Caffeine is one of the famous ergogenic aids in the athletic field. Caffein
e has been known to stimulate lipolysis that spares stored glycogen utiliza
tion during moderate intensity exercise, Therefore, we investigated the eff
ects of caffeine ingestion on exercise performance in rats and athletes. Ra
ts were administered the caffeine (6 mg/kg) 1 h prior to the exercise then
were run on a treadmill at a speed of 20 m/min, They were decapitated at 0
min, 30 min, 60 min of exercise, and exhausted time point. Human subjects i
ngested the caffeine (5 mg/kg) 1 h prior to the exercise. They exercised on
a cycle ergometer at 60% of their VO2max for 45 min, and then the exercise
intensity was increased to 80% of their VO2max until exhaustion. Blood and
breathing gas samples were collected and calculated every 10 min during ex
ercise. Respiratory exchange ratio of the caffeine trial was significantly
lower than that of the placebo trial in the athletes' study (p<0.05). Blood
free fatty acid (FFA) levels in studies of both rats and athletes were inc
reased by caffeine ingestion during exercise (p<0.05). Blood lactate levels
were also increased during exercise in both rats and athletes (p<0.05). In
creased FFA and glycerol concentrations reduced glycogen utilization during
exercise compared with placebo group in rats. In addition, endurance time
to exhaustion was significantly increased by the caffeine ingestion in both
rats and athletes (p<0.05). These results suggest that the caffeine ingest
ion enhanced endurance performance resulting from spare stored glycogen wit
h increasing lipolysis from adipose tissues and fat oxidation during exerci
se both in rats and in athletes.