Synergestic Effects of Magnesium and Creatine on Ergogenic Performance in Rats

H. Dewayne Ashmead, PhD*

Alain Bourdonnais, DVM†

Stephen D. Ashmead, MS*

Albion Advanced Nutrition

*Clearfield, Utah

†St. Brieuc, France

KEY WORDS: Ergogenic activity, magnesium creatine, chelate, magnesium bis-glycine chelate, creatine, magnesium.

Abstract

Supplements of either magnesium or creatine have been previously reported to improve ergogenic performance. This study compared ergogenic activity and recovery in rats by swimming them to exhaustion, resting them for 30 minutes, and then re-swimming them to exhaustion after previously receiving no creatine supplementation, creatine monohydrate (CM) alone, CM plus MgO, CM plus Mg amino acid chelate, or Mg creatine chelate supplements for 8 days. Daily doses of Mg and creatine were 5 mg and 100 mg, respectively, per kg body weight. The source of the Mg appeared to affect ergogenic performance. The Mg creatine chelate not only resulted in significantly (P < 0.01) greater swimming time to exhaustion, but it was the only Mg source that resulted in significant (P < 0.05) ergogenic recovery during the second swimming period. It was concluded that when Mg was chelated to CM in a 1:1 molar ratio, the resulting molecule allowed greater ergogenic activity than when the metabolites were supplied as admixtures with Mg coming from other sources.

Introduction

Creatine is synthesized by the renal transamidination of arginine to glycine to form guanidoacetic acid (glycocyamine) followed by hepatic methylation of that glycocyamine by active methionine (S-adenosyl L-methionine).1 After synthesis, it is absorbed into muscle cell mitochondria, where it is phosphorylated into creatine phosphate by magnesium activated creatine kinase (Figure 1).2–6 After it is phosphorylated, creatine phosphate leaves the mitochondria and travels to the contractile proteins of the muscle fiber.

On contraction of myofibrils, hydrolysis of ATP to ADP occurs, subsequently releasing sufficient energy to sustain the myofibrils for approximately 10 seconds. Continued contraction requires additional energy derived from the dephosphorylation of creatine phosphate by magnesium-activated creatine kinase (Figure 1).5

During dephosphorylation, not all of the creatine phosphate reverts back to creatine. Some of it spontaneously degrades into creatinine (Figure 1). It is estimated that approximately 1.7 g creatinine is produced daily and excreted via the urine.2,5 Because of the greater creatine phosphate requirements of an athlete, athletes generally excrete more than 1.7 g, depending on the type of sport performed, the intensity of the physical activity, and muscle mass.7 In any case, the body has a continued need for additional creatine from either metabolic synthesis or exogenous sources.

Several investigators have reported that creatine supplementation enhances ergogenesis during repeated bouts of maximum intensity exercise.8,9 Additionally, Harris et al.10 found that whereas the ingestion of 1 g of creatine monohydrate resulted in only slight increases of blood creatine, 5 g of creatine resulted in significant increases. Concurrently, they showed that when the subjects exercised, there was greater retention of absorbed creatine. These results point to a mechanism that possibly regulates absorption of exogenic creatine. Other research suggests, however, that absorption and retention of dietary creatine may be more a function of physical activity than quantity ingested.11

Although most metabolic investigations have focused on creatine phosphate or ATP when considering muscle energy, it is important to not overlook the potential significance of magnesium. Stending-Lindberg et al.12 reported that high muscle magnesium significantly (P < 0.001) improved endurance during strenuous exercise. Other clinical and experimental data also suggest that oral magnesium supplementation enhances performance in athletes.13,14 Although acknowledging magnesium’s role in ergogenics, researchers have not reached total agreement on the value of supplemental magnesium. Some investigators have reported that oral magnesium supplementation had little effect on intramuscular magnesium concentrations, which suggests that the current magnesium status of the body will influence magnesium uptake.12,15

The source of the magnesium may have also impacted the magnitude of the effect of magnesium supplementation noted by these researchers. Different magnesium sources have different bioavailabilities. Limited data from animal studies suggest greater absorption of magnesium from an amino acid chelate source compared with MgO, MgSO₄ or MgCl₂.16–18 Investigators reported greater magnesium tissue uptakes from an oral dose of magnesium bisglycine chelate than with inorganic magnesium salts in human volunteers.19,20

