Advanced search
Publication Cover
Research in Sports Medicine
An International Journal
Latest Articles
Submit an article Journal homepage
482
Views
0
CrossRef citations to date
0
Altmetric
Research Article

The blood acid base and gastrointestinal response to three different forms of sodium citrate encapsulation

D. J. Tinniona Department of Sport and Physical Activity, Edge Hill, Ormskirk, UKCorrespondence[email protected]
ORCID Iconhttps://orcid.org/0000-0002-3116-0985View further author information
ORCID Icon,
F.M. Marticorenab Applied Physiology and Nutrition Research Group, University of Sao Paulo, Sao Paulo, BrazilORCID Iconhttps://orcid.org/0000-0002-8712-4975View further author information
ORCID Icon,
B. Dobsona Department of Sport and Physical Activity, Edge Hill, Ormskirk, UKORCID Iconhttps://orcid.org/0000-0003-0413-878XView further author information
ORCID Icon,
N. P. Hiltona Department of Sport and Physical Activity, Edge Hill, Ormskirk, UKORCID Iconhttps://orcid.org/0000-0003-0204-8967View further author information
ORCID Icon,
L. R. Mc Naughtona Department of Sport and Physical Activity, Edge Hill, Ormskirk, UKORCID Iconhttps://orcid.org/0000-0002-3743-3171View further author information
ORCID Icon &
S. A. Sparksa Department of Sport and Physical Activity, Edge Hill, Ormskirk, UKORCID Iconhttps://orcid.org/0000-0003-0910-2225View further author information
ORCID Icon
Received 29 Jul 2022, Accepted 03 Nov 2023, Published online: 28 Nov 2023

ABSTRACT

Enterically coated (ENT) or delayed-release (DEL) capsules may lessen gastrointestinal symptoms (GIS) following acute sodium citrate (SC) ingestion, although the effects on blood acid-base balance are undetermined. Fourteen active males ingested 0.4 g.kg−1 body mass (BM) SC, within gelatine (GEL), DEL and ENT capsules or 0.07 g.kg−1 BM sodium chloride control (CON). Blood acid-base balance and GIS were measured for 4 h. Ingestion form had no significant effect on total GIS experienced (GEL: 2 ± 7; DEL: 1 ± 8; ENT: 1 ± 4 AU). Most (7/14) participants experienced zero symptoms throughout. Peak GIS typically emerged ≤100 min post-ingestion, with a similar time to reach peak GIS between ingestion form (GEL: 36 ± 70; DEL: 13 ± 28; ENT: 15 ± 33 AU). Blood [HCO3−] was significantly higher with ENT versus GEL (ENT: 29.0 ± 0.8; GEL: 28.5 ± 1.1 mmol.L−1, P = 0.037). Acute ingestion of a reduced SC dose elicited minimal GIS, producing significant changes in blood [HCO3−] from rest, irrespective of ingestion form (GEL: 6.0 ± 0.9; DEL: 5.1 ± 1.0; ENT: 6.2 ± 0.8 mmol.L−1). The necessity of individualized ingestion strategies is also challenged, with sustained increases in blood [HCO3−] of ≥4 mmol.L−1 for up to 153 min highlighted. If commencing exercise at peak alkalosis augments subsequent performance above starting at a standardized time point where HCO3− is still elevated remains unclear.

Introduction

High-intensity to endurance-intensive efforts (>6 s to 1+ min) is associated with high levels of glycolytic flux (van Loon et al., Citation2001; Romjin et al., Citation1993), simultaneous to reductions in both muscle and blood pH and [HCO3−] (Fitts, Citation1994). Elevated H+ production versus removal rate may quickly exceed the limits of endogenous HCO3− buffering capacity, contributing to a decline in muscular contractile force and velocity, by interfering with multiple metabolic and contractile processes (Jarvis et al., Citation2018; Sundberg et al., Citation2018; Keyser, Citation2010; Allen, Lamb and Westerblad, Citation2008; Fitts, Citation1994). Exogenously administering extracellular buffers to increase [HCO3−] buffering capacity (Heibel et al., Citation2018) appears a logical method to support pH regulation during such intense efforts.

Theoretically, any increase in circulating [HCO3−] would lead to a corresponding increase in buffering capacity, with sodium citrate (SC) ingestion shown to elevate blood alkalosis when compared to baseline or placebo (Urwin et al., Citation2019). While further investigation is required to elucidate the minimal change in [HCO3−] necessary to induce a performance effect, de Oliveira et al. (Citation2021) recently observed greater effects following increases of 4–6 mmol.L−1 from baseline. The ingestion of the recommended quantities of SC (0.4–0.5 g.kg−1 body mass (BM)) (Cerullo et al., Citation2020; Urwin et al., Citation2021) typically elicits changes in blood [HCO3−] of 5–8 mmol.L−1 (Urwin et al., Citation2019; Russell et al., Citation2014; Vaher et al., Citation2014). These doses are recommended to maximize blood alkalosis, with further increases providing limited additive ergogenic benefit while also increasing the risk of gastrointestinal symptoms (GIS) (McNaughton, Citation1990, 1991; Urwin et al., Citation2019, 2016).

