Nielsen et al. (2001) found a benefit of acidification on force and muscle excitability depressed by high [K⁺]_o in vitro. In contrast, Kristensen et al. (2005) found no effect of acidification on force in stimulated muscle. The aim of this study was to determine the influence of metabolic pH changes on performance and m-wave during intermittent exercise of high intensity of a small muscle group. 8 subjects performed handgrip interval exercise at maximum power. pH was manipulated by ingestion of NH₄Cl (0.07g/kg BW, ACI) or NaHCO₃ (0.2g/kg BW, ALC) in a 90 min pre-period (PP), CaCO₃ (0.12g/kg BW, CON) served as control. Blood chemical parameters were analyzed in venous and arterialized blood. Mechanical parameters were measured and m-wave was recorded by surface electrodes. Before the exercise period (EP) the pH_art differed significantly by 0.07 between ACI/CON and ALC/CON, respectively (p<0.001). We found no differences in m-wave area in PP, but in EP it was significantly lower in ACI (p<0.05). Time to maximum was significantly lower in CON (p<0.001). The [K⁺]_art/ven in PP and EP and the [K⁺]release in PP were significantly different (ACI>CON>ALC; p<0.05), this might be explained by a different activity of the Na⁺/K⁺-pump. Nevertheless, performance was not affected by pH-disturbances.