Effects of β-alanine and sodium bicarbonate supplementation on the estimated energy system contribution during high-intensity intermittent exercise

Abstract

The effects of β-alanine (BA) and sodium bicarbonate (SB) on energy metabolism during work-matched high-intensity exercise and cycling time-trial performance were examined in 71 male cyclists. They were randomised to receive BA + placebo (BA, n = 18), placebo + SB (SB, n = 17), BA + SB (BASB, n = 19), or placebo + placebo (PLA, n = 18). BA was supplemented for 28 days (6.4 g day) and SB (0.3 g kg) ingested 60 min before exercise on the post-supplementation trial. Dextrose and calcium carbonate were placebos for BA and SB, respectively. Before (PRE) and after (POST) supplementation, participants performed a high-intensity intermittent cycling test (HICT-110%) consisting of four 60-s bouts at 110% of their maximal power output (60-s rest between bouts). The estimated contribution of the energy systems was calculated for each bout in 39 of the participants (BA: n = 9; SB: n = 10; BASB: n = 10, PLA: n = 10). Ten minutes after HICT-110%, cycling performance was determined in a 30-kJ time-trial test in all participants. Both groups receiving SB increased estimated glycolytic contribution in the overall HICT-110%, which approached significance (SB: + 23%, p = 0.068 vs. PRE; BASB: + 18%, p = 0.059 vs. PRE). No effects of supplementation were observed for the estimated oxidative and ATP-PCr systems. Time to complete 30 kJ was not significantly changed by any of the treatments, although a trend toward significance was shown in the BASB group (p = 0.06). We conclude that SB, but not BA, increases the estimated glycolytic contribution to high-intensity intermittent exercise when total work done is controlled and that BA and SB, either alone or in combination, do not improve short-duration cycling time-trial performance.

Sodium Bicarbonate Ingestion Improves Time-to-Exhaustion Cycling Performance and Alters Estimated Energy System Contribution: A Dose-Response Investigation

“…Moderate, albeit non-significant, increases were observed for W [LA] during the HICT without altering energy demand or contribution from W AER , which is in agreement to findings from recent studies (20,21,31). Despite not achieving statistical significance, these increases were considered substantial for both SBC2 (+15.8%) and SBC3 (+30.3%) when compared to PLA, with the relatively small absolute changes in W [LA] attributed to the controlled total mechanical work during the HICT (20). The most novel finding, however, was that there may be a dose-response effect of NaHCO 3 ingestion on changes in energy system contributions, with a small effect size present for W [LA] in favor of SBC3.…”

“…Considering that enhanced buffering capacity is responsible for elevating glycolytic contribution, one explanation for these dose-dependent results could relate to the total amount of H + that can be neutralized. Assuming that total blood volume is ~5 L and that [ ] was as small as ~1.0 mmol.l −1 higher for SBC3 vs. SBC2, then the higher dose could have allowed the neutralization of an extra ~5 mmoles of H + (based on the 1:1 stoichiometry of and H + reaction), in theory eliciting a greater up-regulation of glycolytic contribution ( 20 ). It is important to note, however, that as the current methodology only indirectly assesses glycolytic flux (i.e., from changes in [BLa − ]), these increases in W [LA] contribution may overestimate glycolytic activation, instead reflecting greater lactate efflux from working muscles ( 5 ).…”

“…This approach has recently been shown to provide reliable and valid estimations for W AER during intermittent exercise ( 20 , 29 ). The glycolytic pathway (W [LA] ) was calculated from the assumption that a difference of 1 mmol.l −1 of BLa − obtained by subtracting baseline [BLa − ] from peak [BLa − ] (i.e., delta [BLa − ]) corresponded to 3 ml.kg −1 BM of O 2 ( 20 , 29 – 32 ). Therefore, delta [BLa − ] for each of the three 60 s bouts and during TTE cycling (i.e., difference from pre to post) was multiplied by 3 and the participants' body mass to calculate W [LA] .…”

“…The ergogenic benefits associated with NaHCO 3 ingestion are somewhat related to the increased activation of glycolytic energy pathways (20,21). Whilst this is debated (22), NaHCO 3 ingestion attenuates muscle acidosis during exercise thus preventing the allosteric inhibition of glycogen phosphorlyase and phosphofructokinase (5).…”

“…Whilst this is debated (22), NaHCO 3 ingestion attenuates muscle acidosis during exercise thus preventing the allosteric inhibition of glycogen phosphorlyase and phosphofructokinase (5). This has been shown to increase estimated glycolytic contribution during HIIT protocols (20), while there is robust evidence suggesting enhanced glycolytic flux within the muscle (23). Strategies that elevate glycolytic energy system contribution may enhance exercise capacity during HIIT, however, research is yet to determine whether smaller NaHCO 3 doses elicit a similar physiological response.…”