In ergogenic studies involving animals, employment of different sources of magnesium has resulted in significant variations in physical performance. When dietary magnesium was provided as an amino acid chelate rather than as an inorganic salt, individual rats had a 2.5 times longer mean swimming time.21 In a similarly designed study, magnesium was fed as either a magnesium aspartate salt or as a magnesium aspartate chelate. Swimming time was increased twofold (P < 0.05) when the source of the magnesium was the aspartate chelate compared to the aspartate salt.22

Although magnesium and creatine have been studied individually, little has been published on the ergogenic effect of supplementing magnesium and creatine concurrently. The kinetic studies of Kuby et al.23 do not address supplementation but have reported that the level of creatine kinase activity depends on the ratio of magnesium to creatine as well as the concentration of each. Maximum creatine kinase activity was achieved at a 1:1 molar ratio of magnesium to creatine. An excess of either metabolite was inhibitory to the total kinase activity.23

The purpose of this study was to determine the swimming time to exhaustion before and after a recovery period in rats that received no supplemental magnesium or creatine compared with groups of rats that received supplements of creatine monohydrate alone, creatine monohydrate plus MgO, creatine monohydrate plus magnesium bisglycine chelate, or magnesium creatine chelate.

Materials and Methods

The study design called for five groups of 10 each male Sprague-Dawley rats of similar age and weighing 210 ± 10 g each. The animals were statistically the same as determined by analysis of covariance. The animals were housed in groups of five each in polypropylene cages (floor area 1,032 square cm) under standard laboratory conditions. Ambient room temperature was maintained at 31˚C ± 1˚C to preclude the need for energy to be produced for body heat.24

Each group of animals received food and water ad libitum. The rat feed was prepared by Extralabo and met the NRC criteria for growing rats. It was granular (15 mm diameter) in composition and supplied 150 g of protein and 0.5 g magnesium (MgO) per kg of feed. Supplemental magnesium (5 mg/kg bw) and/or creatine (100 mg/kg bw) were also administered in the feed as described subsequently. Equating these dosages to human requirements, the United States RDA for magnesium in humans was met and approximately 5 times the amount of exogenic creatine required by a 70 kg sedentary person per day was supplied. The molar ratio of supplemental magnesium to supplemental creatine was 1:1. Except for the control group, the final concentrations of supplemental magnesium and creatine were identical for each treatment group.

Group 1, the control group, received no supplemental creatine or magnesium. Group 2 received creatine monohydrate (88.1% purity) without any supplemental magnesium. Group 3 received the same amount and type of creatine monohydrate admixed with MgO. Group 4 also received the same source and quantity of creatine monohydrate, but the source of magnesium admixed with this creatine came from magnesium bisglycine chelate.25 Group 5 received magnesium creatine chelate in which magnesium was chelated to the same source of creatine monohydrate in a one-to-one (magnesium:creatine) molar ratio (Figure 2) as confirmed by FT-IR analysis.26

This magnesium creatine chelate molecule had previously been found not to interfere with creatine kinase activity.27 The LD50 dose of magnesium creatine chelate had previously been determined to be in excess of 5,000 mg/kg body weight. The LD50 doses for the sources of the magnesium used in the admixtures and as well as the LD50 does for the creatine alone have all been reported to be quite high. Thus, the approximate daily dosage of 5 mg of magnesium and 100 mg creatine/kg body weight was not considered to be potentially toxic.28

All of the rats in groups 1 through 5 were allowed to habituate for 7 days after random placement in their cages. The magnesium-creatine supplementations for groups 2 through 5 were initiated on day 8 and continued through day 15. Physical performances of all rats in all groups were determined only on day 17 to avoid any endurance training—mediated effects or to artificially increase the absorption of dietary creatine due to increased physical activity. All rats were fasted for 24 hours before swimming.

After the procedure reported by Ellis et al.,22 each rat was placed in a tank measuring 90 cm in diameter and 70 cm deep, filled with water in which the temperature was maintained at 30˚C ± 1˚C. Each rat was exercised in its individual tank in series of 5 (one rat from each of the experimental groups) to maintain high comparability between groups. To keep the animals swimming continuously and reduce the time it took for each to reach exhaustion, each had a weight attached to its tail, which was equivalent to approximately15% of its body weight. All of the rats observed by an individual who was blinded to the treatments.

