gain in lean mass of 0.36% per week and a net strength gain of1.09% per week.

Endurance performance

Research suggests that for athletes taking part in endurance exercise, any benefits of creatine are likely to be outweighed by creatine-induced body mass gains which will negatively effect endurance performance, especially when weight-bearing (6).

Rating of Efficacy for Creatine

The research on the whole indicates a performance benefit for those involved in short-term high intensity exercise. Creatine appears to be effective at increasing muscle strength and size when combined with a resistance training programme.

9/10 for high intensity short-term exercise

References

1.  Casey A., Constantin-Teodosiu D. and Howell. Creatine ingestion favourably affects performance and muscle metabolism during maximal exercise in humans. Am J Physiol. 271:E31-E37, 1996.
2.  Harris R.C., S?lund K. and Hultman E. Elevation of creatine in resting and exercise muscle of normal subjects by creatine supplementation. Clin Sci. 83:367-374, 1992.
3.  Hultman E., S?lund K. and Timmons J.A. Mucle creatine loading in men. J Appl Physiol. 81:232-237, 1996.
4.  Becque M.D., Lochmann J.D. and Melrose D.R. Effects of oral creatine supplementation on muscular strength and body composition. Med Sci Sports Exerc. 32:654-658, 2000.
5.  Bosco C., Tihanyi J. and Pucspk J. Effect of oral creatine supplementation on jumping and running performance. Int J Sports med. 18:369-372, 1997.
6.  Izquierdo M., Ib?z J. and Gonz?z-Badillo J.J. Effects of creatine supplementation on muscle power, endurance, and sprint performance. Med Sci Sports Exerc. 34:332-343, 2002.
7.  Jowko E., Ostszewski P. and Jank M. Creatine and B-hydroxy-B-methylbutyrate (HMB) additively increase lean body mass and muscle strength during a weight-training program. Nutrition. 17:558-566, 2001.
8.  Kreider R.B., Ferreira M. and Wilson M. Effects of creatine supplementation on body composition, strength, and sprint performance. Med Sci Sports Exerc. 30:73-82, 1998.
9.  Stout J., Eckerson J. and Ebersole K. Effect of creatine loading on neuromuscular fatigue threshold. J Appl Physiol. 88:109-112, 2000.
10.  Tarnopolsky M.A. and MacLennan D.P. Creatine monohydrate supplementation enhances high-intensity exercise performance in males and females. In J Sport Nut. 10:452-463, 2000.
11.  Volek J.S., Duncan N.D. and Mazzetti S.A. Performance and muscle fibre adaptations to creatine supplementation and heavy resistance training. Med Sci Sports Exerc. 31:1147-1156, 1999.
12.  Kamber M., Koster M. and Kreis R. Creatine supplementation, Part I: performance, clinical chemistry, and muscle volume. Med Sci Sports Exerc. 31:1763-1769, 1999.
13.  Shomrat A., Weinstein Y. and Katz A. Effect of creatine feeding on maximal exercise performance in vegetarians. Eur J Appl Physiol. 82:321-325, 2000.
14.  Skare O.C., Skadberg ? and Wisnes A.R. Creatine supplementation improves sprint performance in male sprinters. Scand J Med Sci Sports. 11:96-102, 2001.
15.  Maganaris C.N. and Maughan R.J. Creatine supplementation enhances maximum voluntary isometric force and endurance capacity in resistance trained men. Acta Physiol Scand. 163:279-287, 1998.
16.  McNaughton L.R., Dlaton B. and Tarr J. The effects of creatine supplementation on high-intensity performance in elite performers. Eur J Appl Physiol. 78:236-240, 1998.
17.  Burke L.M., Pyne D.B. and Telford R.D. Effect of oral creatine supplementation on single-effort sprint performance in elite swimmers. Int J Sport Nutr. 6:222-233, 1996.
18.  Cooke W.H., Grandjean P.W. and Barnes W.S. Effect of oral creatine supplementation on power output and fatigue during bicycle ergometry. J Appl Physiol. 78:670-673, 1995.
19.  Redondo D.R., Dowling E.A. and Graham B.L. The effect of oral creatine monohydrate supplementation on running velocity. Int J Sport Nutr. 6:213-221, 1996.
20.  Snow R.J., McKenna M.J. and Selig S.E. Effects of creatine supplementation on sprint performance and muscle metabolism. J Appl Physiol. 84:1667-1673, 1998.
21.  Nissen S.L. and Sharp R.L. Effect of dietary supplements on lean mass and strength gains with resistance exercise: a meta-analysis. J Appl Physiol. 94:651-659, 2002.