phosphocreatine and Muscle-Cramp

Creatine has become a popular nutritional supplement among athletes. Recent research has also suggested that there may be a number of potential therapeutic uses of creatine. This paper reviews the available research that has examined the potential ergogenic value of creatine supplementation on exercise performance and training adaptations. Review of the literature indicates that over 500 research studies have evaluated the effects of creatine supplementation on muscle physiology and/or exercise capacity in healthy, trained, and various diseased populations. Short-term creatine supplementation (e.g. 20 g/day for 5-7 days) has typically been reported to increase total creatine content by 10-30% and phosphocreatine stores by 10-40%. Of the approximately 300 studies that have evaluated the potential ergogenic value of creatine supplementation, about 70% of these studies report statistically significant results while remaining studies generally report non-significant gains in performance. No study reports a statistically significant ergolytic effect. For example, short-term creatine supplementation has been reported to improve maximal power/strength (5-15%), work performed during sets of maximal effort muscle contractions (5-15%), single-effort sprint performance (1-5%), and work performed during repetitive sprint performance (5-15%). Moreover, creatine supplementation during training has been reported to promote significantly greater gains in strength, fat free mass, and performance primarily of high intensity exercise tasks. Although not all studies report significant results, the preponderance of scientific evidence indicates that creatine supplementation appears to be a generally effective nutritional ergogenic aid for a variety of exercise tasks in a number of athletic and clinical populations.

Topics: Adolescent; Adult; Creatine; Creatinine; Dietary Supplements; Energy Metabolism; Exercise; Female; Football; Humans; Male; Muscle Cramp; Muscle, Skeletal; Nutritional Physiological Phenomena; Phosphocreatine; Running; Time Factors

Suboptimal mitochondrial function has been implicated in several disorders in which fatigue is a prominent feature. Vitamin D deficiency is a well-recognized cause of fatigue and myopathy. The aim of this study was to examine the effects of cholecalciferol therapy on skeletal mitochondrial oxidative function in symptomatic, vitamin D-deficient individuals.. This longitudinal study assessed mitochondrial oxidative phosphorylation in the gastrosoleus compartment using phosphorus-31 magnetic resonance spectroscopy measurements of phosphocreatine recovery kinetics in 12 symptomatic, severely vitamin D-deficient subjects before and after treatment with cholecalciferol. All subjects had serum assays before and after cholecalciferol therapy to document serum 25-hydroxyvitamin D (25OHD) and bone profiles. Fifteen healthy controls also underwent (31)P-magnetic resonance spectroscopy and serum 25OHD assessment.. The phosphocreatine recovery half-time (τ1/2PCr) was significantly reduced after cholecalciferol therapy in the subjects indicating an improvement in maximal oxidative phosphorylation (34.44 ± 8.18 sec to 27.84 ± 9.54 sec, P < .001). This was associated with an improvement in mean serum 25OHD levels (8.8 ± 4.2 nmol/L to 113.8 ± 51.5 nmol/L, P < .001). There was no difference in phosphate metabolites at rest. A linear regression model showed that decreasing serum 25OHD levels was associated with increasing τ1/2PCr (r = -0.41, P = .009). All patients reported an improvement in fatigue after cholecalciferol therapy.. Cholecalciferol therapy augments muscle mitochondrial maximal oxidative phosphorylation after exercise in symptomatic, vitamin D-deficient individuals. This finding suggests that changes in mitochondrial oxidative phosphorylation in skeletal muscle could at least be partly responsible for the fatigue experienced by these patients. For the first time, we demonstrate a link between vitamin D and the mitochondria in human skeletal muscle.

Topics: Adolescent; Adult; Cholecalciferol; Fatigue; Female; Humans; Longitudinal Studies; Magnetic Resonance Spectroscopy; Male; Middle Aged; Mitochondria; Muscle Cramp; Muscle, Skeletal; Oxidative Phosphorylation; Phosphocreatine; Phosphorus Isotopes; Treatment Outcome; Vitamin D Deficiency; Vitamins; Young Adult

Topics: Adenosine Triphosphate; Animals; Disease Models, Animal; Fructosediphosphates; Glycogen; Glycolysis; Hexosediphosphates; Lactates; Lactic Acid; Male; Muscle Contraction; Muscle Cramp; Muscles; Myoglobinuria; Phosphocreatine; Physical Exertion; Rats; Rats, Inbred Strains

Topics: Adenine Nucleotides; Adenosine Triphosphate; Blood Chemical Analysis; Contracture; Electromyography; Glycogen; Humans; In Vitro Techniques; Lactates; Metabolism, Inborn Errors; Muscle Contraction; Muscle Cramp; Muscle Proteins; Muscles; Muscular Diseases; Myoglobinuria; Phosphocreatine; Phosphotransferases; Physical Exertion; Spectrophotometry