Such large doses of SC are necessary as immediately post-ingestion it rapidly dissociates into Na+ and citrate (Requena et al., Citation2005). Citrate is then removed from the plasma, unbalancing the electrical equilibrium (Devlin, Citation2010). Electrical neutrality is restored by a decrease in [H+] and an increase in [HCO3−], creating the alkalotic response observed post-ingestion (Peacock et al., Citation2021; Urwin et al., Citation2019, Citation2021). At a dose of 0.4 g.kg−1 BM (28 g for a 70 kg individual) blood HCO3− may increase by ~5 mmol ∙ L−1 (Cunha et al., Citation2019), equating to only 17% of the expected increase in HCO3− if the entire dose entered the blood (considering SC should increase [HCO3−] by ~29.6 mmol.L−1 in 5 L of blood). Following identical calculations for sodium bicarbonate (SB), de Oliveira et al. (Citation2018) suggested that the majority of ingested HCO3− is neutralized in gastric acids or may be removed in faeces to a smaller degree. Logically, avoiding such losses of HCO3− would yield larger increases in [HCO3−] and mitigate GIS. An optimal SC ingestion protocol is then one which maximizes blood alkalosis (pH and/or HCO3−) and minimizes the potential of GIS (Cerullo et al., Citation2020 and Urwin et al., Citation2021). This may be addressed by manipulating ingested dose (McNaughton, Citation1990, 1991; Urwin et al., Citation2019, 2016) and/or timing (Gough et al., Citation2017, Citation2018; Miller et al., Citation2016), or more novel approaches such as the use of different delivery modes – capsules rather than solution.

Multiple forms of encapsulation have been trialled with the purpose of avoiding degradation in the stomach, achieved by utilizing the variable pH across the gastrointestinal (GI) tract, meaning degradation of “gastroresistant capsules” occurs primarily in the less acidic duodenum (pH 6–7 arbitrary units [AU]) (Barbosa et al., Citation2017). Gastric acid neutralization is therefore limited, lessening GIS that would otherwise develop alongside elevated CO2 tension in the stomach (Hilton et al., Citation2020).

Hilton et al. (Citation2019) observed reduced incidence/severity of GIS following the administration of delayed-release (DEL) SB, compared to aqueous delivery. Additionally, some individuals have benefitted from augmented bicarbonate bioavailability (≤2 mmol.L−1), supporting the need for ingestion based on individual blood analyte responses. In the sole example, Peacock et al. (Citation2021) recently compared the pharmacokinetic and GIS response to ingesting SB and SC in DEL capsules at an identical dose

(0.3 g.kg−1 BM). While both substances induced significant alkalosis, SB resulted in a greater change in blood [HCO3−]. SC ingestion was also associated with reduced GIS, although at a dose that has yet to consistently demonstrate ergogenicity. Given the value of reduced GIS, there is a demand for future research to understand the minimum effective dose(s) (Peacock et al., Citation2021; Urwin et al., Citation2016).

Hilton et al. (Citation2020) later demonstrated that enterically coated (ENT) capsules have the capacity to further attenuate GIS versus gelatine (GEL) and DEL capsules, providing an additional option for those who experience notable GIS, at an added financial cost. Moreover, changes in blood alkalosis

([HCO3−] and pH) were lower with ENT SB, possibly due to increased absorption across the intestinal mucosa (Turnberg et al., Citation1970) alongside declining absorption time (Hilton et al., Citation2020). Given that the level of induced alkalosis may limit performance effects following both SB and SC (de Oliveira et al., Citation2021), ENT capsules may improve the GIS response at the expense of performance (Hilton et al., Citation2020).

At present, no research has compared the blood acid-base and GIS response to SC ingestion between GEL, DEL or ENT capsules. Successfully minimizing GIS, while understanding the potential implications for performance (i.e., level of blood alkalosis induced) at an apparently ergogenic dose (0.4 g.kg−1 BM) would be of high value to athletes and practitioners. Therefore, the aim of this study was to determine the blood acid-base and GIS responses to the ingestion of 0.4 g.kg−1 BM SC, administered in GEL, DEL and ENT capsules.

Methods

Participants

Fourteen active males (age 27 ± 4, BM 81.4 ± 8.9 kg, peak oxygen uptake 41.43 ± 13.03 mL.kg−1min−1) were recruited for this study. Participants completed regular exercise training (≥3 d . week−1) for at least 2 years and were free of GI-related issues. Exclusion criteria also required that participants were not following a salt-restricted diet or ingesting other buffering agents simultaneous to the current study. All experimental procedures were explained fully, with questions addressed before the provision of written, informed consent. Ethical approval was given by the institutional ethics committee (SPA-REC-2019-252R1).

Experimental overview

In a double-blind, randomized crossover design, participants attended the laboratory on five separate occasions. Following an initial visit (detailed below), experimental trials consisted of a control (CON) and three SC trials, wherein SC was ingested in gelatine (GEL), delayed-release (DEL) or enteric-coated (ENT) capsules. Experimental trials were counterbalanced using block randomization and completed at least 48 h apart to facilitate washout of residual blood HCO3− (Siegler et al., Citation2012). Participants abstained from alcohol or caffeine beverages (El-Sayed et al., Citation2005; Guest et al., Citation2021) for 12 h and strenuous exercise 24 h (Tornero-Aguilera et al., Citation2022) before each trial.

