Ten male subjects underwent exercise testing in three modes, arms (A), legs (L), and arms + legs (A + L), after ingesting 0.3 g·kg-1body weight of either NaHCO3to induce alkalosis or CaCO3 as a placebo (i.e, six exercise trials). Ratings of perceived exertion (RPE: Borg, 15-pt scale) for the arms (RPE-A), legs (RPE-L), chest (REP-C), and overall body (RPE-O) did not differ between acid-base conditions at 20, 40, or 60% &OV0312;O2maxfor all three exercise modes. At 80% &OV0312;O2max, 1) RPE-A was lower (P< 0.01) during A; 2) RPE-L was lower (P< 0.01) during L; and 3) RPE-A and RPE-L were lower (P< 0.01) during A + L under the NaHCO3as compared to the CaCO3condition. Differences were not found for RPE-L during A or for RPE-A during L. RPE-C and RPE-O were lower (P< 0.01) under NaHCO3during A, L, and A + L. Blood acid-base, &OV0312;O2, and cardiorespiratory responses were not differentially influenced by exercise mode. Blood pH was significantly higher under NaHCO3than CaCO3at pre-exercise and 80% &OV0312;o2max, &OV0312;o2, heart rate, and tidal volume did not differ between acid-base conditions at any exercise intensity. &OV0312;Eand respiratory rate did not differ between acid-base conditions at 20,40, or 60% &OV0312;o2maxbut were significantly lower under NaHCO3at 80% &OV0312;o2max. RPE-A and L were positively related to blood [H+], and RPE-C was positively related to &OV0312;Efor all exercise modes.