Diverting some of the blood flow also assures the most efficient flow of cardiac output through the exercising muscle. In a similar manner, the release of endogenous ATP from cardiomyocytes

occurs in response to ischemia [16], thus resulting in increased blood flow and increased oxygen and glucose delivery to the active muscle tissue. These observations lead to the hypothesis that dietary supplementation with ATP (and/or adenosine) should be beneficial to exercising muscle tissue. However, it should be noted that it is unlikely that ATP is absorbed intact in humans [17, 18] and the effect of oral ATP on muscle performance is likely due to the previously described Cell Cycle inhibitor purinergic signaling [2] or through ATP metabolites such as adenosine [12, 19]. Supporting this hypothesis of purinergic signaling, Calbet et al. demonstrated that infusion of ATP at near-maximal exercise resulted in increased blood flow to less-active and non-muscle LDC000067 nmr tissues [20]. Improving blood flow through less active muscle tissues could remove waste products such as lactate. Additionally, Jordan et al. demonstrated that orally ingested ATP may be metabolically available to tissues and may influence adenine nucleotide metabolism during exercise [21]. The study showed that oral supplementation with ATP (225 mg) for 14 days resulted

in increased within group set-one repetitions and increased total lifting volume on the bench press apparatus; however, no effect was observed at the lower dosage of 150 mg ATP per day. The current study

was designed to test the hypothesis that supplemental CBL0137 nmr ATP would improve performance of repeated high intensity exercise as measured by muscle torque, power, work and fatigue. Methods Sixteen volunteers (8 male and 8 female; ages: 21–34 years) were enrolled in a double-blinded, placebo-controlled study using a crossover design. The protocol followed during each supplementation and testing period is shown in Figure 1. Both the placebo capsules containing rice flour and the ATP capsules containing 200 mg of Peak ATP® were obtained from a commercial manufacturer (TSI (USA), Inc., Missoula, MT). The ATP supplement was delivered as the disodium salt. A daily dosage of 400 mg/d was utilized for the current study and was chosen because Sulfite dehydrogenase the 225 mg ATP/d dosage used by Jordan et al. failed to improve bench press strength compared with the placebo group [21], and we reasoned that a higher dosage may be necessary to demonstrate an effect of oral ATP on knee extension fatigue and strength. A washout period of at least 1 week separated the experimental trials. For each of the trials, participants consumed their assigned capsules for 15 days as previously described. After the supplementation period, the participants reported to the laboratory for testing after an overnight fast of 12 h.