During the initial visit, peak VO2 was determined using a previously outlined protocol (Deb et al., Citation2018), involving 5 min unloaded pedalling (no added resistance) into a ramped increase of 0.5 W ∙ s−1 (30 W . min−1), until volitional exhaustion was reached (Excalibur Sport, Lode, Netherlands). Experimental trials were completed at a similar time-of-day to account for circadian variation (Ayala et al., Citation2021). Participants arrived at the laboratory following an overnight fast. Participants then ingested 0.4 g.kg−1 BM SC in each either GEL, DEL or ENT capsules or the CON (0.07 g.kg−1 BM sodium chloride) (Gough et al., Citation2017) which was administered in size 0 opaque (white) capsules. Capsules were provided in an opaque (black) tub to lessen the visual impact of the large numbers of capsules to be ingested.

All capsules were manually filled by a laboratory technician using a capsule filling device (Capsule Connection LLC, USA) with doses tested for accuracy regularly (Fisher, OHAUSTM). Capsules were consumed with 500 ml of room temperature water (18°C). After ingestion, water was permitted ad libitum with consumption throughout the first trial recorded and replicated as accurately as possible in subsequent trials. Excluding toilet breaks, participants remained seated throughout.

Acid-base balance responses

The response to ingestion was determined based on the time course of blood [HCO3−] and pH changes over a 4 h sampling period. Fingertip capillary blood samples (95 μL) were obtained pre-ingestion and a further 14 times, spread equally over the 238 min window. Samples were collected in heparin-coated capillary tubes (Radiometer Medical Ltd, Denmark) and analysed immediately (Radiometer ABL800 BASIC, Denmark) for blood [HCO3−] and pH. Blood HCO3− measurements were then used to establish the key characteristics of each form of encapsulation, lag time (Tlag), peak blood [HCO3−] (Cmax), change in Cmax (∆Cmax), time-to-reach Cmax (Tmax) and area under the curve (AUC). Bicarbonate Tlag is taken as the point at which blood [HCO3−] increased beyond normal daily fluctuation, established individually following ingestion of CON. Data describing individual responses for both blood HCO3− and pH is also provided.

Gastrointestinal symptoms

At each interval, a GI questionnaire was completed to assess the severity of a range of GI symptoms using a visual analogue scale ([VAS] where 0 = no symptom and 10 = most severe) (Gough et al., Citation2017). Symptoms include nausea, flatulence, stomach cramping, belching, stomach-ache, bowel urgency, diarrhoea, vomiting and stomach belching.

Results

Gastrointestinal symptoms

There was no significant effect of ingestion form on total GIS experienced (F3,39 = 1.316, P = 0.283, ηp2 = 0.092). Total symptoms were also not significantly different in either GEL (6.7 ± 13.2 AU), DEL (4.8 ± 15.7 AU), ENT (1.9 ± 5.3 AU) or CON (0.3 ± 1.1 AU) (F3,36 = 2.359, P = 0.148, ɳp2 = 0.164). Seven of fourteen participants experienced no symptoms irrespective of ingestion form or sample time post-ingestion ().

Table 1. Individual peak GIS reported following different sodium citrate ingestion forms. Symptom scores are displayed in parentheses and are expressed as arbitrary units (AU).

Peak individual GIS typically occurred ≥100 min post-ingestion. Whilst the highest individual symptom occurred earlier following ENT (51 ± 48 min) compared to other ingestion forms (GEL = 102 ± 88 min; DEL 62 ± 20 min), ingestion form had no significant effect on the time-to-reach peak GIS (F2,26 = 1.857, P = 0.176, ɳp2 = 0.125). Only one participant experienced GIS at the point of Tmax in the GEL trial (rated as 1/10 AU only), with no further instances of GIS at Tmax. Furthermore, this participant appeared to display high GIS relative to the remaining sample, based on greater total symptom scores compared to mean values for GEL (7 vs 2 ± 7 AU).

Five of fourteen participants experienced at least one GIS in the GEL trial, whereas only three and four participants experienced GIS following DEL and ENT, respectively. One participant recorded GIS in the CON trial, which occurred around the time of ingestion. Flatulence (24.1%), stomach bloating (20.7%) and bowel urgency (19.0%) represented the most common GIS overall, with diarrhoea (5.3 ± 3.1), vomiting (4 ± 0) and bowel urgency (3.6 ± 1.2) providing the highest severity ratings overall ().

Table 2. Frequency and severity of GIS reported following sodium citrate ingestion (n = 14). The most frequent and severe GIS are highlighted.

