Multiday acute sodium bicarbonate intake improves endurance capacity and reduces acidosis in men

Effects of acute and multi-day low-dose sodium bicarbonate intake on high-intensity endurance exercise performance in male recreational cyclists

PURPOSE

This study aimed to compare the effects of acute and multi-day low-dose sodium bicarbonate (SB) intake on high-intensity endurance exercise performance.

METHODS

In a randomized, double-blind, cross-over design, twelve recreational male cyclists (age: 31.17 ± 4.91 years; V ˙ O2peak: 47.98 ± 7.68 ml·kg-1·min-1) completed three endurance performance tests following acute SB (ASB, 0.2 g·kg-1 SB), multi-day SB (MSB, 0.2 g·kg-1·day-1 SB for four days), and placebo (PLA) intake. The high-intensity endurance performance was assessed with a cycling exercise test, wherein participants cycled on a bicycle ergometer at 95% of the predetermined anaerobic threshold for 30 min, followed by a time-to-exhaustion test at 110% of the anaerobic threshold. Data were analyzed using one-way and two-way repeated-measures ANOVA.

RESULTS

Significant main effects of supplementation protocol were evident in pre-exercise bicarbonate concentrations (F = 27.93; p < 0.01; partial eta squared (η2) = 0.72; false discovery rate (FDR)-adjusted p value = 0.001). Prior to performance test, blood bicarbonate concentrations were significantly higher in MSB (25.78 ± 1.63 mmol·L-1 [95% CI 26.55-28.44] (p < 0.001; FDR-adjusted p value = 0.001)) and ASB (27.49 ± 1.49 mmol·L-1 [95% CI 24.75-26.81] (p < 0.001; FDR-adjusted p value = 0.007)) compared to PLA (23.75 ± 1.40 mmol·L-1 [95% CI 22.86 to 24.64]). Time-to-exhaustion increased in MSB (54.27 ± 9.20 min [95% CI 48.43-60.12]) compared to PLA (49.75 ± 10.80 min [95% CI 42.89-56.62]) (p = 0.048); however, this increase in MSB did not reach the significance threshold of 1% FDR (FDR-adjusted p value = 0.040). No significant difference was noted in exhaustion times between ASB (51.15 ± 8.39 min [95% CI 45.82-56.48]) and PLA (p > 0.05).

CONCLUSION

Both acute and multi-day administration of low-dose SB improves buffering system in cyclists; nevertheless, neither intervention demonstrates sufficient efficacy in enhancing high-intensity endurance performance.

Use of Buffers in Specific Contexts: Highly Trained Female Athletes, Extreme Environments and Combined Buffering Agents-A Narrative Review

This narrative review evaluated the evidence for buffering agents (sodium bicarbonate, sodium citrate and beta-alanine), with specific consideration of three discrete scenarios: female athletes, extreme environments and combined buffering agents. Studies were screened according to exclusion and inclusion criteria and were analysed on three levels: (1) moderating variables (supplement dose and timing, and exercise test duration and intensity), (2) design factors (e.g., use of crossover or matched group study design, familiarisation trials) and (3) athlete-specific factors (recruitment of highly trained participants, buffering capacity and reported performance improvements). Only 19% of the included studies for the three buffering agents reported a performance benefit, and only 10% recruited highly trained athletes. This low transferability of research findings to athletes' real-world practices may be due to factors including the small number of sodium citrate studies in females (n = 2), no studies controlling for the menstrual cycle (MC) or menstrual status using methods described in recently established frameworks, and the limited number of beta-alanine studies using performance tests replicating real-world performance efforts (n = 3). We recommend further research into buffering agents in highly trained female athletes that control or account for the MC, studies that replicate the demands of athletes' heat and altitude camps, and investigations of highly trained athletes' use of combined buffering agents. In a practical context, we recommend developing evidence-based buffering protocols for individual athletes which feature co-supplementation with other evidence-based products, reduce the likelihood of side-effects, and optimise key moderating factors: supplement dose and timing, and exercise duration and intensity.

