Besides central command, PCO_2art , pH and PO₂ are said to be stimuli of ventilation. It is not known whether these effects are additive during exercise. The aim of this study was to determine the influence of metabolic pH changes on ventilation during high intensity intermittent exercise of a small muscle group. 8 subjects performed handgrip interval exercise under different conditions. The pH was manipulated by ingestion of NH₄Cl (0.07g/kgBW, ACI) or NaHCO₃ (0.2g/kgBW, ALC) in a 90min pre-period (PP), CaCO₃ (0.12g/kgBW, CON) served as control. Blood chemical parameters were analyzed in venous and arterialized blood. Ventilation and muscle power were measured. In PP there was no significant difference in VE, despite significantly different pH_art between the groups (DpH: CON/ACI, CON/ALC: 0.07, p<0.001). The PCO_2art decreased continuously in ACI and increased in ALC (p<0.001). During EP ventilation was not different in the 15sec of exercise itself, but during the 45sec of rest VE differed (p<0.05). This significant increase suggest that the stimuli amplify each other. In the 45 sec of rest during EP, the increase in VE correlated with the decrease in performance (p=0.001, R²=0.32). This relation was independent of pH.