Acid-base responses

Ingestion form had a significant effect on blood [HCO3−] (F2,12 = 5.1, P = 0.025, ηp2 = 0.459) but not on pH (F1.6,6.3 = 1.7, P = 0.242, ηp2 = 0.299) and [Na+] (F2,8 = 1.51, P = 0.278, ηp2 = 0.274). Blood [HCO3−] was significantly higher with ENT versus GEL (P = 0.037). In the post-ingestion period, there were significant effects on blood [HCO3−] (F14,84 = 254.72, P < 0.001, ηp2 = 0.977), pH (F2.9,11.6 = 64.521, P < 0.001, ηp2 = 0.942) and [Na+] (F14,56 = 29.026, P = <0.001, ηp2 = 0.879). Blood [HCO3−] and pH were significantly elevated above baseline from 34 to 136 min post-ingestion and remained significantly elevated throughout the remaining sampling period. Blood [Na+] was significantly elevated above baseline from 102- to-170 min post-ingestion. Significant trial × time interactions emerged for blood [HCO3−] (F28,168 = 3.867, P < 0.001, ηp2 = 0.942) and [Na+] (F28,112 = 2.360, P < 0.001, ηp2 = 0.371). There were no significant trial × time interactions for blood pH (F2.64,10.55 = 1.831, P = 0.204, ηp2 = 0.314). Time course responses for blood [HCO3−] and pH are presented in .

Figure 1. Mean (± standard deviation) blood [HCO3-] (a) and pH (b) pre- and post-intgestion of 0.4 gKg−1 body mass sodium citrate, in gelatine (GEL), delayed-release (DEL) and entericcoated (ENT) capsules. The shaded area represents a 4-6 mmol.L−1 increase in blood [HCO3-] relative to basline levels. *Some error bars are omitted for clarity.

Figure 1. Mean (± standard deviation) blood [HCO3-] (a) and pH (b) pre- and post-intgestion of 0.4 gKg−1 body mass sodium citrate, in gelatine (GEL), delayed-release (DEL) and entericcoated (ENT) capsules. The shaded area represents a 4-6 mmol.L−1 increase in blood [HCO3-] relative to basline levels. *Some error bars are omitted for clarity.

After SC ingestion, ∆Cmax was significantly higher in the ENT trial than DEL (P = 0.027), however, values were similar between ENT and GEL (P = 0.794) GEL and DEL (P = 0.112) (6.2 ± 0.8 versus 6.0 ± 0.9 mmol.L−1 and 6.0 ± 0.9 and 5.1 ± 1.0 mmol.L−1, respectively) (). Tmax occurred significantly earlier following GEL compared to ENT (P = 0.023), while Tmax values were otherwise similar between trials. Blood pH peaked at similar time points (P > 0.05) between GEL (153 ± 27 min), DEL (169 ± 42 min) and ENT (179 ± 33 min). Absolute changes in peak blood pH were also similar (P > 0.05) in GEL (0.084 ± 0.018), DEL (0.075 ± 0.032) and ENT (0.084 ± 0.022) trials. Blood HCO3− kinetics for each form of encapsulation are displayed in .

Figure 2. Mean (± SD) (a) and individual (b) changes in blood [HCO3-] following ingestion of different sdium citrate ingrestion forms. *signification greated than PLA (P<0.05).

Figure 2. Mean (± SD) (a) and individual (b) changes in blood [HCO3-] following ingestion of different sdium citrate ingrestion forms. *signification greated than PLA (P<0.05).

Table 3. Within trial variation in bicarbonate kinetic variables for different sodium citrate ingestion forms.

Discussion

This study represents the first investigation to compare the effects of capsule ingestion form on GIS and acid-base responses following individualized SC ingestion. The GIS and blood acid-base responses following the ingestion of SC in ENT capsules were also measured for the first time. Ingestion form had no significant effect on GIS, with GEL, DEL and ENT capsules eliciting similar average total symptom scores and TTP symptoms. Although ∆Cmax was significantly higher following ENT versus DEL capsules, all forms of encapsulation promoted potentially meaningful changes in blood [HCO3−] of 4 + mmol.L−1 in all but two instances (∆Cmax: 3.2 and 3.6 mmol.L−1). This aligns with the work of de Oliveira et al. (Citation2021) who reported evidence of greater effects on exercise performance when ∆Cmax was 4–6 mmol.L−1 versus ≤4 mmol.L−1. Collectively, the necessity of different forms of SC encapsulation is challenged, with limited differences in GIS and blood acid-base kinetics.

Overall SC elicited minor GIS, with low frequency (0.8% of all possible instances) and severity (2.8 ± 1.3 AU) of symptoms reported throughout (). Half (7/14) of all participants reported zero GIS, supporting the notion that GIS following SC ingestion may induce reduced GIS, often discussed relative to SB (Maughan et al., Citation2018). Despite this, Urwin et al. (Citation2022) recently observed no significant difference in GIS severity, reporting similarities in frequency of severe GIS (≥5 AU) of 9–10% of all cases, with 31–37% of all participants reporting one or more severe symptoms. Gastrointestinal symptoms (any score) were reported by 28.6% of all participants herein, which is lower than previous studies (Urwin et al., Citation2019, Citation2021, Citation2022). This may be partly explained by the use of a lower dose in the present study (0.4 compared to 0.5 g.kg−1 BM). Further, direct comparison with GIS reported following the ingestion of SC is difficult, given the use of differing approaches to measuring GIS.

