Metabolic and exercise endurance effects of coffee and caffeine ingestion

Caffeine (Caf) ingestion increases plasma epinephrine (Epi) and exercise endurance; these results are frequently transferred to coffee (Cof) consumption. We examined the impact of ingestion of the same dose of Caf in Cof or in water. Nine healthy, fit, young adults performed live trials after ingesting (double blind) either a capsule (Caf or placebo) with water or Cof (decaffeinated Cof, decaffeinated with Caf added, or regular Cof). In all three Oaf trials, the Caf dose was 4.45 mg/kg body wt and the volume of liquid was 7.15 ml/kg. After 1 h of rest, the subject ran at 85% of maximal O-2 consumption until voluntary exhaustion (similar to 32 min in the placebo and decaffeinated Cof tests). In the three Caf trials, the plasma Caf and paraxanthine concentrations were very similar. After Ih of rest, the plasma Epi was increased (P < 0.05) by Caf ingestion, but the increase was greater (P < 0.05) with Oaf capsules than with Cof. During the exercise there were no differences in Epi among the three Caf trials, and the Epi values were all greater (P < 0.05) than in the other tests. Endurance was only increased (P ( 0.05) in the Oaf capsule trial; there were no differences among the other four tests. One cannot extrapolate the effects of Oaf to Cof; there must be a component(s) of Cof that moderates the actions of Caf.