Sodium citrate (SC) has been the subject of a relatively large quantity of research over the last 30+ years, centred around its potential as an extracellular buffering agent, which remains unclear at present. The lack of a clear performance benefit following SC use may be partly explained by inefficacious ingestion practices, whereby an ineffective dosage was provided, timing of ingestion pre-exercise was not fully considered and/or other contributing elements of the protocol were overlooked, i.e., ingestion form. To date, a protocol which simultaneously manages many of these elements has not been applied to an exercise scenario. Based on recent research using sodium bicarbonate (SB), an individualised approach to administering buffering agents has emerged as a potential method of maximising the likelihood of a performance effect. This entails supplementing SB (or SC) at a pre-determined time before exercise, allowing exercise to commence at peak pH or bicarbonate (HCO3-) levels. The utilization of this strategy is dependent on the reproducibility of these blood acid-base responses, which at present, remains undetermined following SC ingestion. Therefore, Study 1 investigated the reproducibility of blood acid-base responses following the ingestion of SC, provided in multiple quantities. This study revealed that pH and HCO3- had limited reproducibility, irrespective of ingested dose and as such, it would be difficult to recommend an individualised approach. Despite this, SC induced potentially meaningful levels of alkalosis in the absence of significant gastrointestinal symptoms (GIS), suggesting that a positive post-ingestion response could be applied to exercise, potentially utilising a more generalised approach. Subsequent investigations were completed to elucidate the effect of different forms of encapsulation, as well as the effect of a carbohydrate (CHO) rich meal on GIS primarily, whilst also commenting on the specific effects on blood HCO3- kinetics. Study 2 compared three different forms of encapsulation; gelatine (GEL), delayed-release (DEL) and enterically-coated (ENT) capsules. Ingestion form had no significant effect on total GIS experienced, with many participants experiencing no symptoms throughout. Peak GIS typically arose within ~100 min post-ingestion, at a similar time across encapsulation forms and notably, before mean peak blood [HCO3-] responses. Furthermore, while blood [HCO3-] was significantly higher with ENT vs. GEL, all forms induced significant changes in [HCO3-]. Collectively, the need for expensive forms of SC encapsulation was questioned. In study 3, CHO did not notably impact GIS responses or blood HCO3- kinetics. Specifically, total GIS experienced remained similar with or without CHO and was minimal throughout. In reference to blood HCO3- kinetics, no effect of CHO was observed on blood [HCO3-] following SC ingestion. Absolute change in HCO3- was also comparable, with important increases well beyond reported thresholds for a positive effect. Finally, time-to-peak [HCO3-] was highly similar. An interesting finding was the emergence of peak GIS, which occurred almost exclusively in the first sample post-ingestion. While more work is required, this appeared to be the result of co-ingesting large quantities of CHO and encapsulated SC simultaneously, which has implications for future use. Taken together, CHO could be consumed alongside SC to individually support CHO metabolism, without impacting the general response to SC, although quantities consumed may provide a challenge. In study 4, findings from the preceding investigations were utilised to test the effect of ingesting 0.5 g.kg-1 body mass (BM) SC, provided in GEL capsules and alongside a CHO rich meal (1.75 g.kg-1 BM), on repeated 4 km time trial (TT) performance. Specifically, SC was ingested at a generalised time point, aiming to promote a peak [HCO3-] at commencement of the first TT or, at commencement of the second TT. Ingestion of SC in this manner was compared to a placebo and control, revealing significant effects on blood alkalosis ([HCO3-] and pH) which did not translate into performance, physiological or perceptual differences.
|Date of Award||12 Apr 2023|
|Supervisor||ADRIAN MIDGLEY (Director of Studies) & Glyn Howatson (Director of Studies)|