Abstract des Autors

There is evidence to suggest that muscle fatigue during highly anaerobic exercise is, in part, caused by accumulation of hydrogen ions (H+) within the muscle fibers. This led us to speculate that an increase in blood buffering capacity might enhance H+ removal from the muscle and thereby delay a decrease in muscle pH and improve the performance. The present study was thus undertaken to determine the effects of bicarbonate intake (NaHCO3) on exercise performance, blood pH, and lactate and catecholamine concentrations. Eleven healthy, well-trained male subjects performed two exercises to exhaustion on an ergometric bicycle at a work load of 375 W. Two hours before each test the subjects ingested either a placebo or 0.3 g/kg body weight of NaHCO3. Cycling times to exhaustion were 59.6 and 72.2 sec in placebo and NaHCO3 trials, respectively. Blood pH levels measured immediately after exercise and after a 5 min recovery period were not significantly different between the two conditions. Blood lactate was higher while catecholamine concentrations were lower in NaHC03 than in placebo trials. We conclude that changes in the acid-base status of blood resulting from ingestion of NaHCO3 influence the performance during supramaximal exercise. The higher blood lactate concentration observed in the alkalose condition might be due to a greater lactate production and/or an enhanced efflux of lactate from the muscle. The similar drop in blood pH might be the consequence of the increased buffer potential of extracellular fluids. Finally, the sympathetic response to exercise was found to be reduced by NaHCO3 ingestion. The reasons for this remain unclear. Verf.-Referat