β-Alanine Plus Sodium Bicarbonate Co-Supplementation Does Not Decrease Neuromuscular Fatigue in Swimming.

This study aimed to investigate the effects of chronic β-alanine (βA) plus acute sodium bicarbonate (SB) co-supplementation on neuromuscular fatigue during high-intensity intermittent efforts in swimming. Eleven regional and national competitive-level young swimmers performed a neuromuscular fatigue assessment before and immediately after two 20 × 25-m front crawl maximal efforts every 90 s, performed at pre- and post-4-week co-supplementation. Neuromuscular fatigue was evaluated by percutaneous electrical stimuli through the twitch interpolation technique on the and . Performance was defined by the mean time of the 20 efforts and blood samples to lactate concentrations were collected every four efforts. Participants supplemented 3.2-6.4 g·day of chronic βA or placebo (PL) during four weeks, and acute 0.3 g·kg of SB or PL 60 min before the second assessment (allowing βA+SB and PL+PL groups). No statistical changes were found in neuromuscular fatigue of . In the , a main effect of time was found in potentiated twitch delta values in pooled groups, showing a statistical increase of 19.01% after four weeks (Δ = 13.05 [0.35-25.75] N; = 0.044), without time × group interactions. No statistical difference was found in the swimming performance. Blood lactate increased by 25.06% only in the βA+SB group (Δ = 6.40 [4.62-8.18] mM; < 0.001) after the supplementation period. In conclusion, 4-week βA and SB co-supplementation were not able to reduce neuromuscular fatigue levels and improve performance in highintensity intermittent efforts, but statistically increased blood lactate levels.