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.
