Effect of induced alkalosis on exhaustive leg press performance

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Fifteen males were studied before, during, and in recovery from exhaustive resistance exercise 105 min after ingesting 0.3 g·kg-1 of either a placebo (white flour) or sodium bicarbonate (NaHCO3).


The exercise consisted of five maximal sets on a leg press machine. The load was adjusted to maintain the number of repetitions per set for each subject at approximately 12 repetitions. A significant (P < 0.05) increase in pH (7.40 to 7.47), oxygenated base excess (OxyBE) (-1.3 to 4.0 mEq·L-1), and bicarbonate concentration ([HCO3-])(22.8 to 27.4 mM) was achieved before exercise with the ingestion of NaHCO3.


The exercise protocol produced significant changes in acid base status consistent with metabolic acidosis for both trials (pH sets 1-5: placebo, 7.4 to 7.26; NaHCO3, 7.47 to 7.33), (OxyBE sets 1-5: placebo, -1.3 to -12.3 mEq·L-1; NaHCO3, 4.0 to -6.9 mEq·L-1) and([HCO3-] sets 1-5: placebo, 22.9 to 14.0 mM; NaHCO3, 27.4 to 17.6 mM). After every set; pH, OxyBE, and [HCO3-] were significantly higher in the NaHCO3 trial. Blood lactate concentration([La-]) significantly increased throughout exercise for both trials([La-] sets 1-5: placebo, 4.6 to 11.3 mM; NaHCO3, 4.8 to 13.4 mM). After sets 4 and 5, blood [La-] was significantly higher in the NaHCO3 trial. Bicarbonate ingestion did not improve performance (total repetitions: NaHCO3 = 59 ± 3; placebo = 60 ± 2).


This may be a result of a lower demand on the whole body metabolic system in comparison with that for other modes of exercise in which ergogenic effects have been found.

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