Abstract

The effects of an administration of a 50 cc watery solution containing either 30, 200, 300 mg of caffeine or a placebo were investigated on gas metabolism, cardiovascular activity, and glycolysis and lipolysis in 4 healthy, young male subjects during rest, and ergometer work at 60 (40 min), 80 (3 min) of VO2max and to exhaustion. The 30 mg dose of caffeine did not result in different reactions from the placebo at any workload, therefore its use, apart from the traces found in the blood and urine, is considered free. The 200 mg dose, inconsistantly, and the 300 mg dose, consistantly, produced results in respect to the placebo and to the 30 mg dose: No significant differences were found in the heart rate or marked increases in arterial pressure in either rest or at submaximal work loads. No changes were found in gas metabolism, in either the mechanical or ventilatory efficieny during work at 60-80 of VO2max. The continuation of work to exhaustion for a longer duration was found which allowed the completion of a higher-level of total work with a greater consumption of O2, higher O2 pulse, but with a light diminution of mechanical efficiency (poor motor coordination? use of prevalent lipids? better muscle tone?). A major use of lipids as energy sources, as demonstraded by a decrease in the R.Q. and by an elevation in the rate of emission of NEFA and glycerol. Simultaneously, however, there appeared a net elevation in glycemia and lactemia during rapid work to exhaustion. It is concluded that doses of 200-300 mg of caffeine influence the metabolism by augmenting both lipid consumption and the capacity of work to exhaustion. Verf.-Referat