Flatulence, stomach bloating and bowel urgency represented the most common GIS overall, whereas the severity of diarrhoea, vomiting and bowel urgency were notably high. Frequency of symptoms reported did not exceed 1.5% across all capsule forms, with a greatest average severity of 3.3 ± 0.7 AU (). Whilst ENT SC resulted in a lesser average total symptom score (1.9 ± 5.3 AU) relative to DEL capsules (4.8 ± 15.7 AU) which, in turn, elicited fewer total symptoms than GEL capsules (6.7 ± 13.2 AU), these differences were not statistically significant. Interestingly, diarrhoea was not reported following ENT SC only, which may merit further consideration for practical application with athletes who may otherwise avoid supplementation. Mean GIS scores for SC ingested in DEL capsules were higher than previously reported (4.8 ± 15.7 versus 1.5 ± 1.8 AU) (Peacock et al., Citation2021), although a greater quantity was provided herein (0.4 versus 0.3 g.kg−1 BM).

Use of multiple forms of encapsulation have been deployed with the purpose of avoiding degradation in the stomach, potentially lessening GIS that may arise alongside increased stomach CO2 tension (Hilton et al., Citation2020), translating to changes in TTP blood alkalosis and potentially GIS (Hilton et al., Citation2019; Middlebrook et al., Citation2021; Peacock et al., Citation2021). Accordingly, it is unclear why a similar TTP GIS emerged between ingestion forms, typically occurring within 100 min of ingestion and in relative agreement with peak ratings ~60–90 min provided elsewhere (Urwin et al., Citation2021, Citation2022). Furthermore, how the severity of specific GIS may impact performance remains elusive, yet this may clarify why some studies have found GIS symptoms to limit performance (Cameron et al., Citation2010; Deb et al., Citation2018; Saunders et al., Citation2014), whereas others have not (Miller et al., Citation2016; Price & Simons, Citation2010). Future studies may aim to further clarify the relationship between GIS and willingness to commence/continue exercise (Urwin et al., Citation2022). Furthermore, only one participant experienced symptoms at the point of peak blood [HCO3−] (1 AU), suggesting that the peak alkalotic response may emerge somewhat separately to GIS.

Theoretically, any increase in circulating [HCO3−] following the ingestion of SC would lead to a corresponding increase in extracellular buffering capacity (Heibel et al., Citation2018). Whilst the minimal changes necessary to induce ergogenic effects are unclear, data suggest greater effects occurred when blood [HCO3−] increases were moderate (4–6 mmol.L−1) to large (>6 mmol.L−1) (de Oliveira et al., Citation2021). Whether absolute increases at TTP differ substantially from those at standardized time points is unknown. Indeed, the mean increase shown at time-to-peak by Gough et al. (Citation2018) (+6.5 ± 1.3 mmol.L−1) resembles increases shown at 60 min (+6.1 Froio de Araujo Dias et al., Citation2015; +5.1; Jones et al., Citation2016; +5.7; Gough et al., Citation2017), 90 min (+6.5 Jones et al., Citation2016; +6.1; Gough et al., Citation2017) and 120 min (+6.5 Jones et al., Citation2016; +5.6; Gough et al., Citation2017) with a matched 0.3 g.kg−1 BM aqueous dose of SB. Pertinent to the current study, blood HCO3− concentration was similar 60, 120 and 180 min post-ingestion in GEL capsules (Siegler et al., Citation2012).

Post ingestion of SC, ∆Cmax was significantly higher following ENT SC compared to DEL, however ∆Cmax between ingestion forms was otherwise similar (). Across all forms, blood [HCO3−] was significantly elevated above baseline from 34-min post ingestion and throughout the remaining sampling period. Mean data revealed ∆Cmax ≥4 mmol.L−1 after 85–102 min had elapsed, remaining elevated (GEL: +5.3 ± 0.8 mmol.L−1; DEL: +5.0 ± 0.8 mmol.L−1; ENT: +5.5 ± 0.8 mmol.L−1) for up to 153 min (153, 136 and 136 min, respectively) post-ingestion. Notable inter-individual variance was evident for ∆Cmax (GEL: 4.8–7.7; DEL: 3.2–6.7; ENT: 5.2–7.8, mmol.L−1), although ∆Cmax failed to exceed 4 mmol.L−1 on only two occasions, during the DEL trial (3.2 and 3.6 mmol.L−1) ().

Table 4. Individual blood bicarbonate (HCO3−) and pH responses following the ingestion of 0.4 g.kg−1 body mass sodium citrate, in gelatine (GEL), delayed-release (DEL) and enteric-coated (ENT) capsules.

Collectively, it appears that SC in GEL, DEL or ENT capsule form could offer a “window of ergogenicity” that may equate to ~153 min or more, commencing after at least 85 min. Where TTP blood [HCO3−] has been proposed as a method of optimizing the ingestion of buffering agents (Gough et al., Citation2017; Miller et al., Citation2016), it would appear unnecessary given observations here. Contesting this, Boegman et al. (Citation2020) recently demonstrated significant improvements in the rowing performance (200 m time trial) performance of 18/23 world class rowers, utilizing an individualized TTP strategy compared to a standardized approach (367.0 ± 10.5 s vs. = 369.0 ± 10.3 s). Improvements emerged with only a 0.5 mmol.L−1 difference (5.5 versus 6.0 mmol.L−1) in resting HCO3−, suggesting that small changes in HCO3− may induce performance effects, or other mechanisms may be plausible (Newbury et al., Citation2021).