Short-Term Consumption of Hydrogen-Rich Water Enhances Power Performance and Heart Rate Recovery in Dragon Boat Athletes: Evidence from a Pilot Study

(1) Background: Exercise that exceeds the body’s accustomed load can lead to oxidative stress and increased fatigue during intense training or competition, resulting in decreased athletic performance and an increased risk of injury, and the new medicinal H₂ may be beneficial as an antioxidant. Therefore, we explored the effect of short-term supplementation of hydrogen-rich water (HRW) on the work performance and fatigue recovery of dragon boat athletes after training. (2) Methods: Eighteen dragon boat athletes who trained for 4 h a day (2 h in the morning and 2 h in the afternoon) were divided into an HRW group (n = 9) and a placebo water (PW) group (n = 9), drinking HRW or PW for 7 days. Each participant completed 30 s rowing dynamometer tests, monitoring the heart rate at baseline (i.e., Day 1) and after the intervention (on Day 8). (3) Result: Drinking HRW increased the maximum power and average power of the 30 s rowing test and decreased the maximum heart rate during the period. After the rowing test, the HRW group’s heart rate dropped significantly after 2 min of recovery, while the PW group’s heart rate did not drop. There was no significant difference between the 30 s rowing distance and the predicted duration of rowing 500 m. (4) Conclusions: Drinking HRW in the short term can effectively improve the power performance of dragon boat athletes and is conducive to the recovery of the heart rate after exercise, indicating that HRW may be a suitable means of hydration for athletes.

Extracellular Buffering Supplements to Improve Exercise Capacity and Performance: A Comprehensive Systematic Review and Meta-analysis

BACKGROUND

Extracellular buffering supplements [sodium bicarbonate (SB), sodium citrate (SC), sodium/calcium lactate (SL/CL)] are ergogenic supplements, although questions remain about factors which may modify their effect.

OBJECTIVE

To quantify the main effect of extracellular buffering agents on exercise outcomes, and to investigate the influence of potential moderators on this effect using a systematic review and meta-analytic approach.

METHODS

This study was designed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Three databases were searched for articles that were screened according to inclusion/exclusion criteria. Bayesian hierarchical meta-analysis and meta-regression models were used to investigate pooled effects of supplementation and moderating effects of a range of factors on exercise and biomarker responses.

RESULTS

189 articles with 2019 participants were included, 158 involving SB supplementation, 30 with SC, and seven with CL/SL; four studies provided a combination of buffering supplements together. Supplementation led to a mean estimated increase in blood bicarbonate of + 5.2 mmol L^-1 (95% credible interval (CrI) 4.7-5.7). The meta-analysis models identified a positive overall effect of supplementation on exercise capacity and performance compared to placebo [ES_0.5 = 0.17 (95% CrI 0.12-0.21)] with potential moderating effects of exercise type and duration, training status and when the exercise test was performed following prior exercise. The greatest ergogenic effects were shown for exercise durations of 0.5-10 min [ES_0.5 = 0.18 (0.13-0.24)] and > 10 min [ES_0.5 = 0.22 (0.10-0.33)]. Evidence of greater effects on exercise were obtained when blood bicarbonate increases were medium (4-6 mmol L^-1) and large (> 6 mmol L^-1) compared with small (≤ 4 mmol L^-1) [β_Small:Medium = 0.16 (95% CrI 0.02-0.32), β_Small:Large = 0.13 (95% CrI - 0.03 to 0.29)]. SB (192 outcomes) was more effective for performance compared to SC (39 outcomes) [β_SC:SB = 0.10 (95% CrI - 0.02 to 0.22)].

CONCLUSIONS

Extracellular buffering supplements generate large increases in blood bicarbonate concentration leading to positive overall effects on exercise, with sodium bicarbonate being most effective. Evidence for several group-level moderating factors were identified. These data can guide an athlete's decision as to whether supplementation with buffering agents might be beneficial for their specific aims.

