Figure 3 summarizes the results for endurance; caffeine capsule ingestion resulted in a significant increase in endurance time of 7.5-10 min compared with the other four trials. Six subjects had their longest run of all five trials after ingestion of caffeine capsules, seven had longer runs after caffeine compared with placebo capsules, and eight ran longer after caffeine ingestion compared with after they drank decaffeinated coffee. In sharp contrast, there were no differences among the three trials in which coffee was ingested, and the results were not different from the placebo capsule trial. This is surprising in light of the remarkably similar data for plasma caffeine and paraxanthine concentrations for the three caffeine trials. Within the three trials with coffee beverages, there was no consistency in performance time and no apparent tendency for any one beverage to produce an ergogenic effect. For example, within these trials, three subjects had their longest run after decaffeinated coffee, whereas the other six subjects were equally divided between the other two caffeinated beverages.
Bookmarks