Is Individualization of Sodium Bicarbonate Ingestion Based on Time to Peak Necessary?

Abstract

Purpose: To describe the reliability of blood bicarbonate pharmacokinetics in response to sodium bicarbonate (SB) supplementation across multiple occasions and assess, using putative thresholds, whether individual variation indicated a need for individualised ingestion timings. Methods: Thirteen m en (age 27±5 y; body mass (BM) 77.4±10.5 kg; height 1.75 ±0.06 m) ingested 0.3 g•kg -1 BM SB in gelatine capsules on 3 occasions. One hour after a standardised meal, venous blood was obtained before and every 10 min following ingestion for 3 h, then every 20 min for a further hour. Time-to-peak (Tmax), absolute-peak (Cmax), absolute-peak-change (∆Cmax) and area under the curve (AUC) were analysed using mixed models, intraclass correlation coefficient (ICC), coefficient of variation (CV) and typical error. Individual variation in pharmacokinetic responses was assessed using Bayesian simulation with multilevel models with random intercepts. Results: No significant differences between sessions were shown for blood bicarbonate regarding Cmax, ∆Cmax or AUC (p>0.05), although Tmax occurred earlier in SB2 (127±36 min) than in SB1 (169±54 min, p=0.0088) and SB3 (159±42 min, p=0.05). ICC, CV and typical error showed moderate to poor reliability. Bayesian modelling estimated that >80% of individuals from the population experience elevated blood bicarbonate levels above + 5 mmol•L -1 between 75-240 min after ingestion, and between 90-225 min above +6 mmol•L -1 . Conclusion: Assessing SB supplementation using discrete values showed only moderate reliability at the group level, and poor reliability at the individual level, while Tmax was not reproducible. However, when analysed as modelled curves, a 0.3 g•kg -1 BM dose was shown to create a long-lasting window of ergogenic potential, challenging the notion that SB ingestion individualised to time-topeak is a necessary strategy, at least when SB is ingested in capsules.

The time to peak blood bicarbonate (HCO3−), pH, and strong ion difference (SID) following sodium bicarbonate (NaHCO3) ingestion in highly trained adolescent swimmers

“…On an individual basis, peak HCO 3 − and pH concentrations occurred within 30 min of one another for 11 of 12 participants. The close relationship between these two measurements is synonymous with previous research exploring the dose-response relationship of NaHCO 3 consumed in gelatine capsules [3,22,38]. The remainder of this discussion will therefore focus on HCO 3 − as this measurement typically displays less variance and a greater degree of reliability when compared with pH [2,21].…”

“…Each participant was required to attend the laboratory as per their usual training time (17:00 – 20:30 hrs) having eaten as they normally would prior to a competitive race (i.e., self-selected timing and meal composition). Previous studies have assessed time course changes in HCO 3 − and pH in a fasted state [2,3,36] or following a standardised meal [22], however, these conditions do not replicate the variance in nutritional intakes that would take place in competition. This ingestion method was selected to consider the effects of individualised nutrition on baseline acid-base balance, electrolyte status, and absorption rate that would occur in practice [37].…”

“…Blood samples were obtained and analysed on eight more occasions (60, 75, 90, 105, 120, 135, 150, and 165 min post-NaHCO 3 ingestion) with further samples taken at 180 (n = 4) and 195 min (n = 1) to ensure a peak HCO 3 − was found. No samples were taken within the first 60 min since 0.3 g·kg -1 BM NaHCO 3 in capsule form was not expected to display peak HCO 3 − concentrations in this time [2,22].…”

“…There is an apparent increase in the ergogenic potential of NaHCO 3 when blood HCO 3 − increases above baseline concentrations by 5 mmol·L -1 , whereas increases above 6 mmol·L -1 are associated with almost certain performance enhancement [19,20]. However, the time taken to reach these thresholds varies considerably when NaHCO 3 is consumed in either capsule (range: 40 – 240 min [3,21,22]), or solution form (range: 40 – 125 min [2,23–25]), therefore highlighting a potential flaw in the current dosing guidelines (i.e., 60 – 150 min pre-exercise for all athletes [1]). Contemporary research is addressing this issue by timing exercise to coincide with an individual peak in HCO 3 − concentration [21,23–25], though at present, only Boegman et al [21] has directly compared exercise performance between NaHCO3 ingested at an individual peak in HCO3 − (40 – 160 min pre-exercise) versus a traditionally recommended dosing protocol (60 min pre-exercise for all athletes).…”

“…However, as HCO 3 − was measured at 60 min post-ingestion, and exercise commenced at 90 min post-ingestion, it is possible that further increases in HCO3 − occurred within this 30 min window [2]. Furthermore, HCO3 − was reported at the group level only, leaving it unknown as to whether some adolescents had greater elevations at this time point, or whether large inter-individual variations exist in the time to peak in accordance with adult-like NaHCO 3 absorption [2,3,22]. The purpose of this study was therefore to explore the time course changes and peak blood concentrations of three acid-base balance variables (HCO 3 − , pH, and the SID) in highly trained adolescent athletes following the ingestion of 0.3 g·kg BM -1 NaHCO 3 .…”