Six weight trained males were studied prior to, during, and in recovery from exhaustive resistance exercise, 105 min after ingesting 300 mg.kg-1 of either a placebo or NaHCO3. The exercise test consisted of four sets of 12 repetitions with a fifth set to volitional fatigue on a Universal leg press machine at a resistance equaling approximately 70% of the subjects 1-repetition maximum. Arterialized venous blood was analyzed for lactate concentration, blood gas, and acid-base parameters. The ingestion of NaHCO3 produced a significant increase in resting pH (7.39 to 7.46), HCO3- (22.9 to 28.3 mEq.l-1), and oxygenated base excess (-1.3 to 4.4 mEq.l-1). With the completion of each exercise set, a progressive decline in the acid-base status of both groups was observed (pH set 1-5: NaHCO3, 7.40 to 7.31; placebo, 7.34 to 7.25; HCO3- set 1-5: NaHCO3, 25.3 to 17.9; placebo, 21.7 to 15.3 mEq.l-1; base excess set 1-5: NaHCO3, 3.7 to -7.1; placebo, -1.4 to -10.7 mEq.l-1); however, the NaHCO3 condition was significantly more alkaline than the placebo condition. Blood lactate concentration [La] progressively increased with the completion of each exercise set ([La] set 1-5: NaHCO3, 1.37 to 11.15; placebo, 1.31 to 9.81 mM); but were not significantly different between treatments. Repetitions performed in the final exercise set were not significantly different between groups (NaHCO3: 19.6 +/- 1.6, placebo: 18.2 +/- 1.1 repetitions).(ABSTRACT TRUNCATED AT 250 WORDS)