Effects of post-exercise sodium bicarbonate ingestion on acid-base balance recovery and time-to-exhaustion running performance: a randomised crossover trial in recreational athletes

Abstract

This study investigated the effect of post-exercise sodium bicarbonate (NaHCO ₃) ingestion on acid-base balance recovery and time-to-exhaustion (TTE) running performance. Eleven male runners (stature, 1.80 ± 0.05 m; body mass, 74.4 ± 6.5 kg; maximal oxygen consumption, 51.7 ± 5.4 mL·kg ⁻¹·min ⁻¹) participated in this randomised, single-blind, counterbalanced and crossover design study. Maximal running velocity (v-V̇O _2max) was identified from a graded exercise test. During experimental trials, participants repeated 100% v-V̇O _2max TTE protocols (TTE1, TTE2) separated by 40 min following the ingestion of either 0.3 g·kg ⁻¹ body mass NaHCO ₃ (SB) or 0.03 g·kg ⁻¹ body mass sodium chloride (PLA) at the start of TTE1 recovery. Acid-base balance (blood pH and bicarbonate, HCO ₃ ^–) data were studied at baseline, post-TTE1, after 35 min recovery and post-TTE2. Blood pH and HCO ₃ ^– concentration were unchanged at 35 min recovery (p > 0.05), but HCO ₃ ^– concentration was elevated post-TTE2 for SB vs. PLA (+2.6 mmol·L ⁻¹; p = 0.005; g = 0.99). No significant differences were observed for TTE2 performance (p > 0.05), although a moderate effect size was present for SB vs. PLA (+14.3 s; g = 0.56). Post-exercise NaHCO ₃ ingestion is not an effective strategy for accelerating the restoration of acid-base balance or improving subsequent TTE performance when limited recovery is available.

Novelty: Post-exercise sodium bicarbonate ingestion did not accelerate the restoration of blood pH or bicarbonate after 35 min. Performance enhancing effects of sodium bicarbonate ingestion may display a high degree of inter-individual variation. Small-to-moderate changes in performance were likely due to greater up-regulation of glycolytic activation during exercise.