Acute Moderate-Dose β-Alanine Improves Exercise Efficiency via Bicarbonate-Related Mechanisms During a Cycling Time Trial

Background: Research on the acute effects of β-alanine supplementation has primarily focused on performance outcomes, with limited attention to the underlying physiological mechanisms. This study aimed to investigate the acute effects of two β-alanine doses on performance, mechanical output, and acid–base balance during a 10 min cycling time trial (10’-TT), and to explore the relationship between buffering-related variables and performance. Methods: Eighty-five recreational cyclists performed a 10’-TT under indoor conditions before (control) and following the acute ingestion of β-alanine (moderate-dose β-alanine 10 g—BAM; high-dose β-alanine 20 g—BAH) or placebo (PLA), with each condition tested on separate days. Data were analyzed using two-way repeated-measures ANOVA and correlation analyses. Results: No significant differences were observed in performance variables (distance, speed, cadence, or heart rate; p ≥ 0.751). However, total external mechanical work (kJ) was significantly reduced following acute supplementation (p = 0.028). Notably, the BAM condition reduced the mechanical cost of exercise without impairing performance, and this effect was moderately associated with changes in bicarbonate levels. Conclusions: Acute β-alanine supplementation did not improve performance outcomes but may alter buffering-related physiological responses associated with reduced mechanical work during high-intensity cycling exercise. These findings highlight the relevance of buffering-related mechanisms, particularly bicarbonate dynamics, in modulating the mechanical cost (work performed relative to performance achieved) of high-intensity exercise.