Conclusion

The ingestion of 0.4 g.kg−1 BM SC induces limited GIS, with no significant differences across GEL, DEL or ENT capsules, although minor differences may require practical consideration. While small differences in HCO3− kinetics are highlighted between capsule type, meaningful and sustained changes in blood [HCO3−] beyond potentially ergogenic thresholds were observed across all. Taken together, SC may offer a large(r) “window of ergogenicity” relative to SB, with limited GIS. Although the utility of an individualized approach to SC ingestion remains to be elucidated, the data presented here represent a potential alternative for SC, particularly when determining individual TTP is not possible. Future investigations should seek to translate GIS and blood acid-base responses provided here to exercise contexts, comparing both generalized and individualized approaches.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported that there is no funding associated with the work featured in this article.

References

  • Allen, D. G. Lamb, G. D. & Westerblad, H.(2008). Skeletal muscle fatigue: cellular mechanisms. Physiological Reviews, 88(1), 287–332.
  • Ayala, V., Martínez-Bebia, M., Latorre, J. A., Gimenez-Blasi, N., Jimenez-Casquet, M. J., Conde Pipo, J., Bach-Faig, A., & Mariscal-Arcas, M. (2021). Influence of circadian rhythms on sports performance. Chronobiology International, 38(11), 1522–1536. https://doi.org/10.1080/07420528.2021.1933003
  • Barbosa, J. A., Conway, B. R., & Merchant, H. A. (2017). Going natural: Using polymers from nature for gastroresistant applications. British Journal of Pharmacy, 2(1), 14–30. https://doi.org/10.5920/bjpharm.2017.01
  • Boegman, S., Stellingwerff, T., Shaw, G., Clarke, N., Graham, K., Cross, R., & Siegler, J. C. (2020). The impact of individualizing sodium bicarbonate supplementation strategies on world-class rowing performance. Frontiers in Nutrition, 7, 138. https://doi.org/10.3389/fnut.2020.00138
  • Cameron, S. L., McLay-Cooke, R. T., Brown, R. C., Gray, A. R., & Fairbairn, K. A. (2010). Increased blood pH but not performance with sodium bicarbonate supplementation in elite rugby union players. International Journal of Sport Nutrition and Exercise Metabolism, 20(4), 307–321. https://doi.org/10.1123/ijsnem.20.4.307
  • Cerullo, G., Parimbelli, M., Perna, S., Pecoraro, M., Liguori, G., Negro, M., & D’Antona, G. (2020). Sodium citrate supplementation: An updated revision and practical recommendations on exercise performance, hydration status, and potential risks. Translational Sports Medicine, 3(6), 518–525. https://doi.org/10.1002/tsm2.174
  • Cunha, V. C., Aoki, M. S., Zourdos, M. C., Gomes, R. V., Barbosa, W. P., Massa, M., Moreira, A., & Capitani, C. D. (2019). Sodium citrate supplementation enhances tennis skill performance: A crossover, placebo-controlled, double-blind study. Journal of the International Society of Sports Nutrition, 16(1), 1–8. https://doi.org/10.1186/s12970-019-0297-4
  • Deb, S. K., Gough, L. A., Sparks, S. A., & McNaughton, L. R. (2018). Sodium bicarbonate supplementation improves severe-intensity intermittent exercise under moderate acute hypoxic conditions. European Journal of Applied Physiology, 118(3), 607–615. https://doi.org/10.1007/s00421-018-3801-7
  • de Oliveira, L. F., Dolan, E., Swinton, P. A., Durkalec-Michalski, K., Artioli, G. G., McNaughton, L. R., & Saunders, B. (2021). Extracellular buffering supplements to improve exercise capacity and performance: A comprehensive systematic review and meta-analysis. Sports Medicine, 52(3), 1–22. https://doi.org/10.1007/s40279-021-01575-x
  • de Oliveira, L. F., Saunders, B., & Artioli, G. G. (2018). Is bypassing the stomach a means to optimize sodium bicarbonate supplementation? A case study with a post bariatric surgery individual. International Journal of Sport Nutrition and Exercise Metabolism, 28(6), 660–663. https://doi.org/10.1123/ijsnem.2017-0394
  • Devlin, T. M. (Ed.). (2010). Textbook of biochemistry with clinical correlations. John Wiley & Sons.
  • El-Sayed, M. S., Ali, N., & Ali, Z. E. S. (2005). Interaction between alcohol and exercise. Sports Medicine, 35(3), 257–269. https://doi.org/10.2165/00007256-200535030-00005
  • Fitts, R. H.(1994). Cellular mechanisms of muscle fatigue. Physiological Reviews, 74(1), 49–94.
  • Froio de Araujo Dias, G., da Eira Silva, V., de Salles Painelli, V., Sale, C., Giannini Artioli, G., Gualano, B., Saunders, B., & Earnest, C. P. (2015). (In) consistencies in responses to sodium bicarbonate supplementation: A randomised, repeated measures, counterbalanced and double-blind study. PloS One, 10(11), e0143086. https://doi.org/10.1371/journal.pone.0143086
