Graham and Spriet [8] examined varying doses of caffeine consumption at 3, 6, and

9 mg/kg on endurance capacity GSK461364 solubility dmso (run to exhaustion at 85% VO2max). Results from this study demonstrated an enhancement in performance, but only with the 3 and 6 mg/kg dose. Concurrently, the 6 and 9 mg/kg dosages were the only measured quantities that resulted in increased plasma epinephrine levels, with significant increases in glycerol and free fatty acids measured only at the 9 mg/kg dose. Therefore, results of this investigation present quite a paradox in that a low dose of caffeine (3 mg/kg) was adequate for enhancing performance, but did not lead to increased levels of epinephrine or subsequent effect of free fatty acid mobilization. Hulston and Jeukendrup [55] published data that indicated caffeine at 5.3 mg/kg co-ingested with a 6.4% glucose solution had no significant effect on increasing plasma FFA levels or glycerol concentrations, nor did it substantially enhance rates of whole-body fat oxidation during

endurance exercise even though performance was significantly improved with the caffeine + glucose solution [55]. Therefore, the results of some research studies lend substantiation to the premise that caffeine may act to increase performance by altering substrate utilization [16, 18], while results of additional investigations serve to suggest other mechanisms of action [50, 56, 57]. Carbohydrate consumption during exercise can decrease the body’s dependence on endogenous carbohydrate stores and lead to enhanced

endurance Blebbistatin datasheet performance [58, 59]. Therefore, it is beneficial to determine an optimal method of enhancing rates of exogenous carbohydrate delivery and oxidation. Exogenous carbohydrate delivery is determined by various factors including, but not limited to, the rate of gastric emptying and intestinal Batimastat in vitro absorption [58]. However, it has been suggested that during exercise intestinal absorption seems to have the greatest influence on the rate of exogenous carbohydrate oxidation [58, 60]. In 1987 Sasaki et al. [61] reported that in trained distance runners 100 g sucrose in combination with approximately 400 mg (~6 mg/kg) of caffeine had no additive effect on Aspartate endurance performance, when compared to consumption of either substrate alone. In addition, Jacobson et al. [62] reported that caffeine (6 mg/kg) combined with carbohydrate (2.6 g/kg), had no significant enhancement on exercise performance or substrate utilization in trained cyclists. However, Yeo et al. [63] reported that during the final 30 min of a 2-hr steady state bout of cycling (64% V02max) a 5.8% glucose solution (48 g/hr), in addition to 5 mg/kg of caffeine, significantly enhanced exogenous carbohydrate oxidation (~26% higher than glucose alone). It was suggested by these authors [63] and others [64] that this was the result of enhanced intestinal glucose absorption. Finally, Hulston et al.