Nathan Philip Hilton

Enhanced buffering capacity following sodium citrate (SC) ingestion may be optimized when subsequent exercise commences at individual time-to-peak (TTP) alkalosis (blood pH or bicarbonate concentration [HCO₃⁻]). While accounting for considerable interindividual variation in TTP (188–300 min), a reliable blood alkalotic response is required for practical use. This study evaluated the reliability of blood pH, HCO₃⁻, and sodium (Na⁺) following acute SC ingestion. Fourteen recreationally active males ingested 0.4 or 0.5 g/kg body mass (BM) of SC on two occasions each and 0.07 g/kg BM of sodium chloride (control) once. Blood pH and HCO₃⁻ were measured for 4 hr postingestion. Blood pH and HCO₃⁻ displayed good reliability following 0.5 g/kg BM SC (r = .819, p = .002, standardized technical error [sTE] = 0.67 and r = .840, p < .001, sTE = 0.63, respectively). Following 0.4 g/kg BM SC, blood HCO₃⁻ retained good reliability (r = .771, p = .006, sTE = 0.78) versus moderate for blood pH (r = .520, p = .099, sTE = 1.36). TTP pH was moderately reliable following 0.5 (r = .676, p = .026, sTE = 1.05) and 0.4 g/kg BM SC (r = .679, p = .025, sTE = 0.91) versus poor for HCO₃⁻ following 0.5 (r = .183, p = .361, sTE = 5.38) and 0.4 g/kg BM SC (r = .290, p = .273, sTE = 2.50). Although the magnitude of (and displacement in) blood alkalosis, particularly HCO₃⁻, appears reliable following potentially ergogenic doses of SC, strategies based on individual TTP cannot be recommended.

To compare the bicarbonate kinetics and gastrointestinal (GI) symptom responses between an equal dose of sodium bicarbonate and sodium citrate using delayed-release capsules. Thirteen active males (age 20.5 ± 2.1 y, height 1.8 ± 0.1 m and body mass [BM] 76.5 ± 9.6 kg) consumed either 0.3 g^.kg⁻¹ BM sodium bicarbonate, sodium citrate or a placebo, using a double-blind, randomized crossover design. Blood bicarbonate ion (HCO₃⁻) concentration, pH and GI symptoms were measured pre-consumption and every 10 min for 180 min post-consumption. Blood HCO₃⁻ concentration (P < 0.001) and pH (P = 0.040) were significantly higher in the sodium bicarbonate condition compared with sodium citrate condition up to 3 h post-consumption. Peak blood HCO₃^– concentration was significantly higher with the sodium bicarbonate compared with citrate (P < 0.001). Mean GI symptom scores were lower (P = 0.037) for sodium citrate (1.5 ± 1.8 AU) than bicarbonate (2.6 ± 3.1 AU), with considerable inter-individual variability. No GI symptoms were reported following consumption of the placebo. Both substances increase HCO₃⁻ values significantly, with sodium bicarbonate causing significantly higher pH and HCO₃⁻ values than the same dose of sodium citrate, but results in slightly more severe GI symptoms.

Purpose: Enteric-coated sodium bicarbonate (NaHCO₃) can attenuate gastrointestinal (GI) symptoms following acute bicarbonate loading, although the subsequent effects on exercise performance have not been investigated. The purpose of this study was to examine the effects of enteric-coated NaHCO₃ supplementation on high-intensity exercise performance and GI symptoms. Methods: Eleven trained male cyclists completed three 4 km time trials after consuming; a placebo or 0.3 g∙kg^–1 body mass NaHCO₃ in enteric-coated or gelatin capsules. Exercise trials were timed with individual peak blood bicarbonate ion concentration ([HCO₃^–]). Blood acid–base balance was measured pre-ingestion, pre-exercise, and post-exercise, whereas GI symptoms were recorded pre-ingestion and immediately pre-exercise. Results: Pre-exercise blood [HCO3⁻] and potential hydrogen (pH) were greater for both NaHCO₃ conditions (P < 0.0005) when compared to placebo. Performance time was faster with enteric-coated (− 8.5 ± 9.6 s, P = 0.044) and gelatin (− 9.6 ± 7.2 s, P = 0.004) NaHCO₃ compared to placebo, with no significant difference between conditions (mean difference = 1.1 ± 5.3 s, P = 1.000). Physiological responses were similar between conditions, although blood lactate ion concentration was higher with gelatin NaHCO₃ (2.4 ± 1.7 mmol∙L^–1, P = 0.003) compared with placebo. Furthermore, fewer participants experienced GI symptoms with enteric-coated (n = 3) compared to gelatin (n = 7) NaHCO₃. Discussion: Acute enteric-coated NaHCO₃ consumption mitigates GI symptoms at the onset of exercise and improves subsequent 4 km cycling TT performance. Athletes who experience GI side-effects after acute bicarbonate loading may, therefore, benefit from enteric-coated NaHCO₃ supplementation prior to exercise performance.