  • Gough, L. A., Deb, S. K., Sparks, A. S., & McNaughton, L. R. (2017). The reproducibility of blood acid base responses in male collegiate athletes following individualised doses of sodium bicarbonate: A randomised controlled crossover study. Sports Medicine, 47(10), 2117–2127. https://doi.org/10.1007/s40279-017-0699-x
  • Gough, L. A., Deb, S. K., Sparks, S. A., & McNaughton, L. R. (2018). Sodium bicarbonate improves 4 km time trial cycling performance when individualised to time to peak blood bicarbonate in trained male cyclists. Journal of Sports Sciences, 36(15), 1705–1712. https://doi.org/10.1080/02640414.2017.1410875
  • Guest, N. S., Van Dusseldorp, T. A., Nelson, M. T., Grgic, J., Schoenfeld, B. J., Jenkins, N. D., Arent, S. M., Antonio, J., Stout, J. R., Trexler, E. T., Smith-Ryan, A. E., Goldstein, E. R., Kalman, D. S., & Campbell, B. I. (2021). International society of sports nutrition position stand: Caffeine and exercise performance. Journal of the International Society of Sports Nutrition, 18(1), 1–37. https://doi.org/10.1186/s12970-020-00383-4
  • Heibel, A. B., Perim, P. H., Oliveira, L. F., McNaughton, L. R., & Saunders, B. (2018). Time to optimize supplementation: Modifying factors influencing the individual responses to extracellular buffering agents. Frontiers in Nutrition, 5(35), 1–12. https://doi.org/10.3389/fnut.2018.00035
  • Hilton, N. P., Leach, N. K., Craig, M. M., Sparks, S. A., & McNaughton, L. R. (2020). Enteric-coated sodium bicarbonate attenuates gastrointestinal side-effects. International Journal of Sport Nutrition and Exercise Metabolism, 30(1), 62–68. https://doi.org/10.1123/ijsnem.2019-0151
  • Hilton, N. P., Leach, N. K., Sparks, S. A., Gough, L. A., Craig, M. M., Deb, S. K., & McNaughton, L. R. (2019). A novel ingestion strategy for sodium bicarbonate supplementation in a delayed-release form: A randomised crossover study in trained males. Sports Medicine-Open, 5(1), 1–8. https://doi.org/10.1186/s40798-019-0177-0
  • Jarvis, K. Woodward, M. Debold, E. P. & Walcott, S.(2018). Acidosis affects muscle contraction by slowing the rates myosin attaches to and detaches from actin. Journal of Muscle Research and Cell Motility, 39, 135–147.
  • Jones, R. L., Stellingwerff, T., Artioli, G. G., Saunders, B., Cooper, S., & Sale, C. (2016). Dose-response of sodium bicarbonate ingestion highlights individuality in time course of blood analyte responses. International Journal of Sport Nutrition and Exercise Metabolism, 26(5), 445–453–0286. https://doi.org/10.1123/ijsnem.2015-0286
  • Keyser, R. E.(2010). Peripheral fatigue: High-energy phosphates and hydrogen ions. Pm&r, 2(5), 347–358.
  • Maughan, R. J., Burke, L. M., Dvorak, J., Larson-Meyer, D. E., Peeling, P., Phillips, S. M., Rawson, E. S., Walsh, N. P., Garthe, I., Geyer, H., Meeusen, R., van Loon, L., Shirreffs, S. M., Spriet, L. L., Stuart, M., Vernec, A., Currell, K., Ali, V. M. … Erdener, U. (2018). IOC consensus statement: Dietary supplements and the high-performance athlete. International Journal of Sport Nutrition and Exercise Metabolism, 28(2), 104–125. https://doi.org/10.1123/ijsnem.2018-0020
  • McNaughton, L. R. (1990). Sodium citrate and anaerobic performance: Implications of dosage. European Journal of Applied Physiology and Occupational Physiology, 61(5), 392–397. https://doi.org/10.1007/BF00236058
  • Middlebrook, I., Peacock, J., Tinnion, D. J., Leach, N. K., Hilton, N. P., Saunders, B., Sparks, S. A., & McNaughton, L. R. (2021). Capsule size alters the timing of metabolic alkalosis following sodium bicarbonate supplementation. Frontiers in Nutrition, 8, 634465. https://doi.org/10.3389/fnut.2021.634465
  • Miller, P., Robinson, A. L., Sparks, S. A., Bridge, C. A., Bentley, D. J., & McNaughton, L. R. (2016). The effects of novel ingestion of sodium bicarbonate on repeated sprint ability. The Journal of Strength & Conditioning Research, 30(2), 561–568. https://doi.org/10.1519/JSC.0000000000001126
  • Newbury, J. W., Cole, M., Kelly, A. L., Chessor, R. J., Sparks, S. A., McNaughton, L. R., Gough, L. A., & Sunderland, C. (2021). The time to peak blood bicarbonate (HCO3–), pH, and the strong ion difference (SID) following sodium bicarbonate (NaHCO3) ingestion in highly trained adolescent swimmers. PLoS One, 16(7), e0248456. https://doi.org/10.1371/journal.pone.0248456
  • Peacock, J., Sparks, S. A., Middlebrook, I., Hilton, N. P., Tinnion, D., Leach, N., Saunders, B., & McNaughton, L. R. (2021). Extracellular buffer choice influences acid-base responses and gastrointestinal symptoms. Research in Sports Medicine, 29(6), 505–516. https://doi.org/10.1080/15438627.2021.1896517
