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

Abstract

BACKGROUND: Research on the acute effects of ?-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 ?-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 ?-alanine (moderate-dose ?-alanine 10 g-BAM; high-dose ?-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 ?-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.