Purpose: The purpose of this study was to investigate the effects of 28-days of β-alanine supplementation on four minute cycling time trial performance and to determine if there was an additive effect of combined β-alanine and sodium bicarbonate (NaHCO₃) supplementation on high-intensity cycling performance.

Method: Fourteen highly-trained cyclists (mean ± SD; age = 25.4 ± 7.2 yr; mass = 71.1 ± 7.1 kg; V̇O_2max = 66.6 ± 5.7 mL.kg^-1.min^-1) supplemented for 28-days with β-alanine (65 mg.kg^-1 body mass each day) or placebo. A maximal four minute bout of cycling was performed pre-supplementation (baseline) and twice post-supplementation: following ingestion of NaHCO₃ (300 mg.kg^-1 body mass), and ingestion of a placebo using a randomized crossover design with two days between trials. Blood pH and HCO₃^- concentration were determined pre-loading (post-supplementation trials), pre-test and post-test.

Results: In the acute NaHCO₃ loading trials blood pH and HCO₃^- were elevated from pre-loading to pre-test and the magnitude of the change in HCO₃^- from pre-test to post-test was significantly greater compared to the acute placebo loading trial (P < 0.001). Average power output in the four minute cycling performance trial was increased in placebo + NaHCO₃ (+3.1% ± 1.8%) and β-alanine + NaHCO₃ (+3.3% ± 3.0%) compared to baseline (P < 0.05). β-alanine + placebo did not significantly improve average power output compared to baseline (+1.6% ± 1.7%; P = 0.20), however, magnitude based inferences demonstrated that β-alanine+placebo was associated with a 37% likelihood of producing average power improvements.

Conclusions: In trained cyclists β-alanine supplementation did not significantly improve four minute cycling performance; however, there may be a small meaningful improvement in performance. Acute NaHCO₃ supplementation significantly improved four minute cycling performance. There appeared to be minimal additive effect of combined β-alanine and NaHCO₃ supplementation.