Creatine Monohydrate: A Sprint Performance Enhancer? - Triathlon Week

Robert G. · 02-07-2003, 01:18 AM

Phosphocreatine (PCr) and adenosine triphosphate (ATP) supply most of the energy for short term, maximal exercise. PCr availability is important for performance during brief, high power exercise because the depletion of PCr prevents ATP from being resynthesized at the rate required.

The average creatine content of skeletal muscle is 125 mmol/kg dm and ranges from about 90 to 160 mmol/kg dm. Approximately 60% of muscle creatine in is the form of PCr. The creatine moety of PCr may be obtained from dietary creatine (found primarily in meat products) or synthesized from the amino acids glycine and argnine. Muscle creatine is replenished at the rate of about 2 g/day, following its irreversible degradation to creatinine. Since creatine is a low molecular weight compound and removed by the kidneys via diffusion (a non-energy dependent process), creatine loading is unlikely to pose any health risk. Creatine loading is associated with an increase of in body weight and lean body mass of several kg, which is either due to fluid retention or enhanced skeletal muscle synthesis.

In theory, creatine supplementation elevates muscle creatine levels and facilitates the regeneration of PCr. Greenhaff notes that ingesting 20 g/day of creatine monohydrate (four doses of 5 g) for five days can produce a 20% increase in muscle creatine levels, of which about 20% is PCr (1). After this loading dose, a maintenance dose of 5 g/day should maintain elevated creatine levels.

The first creatine supplementation trials suggested that a single bout of high intensity exercise might be enhanced via increased muscle PCr availability (2) and that repeated bouts of exercise might be enhanced by an increased rate of PCr resynthesis during recovery (3).

Human muscle appears to have an upper limit of creatine storage of 150 to 160 mmol/kg dm. Athletes who have high muscle creatine stores won’t benefit from supplementation, whereas individuals with the lowest levels of muscle creatine have the most pronounced increases following supplementation. Vegetarians are likely to have low creatine stores and may be helped by supplementation (1).

Three recently published studies suggest that creatine monohydrate supplementation does not improve sprint performance (4, 5, 6). Redondo and colleagues evaluated the effect of creatine supplementation on running velocity during three 60 meter sprints (with two minutes rest between trials) that were recorded with videotape (4). The treatment group consumed 25 g/day of a creatine-glucose solution (five doses of 5 g) for seven days while the placebo group consumed a corresponding amount of a glucose solution. The creatine supplement did not improve running velocity during any filmed portion of any of the three 60 meter sprints. Muscle creatine levels weren’t measured and the subjects may not have responded due to high initial creatine stores.

Burke examined the effect of creatine supplementation on single-effort swim sprint performance in elite swimmers (5). The treatment group consumed 20 g/day of a creatine solution (four doses of 5 g) for five days while the placebo group consumed a corresponding amount of a glucose polymer solution. The creatine supplement did not improve swim sprint performance at 25, 50, or 100 meters. Muscle creatine levels weren’t measured and the subjects probably had high initial creatine stores. Also, muscle PCr may not be a limiting factor in a single swim sprint performance over 25 to 100 meters.

Odland and colleagues evaluated the effect of creatine supplemenation on muscle PCr and power output during a 30-s maximal cycling (Wingate) test (6). The treatment group consumed 20 g of creatine dissolved in a flavored drink (four doses of 5 g) for three days while the placebo group consumed the flavored drink only. The creatine supplement had no effect on peak power, mean 10-s power, mean 30-s power, percent fatigue or post-exercise blood lactate concentration. Although the creatine supplement significantly increased the ratio of total muscle creatine to ATP, it did not change the ratio of muscle PCr to ATP. A longer time period of creatine supplementation (five days) may be necessary to increase muscle PCr and improve sprint performance.

Volek and associates investigated the effect of creatine supplementation on muscular performance during repeated sets of high-intensity resistance exercise. The creatine and placebo group performed bench press and jump squat exercise protocols on three different occaisions (T1, T2, and T3) separated by 6 days. Before T1, both groups received no supplementation. From T1 to T2, both groups took a placebo. From T2 to T3, the creatine group consumed 25 g (five doses of 5 g) of creatine per day and the placebo group remained on the placebo. Creatine supplementation significantly increased peak power output during all five sets of jump squats and significantly improved the number of repetitions performed during all five sets of bench presses (7).

Creatine supplementation may be most effective in delaying fatigue during repeated bouts of high-intensity exercise. Greenhaff and colleagues used a repeated trial design of five bouts of 30 voluntary isokinetic leg extensions with a 60 second rest following five days of 20 g/day (four doses of 5 g) of creatine (3). Peak muscle torque was significantly greater during the final 10 contractions of bout one, throughout all of bouts two to four, and during contractions 11-20 in bout five. However, the peak torque on the first contaction was not affected by creatine loading. Thus, chronic supplementation may enhance the quality of the athlete’s training by improving recovery during repeated bouts of sprints (interval training.)

A significant percentage of users experience cramps and/or muscle spasms. The research so far has been done primarily on college males and may not apply to teenagers, older individuals, or women. There is also no long term safety data on creatine. The NCAA Committee on Competitive Safeguards and Medical Aspects of Sports has urged that research be done to determine whether long-term use is safe and whether certain individuals might be predisposed to negative side effects.

References

1. Greenhaff, PL. Creatine and its application as an ergogenic aid. Int. J. Sports Nutr. 5 (Supplement):S100-10, 1995.

2. Balsom, PD et al. Creatine supplementation and dynamic high-intensity intermittent exercise. Scand. J. Med. Sports Sci. 3:143-149, `993.

3. Greenhaff, PL et al. Influence of oral creatine supplementation on muscle torque during repeated bouts of maximal voluntary exercise in man. Clin. Sci. 84:565-571, 1993.

4. Redondo, DR et al. The effect of oral creatine monohydrate supplementation on running velocity. Int. J. Sports Nutr. 6:213-221, 1996.

5. Burke, LM. Effect of oral creatine supplementation on single-effort sprint performance in elite swimmers. Int. J. Sports Nutr. 6:222-233, 1996.

6. Odland, LM. Effect of oral creatine supplementation on msucle (PCr) and short-term maximum power output. Med. Sci Sports Exerc. 29:216-219, 1997.

7. Volek et al. Creatine supplementation enhances muscular performance during high-intensity resistance exercise. J. Amer. Diet. Assoc. 97:765-770, 1997.

Ellen Coleman, RD, MA, MPH

Zylo · 09-19-2004, 02:05 PM

I love Creatine.

Seems to work for some people, and not for others.

It makes my muscles big and gives me tons of energy.

I suggest everyone tries it to see if they like it. I find the best use for it is when you are lifting heavy HEAVY weights and training really hard. I get crazy gains/benefits from using creatine. I always have most energy when I'm on creatine. I usually go on it and use up a jug of it. Then go off it for the same amount of time before using another.