by Brendan Gabriel
Creatine (Cr) occurs naturally in the diet in foods such as meat, poultry and fish. The body only synthesises 1g of protein a day, from non-essential amino acids. Cr supplementation is believed to improve performance in strength and power activities, and provides the means for a greater muscle overload during training, increasing training effects.
Cr was believed to be responsible for reduced insulin sensitivity, however Newman et al.(2003) found this not to be the case at levels of 20g/day ingestion over 28 days(n=17)
Taking creatine in its most widely used supplement form –creatine monohydrate- has the benefit of increasing intramuscular concentrations of free Cr and creatine phosphate (PCr) by up to 20%. This is when is it taken at a relatively high dosage of 20g per day(n=31). (Hultman et al. 1996)
Preen et al. (2001) found that the increase in intramuscular Cr also increases sprint exercise performance. 14 healthy but untrained men were given 20g/day of Cr for 5 days. The subjects performed 10 sets of either 5 or 6 × 6 s maximal bike sprints, with varying recoveries, before and after Cr supplementation. Total work done increased significantly (P < 0.05) from 251.7 ± 18.4 kJ pre-supplementation to 266.9 ± 19.3 kJ (6% increase) after Cr ingestion. Volek et al. (2001) also found an increase in sprint cycling performance after Cr supplementation.
Cr supplementation has also been shown to increase lean body mass. Kreider et al. (1999) found that after 28 days of 15.75 g/day of Cr ingestion, lean body mass significantly increased(P < 0.05) by 2.42 ± 1.4 kg (n=25). Originally findings such as these were attributed to the increased water retention due to the osmotic effects of Cr in the cell. However this study found that there was no increase in the percentage of body water. A study by Earnest et al. (1995) also had similar findings.
Again in the study by Volek et al. (2001) found that Cr supplementation combined with heavy resistance training over 12 weeks significantly increases Type I (35% vs 11%), IIA (36% vs 15%), and IIAB (35% vs 6%) muscle fibre cross-sectional areas, compared with a placebo group (n=10).
The mechanisms for these changes with Cr supplementation combined with resistance training are not fully understood but are believed to be because of the possibility of higher training intensity with Cr supplementation. Some of the mechanisms hypothesized to be involved with this process and the increased performance in power events are; an increase in intramuscular Cr and PCr; an increased hydration of the cell; decreased dependence on glycolosis; decrease in cellular lactate and H+; an increase in PCr re-synthesis. These mechanisms delay the onset of fatigue and increase short-term muscular performance. Combined with resistance training this can make it possible for an increase in training intensity. This is believed to be the cause of increased protein synthesis in the body and increases in the diameter of muscle fibres and lean body mass. (McArdle et al., 2006)
In summary it appears that Cr supplementation would be beneficial for athletes performing repeated bouts of sprint or power activity because of the short-term effect of increased PCr and CR intramuscular levels. This increase shows increased performance due to a possible decreased reliance on glycolosis and delayed onset of fatigue. These results were shown best when supplementation levels were around 20-30g/d. effects were noticed after as little as 5 days.
It also appears that a longer term effect over a month or longer, is the increase in protein synthesis in the body when Cr supplementation and resistance training were combined. This increase in protein synthesis was shown most in the increased diameter of type II skeletal muscle fibres. This is believed to be due to an increased in possible training intensity leading to bigger adaptations. Again best results were shown at around 20-30 g/day. However effects were shown with only 10g/day.