CMM and WJK designed the study protocol. ECL, LMY, DLH, BLB, and BPM made substantial contributions to data acquisition. LEA and JSV made substantial contributions to interpretation of data. ECL performed the statistical analysis and was primarily responsible for writing the manuscript. CMM, WJK, LMY and SASC were also involved in manuscript writing and preparation. All authors have read and approved the final manuscript.”
“Background Muscle creatine phosphate content has been shown to decline during prolonged exercise at 70% VO2max [1, 2]. It is also well-established that dietary creatine supplementation High Content Screening can increase muscle creatine phosphate content and creatine phosphate

resynthesis rates; thereby improving high-intensity intermittent exercise performance [3–6]. However, it is not known if creatine supplementation prior to exercise can elevate muscle total creatine and creatine phosphate content sufficiently to maintain muscle creatine phosphate content above those in a non-supplemented condition throughout prolonged endurance exercise. Increased muscle creatine phosphate content at the end of endurance exercise may improve performance of a final sprint to exhaustion at the end of endurance exercise because

creatine phosphate is a major source of ATP for muscle ATP hydrolysis Selleck EVP4593 during short duration (< 30s) maximal-intensity efforts [7]. There are conflicting data as to whether or not creatine ingestion results in improved performance of prolonged exercise [8–12]. There have to date been five studies of the effects of creatine ingestion on performance of exercise lasting longer than 20 minutes. Three of these NADPH-cytochrome-c2 reductase studies demonstrated improved performance of either continuous prolonged exercise (1 hour time trial) or of intermittent sprints following prolonged exercise [8–10]. Two other studies reported no change, or a decrement in performance following: a) a 25 kilometer cycling

time trial interspersed with 15-second sprints [11] or b) a one hour time trial on a cycle ergometer [12]. Some of the studies were not double blind, randomized, or performed with a placebo; furthermore, muscle biopsies were obtained to document increased muscle creatine phosphate stores in only one of these previous studies. Exercise in these previous studies was performed following 5-7 days ingestion of 20 grams per day of a creatine supplement. There is sufficient evidence that creatine ingestion of 20 grams per day over five days increases muscle creatine phosphate content and increases performance of find more repeated short bouts of high-intensity intermittent exercise [3, 13–15]. Chronic, rather than short-term (less than one week), creatine supplementation is more commonplace in athletes, yet little is known of the effects of chronic creatine supplementation on muscle creatine phosphate levels and performance.