Does dietary creatine supplementation play a role in skeletal muscle metabolism and performance?

Fatigue sustained during short-term, high-intensity exercise in humans is a ssociated with the inability of skeletal muscle to maintain a high rate of anaerobic ATP production from phosphocreatine hydrolysis. Ingestion of crea tine monohydrate at a rate of 20 g/d for 5-6 d was shown to increase the to tal creatine concentration of human skeletal muscle by approximate to 25 mm ol/kg dry mass, some 30% of this in phosphorylated form as phosphocreatine. A positive relation was then shown between muscle creatine uptake and impr ovements in performance during repeated bouts of maximal exercise. However, there is no evidence that increasing intake >20-30 g/d for 5-6 d has any p otentiating effect on creatine uptake or performance. In individuals in who m the initial total creatine concentration already approached 150 mmol/kg d ry mass, neither creatine uptake nor an effect on phosphocreatine resynthes is or performance was found after supplementation. Loss of ATP during heavy anaerobic exercise was found to decline after creatine ingestion, despite an increase in work production. These results suggest that improvements in performance are due to parallel improvements in ATP resynthesis during exer cise as a consequence of increased phosphocreatine availability Creatine up take is augmented by combining creatine supplementation with exercise and w ith carbohydrate ingestion.