A second swim test to exhaustion was performed after a fixed recovery interval of 30 minutes. Harris et al.29 previously reported that metabolic production of new creatine phosphate requires a recovery time of at least 20 minutes. Each rat maintained the weight on its tail from the previous test. The handler continued to be blind as to the treatments.

SAS software was used for statistical analysis. Statistical tests were performed with an alpha level of 0.05. For swimming times, one-way analysis of variance (ANOVA) was performed for each swim test. Correlations between the two tests were calculated for each group. When a significant group effect was detected, multiple ANOVA and 2-way univarient analysis were used to compare the differences between the groups.

Results

Most of the supplements appeared to affect ergogenic performance. Table 1 summarizes the mean time each group of rats swam to exhaustion during the first and second swimming periods. The differences between these times (DT1 and DT2) are the total mean increased amounts of time and the percentage increases that the rats in each of the experimental groups could swim compared with the control group. The last column provides the net percentage increases of each group compared with the control group.

The rats receiving creatine alone (group 2) or magnesium bisglycine chelate plus creatine (group 4) were able to swim significantly longer (P < 0.05) in the first period (T₁) than the rats in group 1 (the control group). Rats in group 5, the magnesium creatine chelate group, also swam significantly longer in the first period (T₁) than the control group (P < 0.01). Multiple ANOVA indicated no significant differences in the first period swimming times between these three supplemented groups. The swimming time of group 3, which received creatine plus MgO, during the first period (T₁) was not significantly greater than that of the control group.

During the second swimming period (T₂), groups 2, 4, and 5 were all able to swim significantly longer (P < 0.05) than the control group (group 1). Group 3 (creatine plus MgO) was not significantly different than the control group (group 1). There was also a significant (P < 0.05) net percentage difference between the first and second swimming times of Group 5 compared with those of the other groups (Column 5).

In an attempt to suggest the rate of production of new creatine phosphate from metabolic and exogenous sources of creatine, Table 2 shows the recovery (or lack thereof) from period 1 to period 2 (T₂–T₁) and the percentage of recovery for each group (T₂/T₁ x 100). As a percentage of recovery, no significant differences were seen among groups 1, 2, 3, and 4. However, a significant difference (P < 0.05) was seen in the recovery rate of group 5.

Table 3 ranks groups 2 through 5 by calculating the mean ergogenic differences between the control group and each of the experimental groups in each of the two swimming periods, then totaling these mean differences by group, and finally ranking them from highest to lowest. Group 5 had the greatest improvement over the control group at 146%, followed by group 2, group 4, and group 3. The creatine group, group 2, achieved 140% improvement. The creatine plus magnesium bisglycine chelate group, group 4, achieved 136% improvement. And finally, group 3, the creatine plus MgO group, achieved a 119% improvement over the total mean swimming time of the control group.

Discussion

This study shows that ergogenic improvements are possible when laboratory rat diets were supplemented concurrently with creatine and magnesium. It also showed that the source of magnesium may affect ergogenic activity. When creatine was supplemented alone, physical performance increased 30.6% in the first period and 49.7% in the second period over the control. When magnesium oxide was added to the creatine, physical performance increased 14.1% in the first period and 24.1% in the second period over the control. This increase was less than the creatine alone. The admixing of magnesium as an bisglycine chelate with the creatine resulted in a 28.2% increase in physical performance in the first period and a 45.2% increase in physical performance in the second period compared with the control group. This was somewhat equivalent to the creatine alone. Finally, when chelated magnesium creatine was supplemented, the physical performance increased 36.2% in the first period and 57.6% in the second period compared with the control group. These variations may be due to variations in the bioavailability of the magnesium source. This should be the subject of further investigation

Although statistically the same, the admixing of magnesium oxide or magnesium bisglycine chelate to the creatine appeared to reduce ergogenic activity over creatine alone. Because of its lower bioavailability, MgO may not have supplied sufficient absorbed magnesium to maximize creatine kinase activity. Conversely, magnesium bisglycine chelate may have resulted in too much magnesium absorption to maximize the 1:1 magnesium:creatine optimum ratio, thus also potentially interfering with kinase activity. In vitro studies have shown that magnesium amino acid chelate is 5.4 times more bioavailable than MgO.30 This should perhaps also be the subject of additional investigation.