  • Price, M. J., & Simons, C. (2010). The effect of sodium bicarbonate ingestion on high-intensity intermittent running and subsequent performance. The Journal of Strength & Conditioning Research, 24(7), 1834–1842. https://doi.org/10.1519/JSC.0b013e3181e06e4a
  • Requena, B., Zabala, M., Padial, P., & Feriche, B. (2005). Sodium bicarbonate and sodium citrate: Ergogenic aids? The Journal of Strength & Conditioning Research, 19(1), 213–224.10.1519/13733.1. https://doi.org/10.1519/00124278-200502000-00036
  • Romijn, J. A. Coyle, E. F. Sidossis, L. S. Gastaldelli, A. Horowitz, J. F. Endert, E. & Wolfe, R. R.(1993). Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration. American Journal of Physiology-Endocrinology & Metabolism, 265(3), E380–E391.
  • Russell, C. Papadopoulos, E. Mezil, Y. Wells, G. D. Plyley, M. J. Greenway, M. & Klentrou, P.(2014). Acute versus chronic supplementation of sodium citrate on 200 m performance in adolescent swimmers. Journal of the International Society of Sports Nutrition, 11(1), 26.
  • Saunders, B., Sale, C., Harris, R. C., & Sunderland, C. (2014). Sodium bicarbonate and high-intensity-cycling capacity: Variability in responses. International Journal of Sports Physiology & Performance, 9(4), 627–632. JSPP.2013-0295 https://doi.org/10.1123/ijspp.2013-0295
  • Siegler, J. C., Marshall, P. W., Bray, J., & Towlson, C. (2012). Sodium bicarbonate supplementation and ingestion timing: Does it matter? The Journal of Strength & Conditioning Research, 26(7), 1953–1958. https://doi.org/10.1519/JSC.0b013e3182392960
  • Sundberg, C. W. Hunter, S. K. Trappe, S. W. Smith, C. S. & Fitts, R. H.(2018). Effects of elevated H+ and pi on the contractile mechanics of skeletal muscle fibres from young and old men: Implications for muscle fatigue in humans. Journal of Physiology, Paris, 596(17), 3993–4015.
  • Tornero-Aguilera, J. F., Jimenez-Morcillo, J., Rubio-Zarapuz, A., & Clemente-Suárez, V. J. (2022). Central and peripheral fatigue in physical exercise explained: A narrative review. International Journal of Environmental Research and Public Health, 19(7), 3909. https://doi.org/10.3390/ijerph19073909
  • Turnberg, L. A., Fordtran, J. S., Carter, N. W., & Rector, F. C. (1970). Mechanism of bicarbonate absorption and its relationship to sodium transport in the human jejunum. The Journal of Clinical Investigation, 49(3), 548–556. https://doi.org/10.1172/jci106265
  • Urwin, C. S. Dwyer, D. B. & Carr, A. J.(2016). Induced alkalosis and gastrointestinal symptoms after sodium citrate ingestion: A dose-response investigation. International Journal of Sport Nutrition and Exercise Metabolism, 26(6), 542–548.
  • Urwin, C. S., Snow, R. J., Condo, D., Snipe, R., Wadley, G. D., & Carr, A. J. (2021). Factors influencing blood alkalosis and other physiological responses, gastrointestinal symptoms, and exercise performance following sodium citrate supplementation: A review. International Journal of Sport Nutrition and Exercise Metabolism, 31(2), 168–186. https://doi.org/10.1123/ijsnem.2020-0192
  • Urwin, C. S., Snow, R. J., Condo, D., Snipe, R. M., Wadley, G. D., Convit, L., & Carr, A. J. (2022). A comparison of sodium citrate and sodium bicarbonate ingestion: Blood alkalosis and gastrointestinal symptoms. International Journal of Sport Nutrition and Exercise Metabolism, 33(1), 1–10. https://doi.org/10.1123/ijsnem.2022-0083
  • Urwin, C. S., Snow, R. J., Orellana, L., Condo, D., Wadley, G. D., & Carr, A. J. (2019). Sodium citrate ingestion protocol impacts induced alkalosis, gastrointestinal symptoms, and palatability. Physiological Reports, 7(19), e14216. https://doi.org/10.14814/phy2.14216
  • Urwin, C. S., Snow, R. J., Orellana, L., Condo, D., Wadley, G. D., Carr, A. J., & McNaughton, L. (2021). Does varying the ingestion period of sodium citrate influence blood alkalosis and gastrointestinal symptoms? PloS One, 16(5), e0251808. https://doi.org/10.1371/journal.pone.0251808
  • Vaher, I. Timpmann, S. Aedma, M. & Ööpik, V.(2015). Impact of acute sodium citrate ingestion on endurance running performance in a warm environment. European Journal of Applied Physiology, 115, 813–823.
  • Van Loon, L. J. Greenhaff, P. L. Constantin‐Teodosiu, D. Saris, W. H. & Wagenmakers, A. J.(2001). The effects of increasing exercise intensity on muscle fuel utilisation in humans. Journal of Physiology, Paris, 536(1), 295–304.
Download PDF

Related research

People also read lists articles that other readers of this article have read.

Recommended articles lists articles that we recommend and is powered by our AI driven recommendation engine.

Cited by lists all citing articles based on Crossref citations.
Articles with the Crossref icon will open in a new tab.