Enteric-formulated capsules can mitigate gastrointestinal (GI) side effects following sodium bicarbonate (NaHCO₃) ingestion; however, it remains unclear how encapsulation alters postingestion symptoms and acid–base balance. The current study aimed to identify the optimal ingestion form to mitigate GI distress following NaHCO₃ ingestion. Trained males (n = 14) ingested 300 mg/kg body mass of NaHCO₃ in gelatin (GEL), delayed-release (DEL), and enteric-coated (ENT) capsules or a placebo in a randomized cross-over design. Blood bicarbonate anion concentration, potential hydrogen, and GI symptoms were measured pre- and postingestion for 3 hr. Fewer GI symptoms were reported with ENT NaHCO₃ than with GEL (p = .012), but not with DEL (p = .106) in the postingestion phase. Symptom severity decreased with DEL (4.6 ± 2.8 arbitrary units) compared with GEL (7.0 ± 2.6 arbitrary units; p = .001) and was lower with ENT (2.8 ± 1.9 arbitrary units) compared with both GEL (p < .0005) and DEL (p = .044) NaHCO₃. Blood bicarbonate anion concentration increased in all NaHCO₃ conditions compared with the placebo (p < .0005), although this was lower with ENT than with GEL (p = .001) and DEL (p < .0005) NaHCO₃. Changes in blood potential hydrogen were reduced with ENT compared with GEL (p = .047) and DEL (p = .047) NaHCO₃, with no other differences between the conditions. Ingestion of ENT NaHCO₃ attenuates GI disturbances for up to 3 hr postingestion. Therefore, ENT ingestion forms may be favorable for those who report GI disturbances with NaHCO₃ supplementation or for those who have previously been deterred from its use altogether.

Background Cystic fibrosis is the most common autosomal recessive disease in white populations, and causes respiratory dysfunction in the majority of individuals. Numerous types of respiratory muscle training to improve respiratory function and health‐related quality of life in people with cystic fibrosis have been reported in the literature. Hence a systematic review of the literature is needed to establish the effectiveness of respiratory muscle training (either inspiratory or expiratory muscle training) on clinical outcomes in cystic fibrosis. This is an update of a previously published review. Objectives To determine the effectiveness of respiratory muscle training on clinical outcomes in people with cystic fibrosis. Search methods We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials register comprising of references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Date of most recent search: 17 April 2018. A hand search of the Journal of Cystic Fibrosis and Pediatric Pulmonology was performed, along with an electronic search of online trial databases up until 07 May 2018. Selection criteria Randomised controlled studies comparing respiratory muscle training with a control group in people with cystic fibrosis. Data collection and analysis Review authors independently selected articles for inclusion, evaluated the methodological quality of the studies, and extracted data. Additional information was sought from trial authors where necessary. The quality of the evidence was assessed using the GRADE system Main results Authors identified 19 studies, of which nine studies with 202 participants met the review's inclusion criteria. There was wide variation in the methodological and written quality of the included studies. Four of the nine included studies were published as abstracts only and lacking concise details, thus limiting the information available. Seven studies were parallel studies and two of a cross‐over design. Respiratory muscle training interventions varied dramatically, with frequency, intensity and duration ranging from thrice weekly to twice daily, 20% to 80% of maximal effort, and 10 to 30 minutes, respectively. Participant numbers ranged from 11 to 39 participants in the included studies; five studies were in adults only and four in a combination of children and adults. No significant improvement was reported in the primary outcome of pulmonary function (forced expiratory volume in one second and forced vital capacity) (very low‐quality evidence). Although no change was reported in exercise capacity as assessed by the maximum rate of oxygen use, a 10% improvement in exercise duration was found when working at 60% of maximal effort in one study (n = 20) (very low‐quality evidence). In a further study (n = 18), when working at 80% of maximal effort, health‐related quality of life improved in the mastery and emotion domains (very low‐quality evidence). With regards to the review's secondary outcomes, one study (n = 11) found a significant change in intramural pressure, functional residual capacity and maximal inspiratory pressure following training (low‐quality evidence). A further study (n = 22) reported that respiratory muscle endurance was significantly longer in the training group (P < 0.01). No studies reported on any other secondary outcomes. Meta‐analyses could not be performed due to a lack of consistency and insufficient detail in reported outcome measures. Authors' conclusions There is insufficient evidence to suggest whether this intervention is beneficial or not. Healthcare practitioners should consider the use of respiratory muscle training on a case‐by‐case basis. Further research of reputable methodological quality is needed to determine the effectiveness of respiratory muscle training in people with cystic fibrosis. Researchers should consider the following clinical outcomes in future studies; respiratory muscle function, pulmonary function, exercise capacity, hospital admissions, and health‐related quality of life. Sensory‐perceptual changes, such as respiratory effort sensation (e.g. rating of perceived breathlessness) and peripheral effort sensation (e.g. rating of perceived exertion) may also help to elucidate mechanisms underpinning the effectiveness of respiratory muscle training.