Caffeine is ergogenic after supplementation of oral creatine monohydrate

Purpose: The purpose of this investigation was to assess the acute effects of caffeine ingestion on short-term, high-intensity exercise (ST) after a period of oral creatine supplementation and caffeine abstinence. Methods: Fourteen trained male subjects performed treadmill running to volitional exhaustion (T_lim) at an exercise intensity equivalent to 125% V̇O_2max. Three trials were performed, one before 6 d of creatine loading (0.3 g·kg^-1-d^-1; baseline), and two further trials after the loading period. One hour before the postloading trials, caffeine (5 mg·kg^-1) or placebo was orally ingested in a cross-over, double-blind fashion. Four measurements of rating of perceived exertion were taken, one every 30 s, during the first 120 s of the exercise. Blood samples were assayed for lactate, glucose, potassium, and catecholamines, immediately before and after exercise. Results: Body mass increased (P < 0.05) over the creatine supplementation period, and this increase was maintained for both caffeine and placebo trials. There was no increase in the maximal accumulated oxygen deficit between trials; however, total V̇O₂ was significantly increased in the caffeine trial in comparison with the placebo trial (13.35 ± 3.89 L vs 11.67 ± 3.61 L). In addition, caffeine T_lim (222.1 ± 48.9 s) was significantly greater (P < 0.05) than both baseline (200.8 ± 33.4 s) and placebo (198.3 ± 45.4 s) T_lim. RPE was also lower at 90 s in the caffeine treatment (13.8 ± 1.8 RPE points) in comparison with baseline (14.6 ± 1.9 RPE points). Conclusion: As indicated by a greater T_lim, acute caffeine ingestion was found to be ergogenic after 6-d of creatine supplementation and caffeine abstinence.