Abstract des Autors

It has recently been demonstrated that ventilation (VE) was increased during exercise after glycogen depletion, in spite of a marked increase in plasma pH (pHp). In the present experiments, six endurance trained men performed two successive cyclo-ergometric incremental exercise tests (tests A, B) after normal nutrition (N) and after a fatty meal in conjunction with a sodium bicarbonate (NaHCO3) solution (FSB) or without NaHCO3 (F), and the relationship between VE, plasma potassium concentration (<K+>p), and pHp was checked. Plasma free fatty acid concentration (<FFA>p) was markedly increased in the F and FSB trials. In FSB pHp was significantly increased, compared to N and F. In all the B tests, pHp increased during moderate and intense exercise and in FSB, remained alkalotic even during maximal exercise intensity. In contrast, VE and <K+>p changes were almost equal in all the trials and in tests A and B. It was found that exercise-induced changes of VE and <K+>p in the present experiments were not markedly affected by <FFA>p or pHp values and that these changes also occurred independently of changes in pHp or plasma bicarbonate concentration. The often used glycogen depletion strategy may have slightly increased VE but apparently did not overcompensate for a possible decrease in VE due to increased pHp. The close relationship between VE and <K+>p was not affected by acid-base or substrate changes; this would further confirm the hypothesis that K+ may act as a stimulus for exercise VE.