In this study, magnesium deficiencies were not artificially induced in the experimental animals. Consequently, their current magnesium tissue levels may have partially influenced the outcome of creatine supplementation regardless of whether it was supplied with or without magnesium and in whatever form. No attempt was made to ascertain magnesium tissue levels in any of the animals in this study. Magnesium tissue levels perhaps should be controlled in a future study.

Absorption and retention of exogenic creatine is, to a degree, a function of previous ergogenic activity. In this study no attempt was made to exercise or limit the physical activity of any of the animals before the swimming tests. Future studies should probably consider this aspect of creatine absorption and metabolism.

Although no analytical procedures were performed to ascertain magnesium or creatine tissue levels, this study suggests that magnesium creatine chelate may have been absorbed in greater quantities or at least deposited in the muscle in greater quantities because of the differences in ergogenic activity. As shown in Table 2, only the group receiving the magnesium and creatine as a single chelate molecule produced significant new amounts of energy after 30 minutes of rest. The recovery rates for groups 2 through 4 were statistically no different that for the control group that received no supplementation. Because of the significant differences between Group 5 compared to the other groups, additional absorption and metabolic studies for the magnesium creatine chelate are probably warranted.

Conclusions

This study suggests that ergogenic activity may be enhanced when magnesium and creatine are chelated together in a 1:1 molar ratio and subsequently ingested as a single molecule compared with equivalent amounts of magnesium from either MgO or magnesium bisglycine chelate admixed to creatine monohydrate. Furthermore, creatine monohydrate alone did not produce equivalent ergogenic results to those produced by magnesium creatine chelate.

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Table 1. Increased Swimming Times of Supplemented Groups Compared With Nonsupplemented Groups

                                                                                                                                                   Net %
                                                                                                                                                  increase
                                                          Mean T₁ (sec)                                   Mean T₂ (sec)            over
                                  Swim 1              (% increase)              Swim 2             (% increase)           control
Group                      Time (sec)           over control           Time (sec)          over control       (%T₂ – % T₁)

1 178.8 ± 10.1 158.0 ± 5.9

(Control)

2 233.7* ± 16.2 54.8 (30.6) 234.02* ± 7.1 78.5 (49.7) 19.1
(Creatine)

3 204.0 ± 14.4 25.2 (14.1) 196.0 ± 24.4 38.0 (24.0) 9.9
(Creatine + MgO)

4 229.3* ± 20.1 50.5 (28.2) 229.4* ± 27.9 71.4 (45.2) 17.0
(Creatine + Mg AA Chelate)

5 Mg 243.6** ± 13.4 64.8 (36.2) 249.0* ± 9.8 91.0 (57.6) 21.4*
(Mg Creatine Chelate)

*P < 0.05.

**P < 0.01.

Table 2. Effect of Creatine and Magnesium Supplementation on Recovery

T₁ Swim 1 T₂ Swim 2 Change T₂-T₁ % Recovery
Group Time (sec) Time (sec) (sec) (T₂/T₁ x100)

1 (Control) 178.8 158.0 -20.8 88%

2 (Creatine) 233.6 236.5 2.9 101%

3 (Creatine + MgO) 204.0 196.0 -8.0 96%

4 (Creatine + Mg/Chelate) 229.3 229.4 0.1 100%

5 (Mg/Creatine Chelate) 243.6 249.0 5.4 02%*

*P < 0.05.

Table 3. Group Performance Improvement Ranking Over Control Group

Total % T₁ 1st Swim T₂ 2nd Swim Total Increase Improvement

Group (Sec) (Sec) Over Control (Sec) Over Control

5 (Mg/Creatine Chelate) 64.8 91.0 155.8 146

2 (Creatine) 54.8 78.5 133.3 140

4 (Creatine + Mg AA Chelate) 50.5 71.4 121.9 136

3 (Creatine + MgO) 25.2 38.0 63.2 119

*P < 0.05.

Figure 1. The bonding of creating to a phosphate group from ATP and the subsequent dephosphorylation of creatine phosphate back to creatine or degradation to creatinine.

Figure 2. Synthesis of magnesium creatine chelate. A hydrogen is removed from the hydroxyl moiety in the creatine. A soluble magnesium salt is iodized and the magnesium ion and creatine brought together. The magnesium is bonded to the creatine by covalent bonds with a resulting ring structure.