Effects of induced metabolic alkalosis on prolonged intermittent-sprint performance

Purpose: Previous studies have shown that induced metabolic alkalosis, via sodium bicarbonate (NaHCO3) ingestion, can improve short-term, repeated-sprint ability. The purpose of this study was to assess the effects of NaHCO3 ingestion on a prolonged, intermittent-sprint test (IST). Methods: Seven female team-sport athletes (mean ± SD: age = 19 ± 1 yr, VO2peak = 45.3 ± 3.1 mL-kg(-1)-min(-1)) volunteered for the study, which had received ethics clearance. The athletes ingested two doses of either 0.2 g-kg(-1) of NaHCO3 or 0.138 g-kg(-1) of NaCI (placebo), in a double-blind, random, counterbalanced order, 90 and 20 min before performing the IST on a cycle ergometer (two 36-min "halves" of repeated ∼ 2-min blocks: all-out 4-s sprint, 100 s of active recovery at 35% VO2peak, and 20 s of rest). Capillary blood samples were drawn from the ear lobe before ingestion, and before, during. and after each half of the IST. VO2 was also recorded at regular intervals throughout the IST. Results: Resting plasma bicarbonate concentration ([HCO3-]) averaged 22.6 ± 0.9 mmol-L-1, and at 90 min postingestion was 21.4 ± 1.5 and 28.9 ± 2.8 mmol-L-1 for the placebo and NaHCO3 conditions, respectively (P < 0.05). Plasma [HCO3-] during the NaHCO3 condition remained significantly higher throughout the IST compared with both placebo and preingestion. There was a trend toward improved total work in the second (P = 0.08), but not first, half of the IST alter the ingestion of NaHCO3. Furthermore, subjects completed significantly more work in 7 of 18 second-half, 4-s sprints after NaHCO3 ingestion. Conclusions: The results of this study suggest that NaHCO3 ingestion can improve intermittent-sprint performance and may be a useful supplement for team-sport athletes.