Two Levels of Caffeine Ingestion on Blood Lactate and Free Fatty Acid Responses during Incremental Exercise

Abstract

Caffeine has been used as an ergogenic aid by long distance runners and cyclists. This research was conducted to determine the effects of two doses of caffeine on the lactate threshold and to examine, using respiratory data, the effects on substrate utilization during incremental cycle ergometry. Ten male subjects were used and were selected on the basis of their lack of caffeine consumed in their general diet. The incremental test consisted of cycling at 50 rpm at a given work rate for one minute after which the rate was increased by 30 kpm · mvn⁻¹ and was then held constant for another minute until exhaustion. Heart rate values during the caffeine trials were higher than the control values (p <.05) for all work loads. Blood lactate levels were lower (p <.05) for both caffeine trials at workloads below 1800 kpm · min⁻¹ while free fatty acid levels increased (p <.05) for all workloads during caffeine usage. The results suggest that both of the doses of caffeine were effective in increasing the amount of blood FFA and thus affected substrate utilization. Work time to exhaustion was also increased. This suggests that caffeine in high doses, could be used as an ergogenic aid during incremental exercise.