Author(s): YANG, X.1, HE, Z.2, YANG, Q.1, MCNAUGHTON, L.3, Institution: BEIJING SPORT UNIVERSITY, Country: CHINA, Abstract-ID: 962

INTRODUCTION:
Sodium bicarbonate (SB) supplementation enhances extracellular buffering and high-intensity exercise performance. But the effects of different SB doses and ingestion strategies on restoring alkalosis and sustaining performance during repeated maximal exercise remain unclear. Evidence is limited on how SB-induced alkalosis affects critical power (CP) and the finite work capacity above CP (W′) in repeated high-intensity bouts. This study aims to compare four SB strategies, varying in dose and ingestion frequency, on CP, W′, and blood alkalosis during two 3-min all-out cycling tests separated by 70 min.
METHODS:
Seventeen trained males (age: 20.8 ± 2.0 yr; height: 180.6 ± 5.5 cm; body mass: 76.0 ± 6.0 kg; V̇O₂peak: 55.1 ± 3.9 mL·kg⁻¹·min⁻¹) completed a randomized crossover study. Participants ingested SB at 0.3 g·kg⁻¹ or 0.4 g·kg⁻¹, or an sodium chloride placebo (PLA) in gelatin capsules. Strategies included: single 0.3 g·kg⁻¹ (SM-SB), multiple progressive 0.3 g·kg⁻¹ (MM-SB), single 0.4 g·kg⁻¹ (SH-SB), multiple progressive 0.4 g·kg⁻¹ (MH-SB), and PLA. Ninety minutes after supplementation, participants performed two 3-min all-out cycling tests (3MT1, 3MT2) separated by 70 min. CP and W′ were derived from each test. Blood HCO₃⁻ was assessed at baseline, pre-3MT1, immediately, 20, 40, and 60 min post-3MT1, pre-3MT2 (70 min post-3MT1), and immediately post-3MT2. Linear mixed-effects models examined the effects of supplementation strategy and time, with strategy and time as fixed effects, participant as a random effect. Statistical significance was set at P < 0.05.
RESULTS:
No interaction effects between supplementation strategy and time were observed for CP or W′. W′ was lower during 3MT2 than 3MT1 (F = 4.57, P <0.05). A main effect of supplementation strategy was observed for overall W′ (F = 4.79, P <0.05). Compared with PLA, W′1 was higher following SM-SB (t = 2.85, P <0.05), SH-SB (t = 2.43, P <0.05), and MH-SB (t = 2.32, P <0.05), with no differences among these strategies. Only SH-SB maintained higher W′ during 3MT2 (t = 2.74, P <0.05). CP was unaffected by strategy but differed between CP1 and CP2 (F = 12.09, P <0.05). A significant strategy × time interaction was observed for HCO₃⁻ (F = 2.07, P <0.05). All SB strategies elevated HCO₃⁻ relative to PLA before both 3MTs and immediately post-3MT1 (P <0.05). In PLA, HCO₃⁻ returned to baseline only after 70 min post-3MT1, whereas all SB strategies returned within 40 min and exceeded baseline at 60 min (P <0.05), though remaining below pre-3MT1 peaks at 70 min. No differences in HCO₃⁻ were observed among SB strategies that enhanced W′.
CONCLUSION:
Standardized SB strategies enhanced extracellular buffering and W′ without affecting CP. A single acute dose of 0.3 g·kg⁻¹ improved W′, while progressive ingestion at the same dose did not. At 0.4 g·kg⁻¹, both single acute and progressive ingestion increased alkalosis and W′, but only a single acute 0.4 g·kg⁻¹ maintained enhanced W′ across two high-intensity bouts separated by 70 min.