Effects of a sodium bicarbonate hydrogel supplement on gastrointestinal symptoms and performance during high-intensity running

Abstract Background The effects of a sodium bicarbonate hydrogel supplement (SBH) on gastrointestinal (GI) symptoms and running performance were examined. Methods Fifteen recreational runners completed three randomly counterbalanced trials, in which they consumed a placebo (PL), sodium bicarbonate capsules (SB; 0.3 g/kgBM) or SBH (0.3 g/kgBM) 90 min prior to exercise. Trials consisted of 20 intervals of 25 s at 100% VO 2max and an 800 m time-trial. Blood lactate was recorded prior to exercise, following the intervals and after the time-trial. Nine GI symptoms were assessed before supplementation, 90 min post-supplementation, and following the sprints and time-trial. ANOVAs were performed to assess within-subject treatment effects on blood lactate, glucose, and time-trial performance. Wilcoxon Signed Ranks tests were used to determine treatment effects on GI symptoms. Results Lactate responses were similar between SB and SBH, with both treatments eliciting higher peak lactate levels (post 800 m: 6.7 ± 1.8; 6.6 ± 1.4 mmol/L, respectively) versus PL (4.9 ± 1.6 mmol; p < 0.05). GI symptom scores with SB were elevated post-supplementation and at multiple exercise timepoints versus pre-supplementation levels (9.9 ± 1.3); peak GI symptoms with SB (14.7 ± 6.7) were significantly higher than PL (11.2 ± 2.7). By contrast, GI symptoms with SBH did not increase significantly versus pre-supplementation (10.3 ± 1.5), and peak values (11.4 ± 3.8) were not different from PL. GI symptoms summed across all post-supplementation timepoints were higher in SB (52.6 ± 18.1) versus PL (42.3 ± 6.8), with no differences between PL and SBH (45.3 ± 10.8). No differences in 800-m times were observed between PL (195.2 ± 39.2 s), SB (199.2 ± 50.0 s), and SBH (194.3 ± 43.8 s). Conclusions Blood lactate responses were similar between SB and SBH, presumably indicating similar efflux rates of lactate and hydrogen ions from muscle. GI symptom scores increased significantly with SB (versus PL), but not with SBH. However, no differences in performance were observed between SBH and SB treatments and neither improved performance versus PL, perhaps due to relatively modest changes in peak lactate and GI symptoms elicited by this exercise protocol.