International Society of Sports Nutrition position stand: sodium bicarbonate and exercise performance

Based on a comprehensive review and critical analysis of the literature regarding the effects of sodium bicarbonate supplementation on exercise performance, conducted by experts in the field and selected members of the International Society of Sports Nutrition (ISSN), the following conclusions represent the official Position of the Society: 1. Supplementation with sodium bicarbonate (doses from 0.2 to 0.5 g/kg) improves performance in muscular endurance activities, various combat sports, including boxing, judo, karate, taekwondo, and wrestling, and in high-intensity cycling, running, swimming, and rowing. The ergogenic effects of sodium bicarbonate are mostly established for exercise tasks of high-intensity that last between 30 s and 12 min. 2. Sodium bicarbonate improves performance in single- and multiple-bout exercise. 3. Sodium bicarbonate improves exercise performance in both men and women. 4. For single-dose supplementation protocols, 0.2 g/kg of sodium bicarbonate seems to be the minimum dose required to experience improvements in exercise performance. The optimal dose of sodium bicarbonate dose for ergogenic effects seems to be 0.3 g/kg. Higher doses (e.g., 0.4 or 0.5 g/kg) may not be required in single-dose supplementation protocols, because they do not provide additional benefits (compared with 0.3 g/kg) and are associated with a higher incidence and severity of adverse side-effects. 5. For single-dose supplementation protocols, the recommended timing of sodium bicarbonate ingestion is between 60 and 180 min before exercise or competition. 6. Multiple-day protocols of sodium bicarbonate supplementation can be effective in improving exercise performance. The duration of these protocols is generally between 3 and 7 days before the exercise test, and a total sodium bicarbonate dose of 0.4 or 0.5 g/kg per day produces ergogenic effects. The total daily dose is commonly divided into smaller doses, ingested at multiple points throughout the day (e.g., 0.1 to 0.2 g/kg of sodium bicarbonate consumed at breakfast, lunch, and dinner). The benefit of multiple-day protocols is that they could help reduce the risk of sodium bicarbonate-induced side-effects on the day of competition. 7. Long-term use of sodium bicarbonate (e.g., before every exercise training session) may enhance training adaptations, such as increased time to fatigue and power output. 8. The most common side-effects of sodium bicarbonate supplementation are bloating, nausea, vomiting, and abdominal pain. The incidence and severity of side-effects vary between and within individuals, but it is generally low. Nonetheless, these side-effects following sodium bicarbonate supplementation may negatively impact exercise performance. Ingesting sodium bicarbonate (i) in smaller doses (e.g., 0.2 g/kg or 0.3 g/kg), (ii) around 180 min before exercise or adjusting the timing according to individual responses to side-effects, (iii) alongside a high-carbohydrate meal, and (iv) in enteric-coated capsules are possible strategies to minimize the likelihood and severity of these side-effects. 9. Combining sodium bicarbonate with creatine or beta-alanine may produce additive effects on exercise performance. It is unclear whether combining sodium bicarbonate with caffeine or nitrates produces additive benefits. 10. Sodium bicarbonate improves exercise performance primarily due to a range of its physiological effects. Still, a portion of the ergogenic effect of sodium bicarbonate seems to be placebo-driven.

Increased Performance in Elite Runners Following Individualized Timing of Sodium Bicarbonate Supplementation

The present study investigated individualized sodium bicarbonate (NaHCO3-) supplementation in elite orienteers and its effects on alkalosis and performance in a simulated sprint orienteering competition. Twenty-one Danish male and female elite orienteers (age = 25.2 ± 3.6 years, height = 176.4 ± 10.9 cm, body mass = 66.6 ± 7.9 kg) were tested twice in order to identify individual time to peak blood bicarbonate (HCO3- peak) following supplementation of 0.3 g/kg body mass NaHCO3 with and without warm-up. The athletes also performed two 3.5 km time-trial runs (TT-runs) following individualized timing of NaHCO3 supplementation (SBS) or placebo (PLA) on separate days in a randomized, double-blind, cross-over design. The occurrence of individual peak HCO3- and pH ranged from 60 to 180 min. Mean HCO3- and pH in SBS were significantly higher compared with PLA 10 min before and following the TT-run (p < .01). SBS improved overall performance in the 3.5 km TT-run by 6 s compared with PLA (775.5 ± 16.2 s vs. 781.4 ± 16.1 s, respectively; p < .05). SBS improved performance in the last half of the TT-run compared with PLA (p < .01). In conclusion, supplementation with NaHCO3 followed by warm-up resulted in individualized alkalosis peaks ranging from 60 to 180 min. Individualized timing of SBS in elite orienteers induced significant alkalosis before and after a 3.5 km TT and improved overall performance time by 6 s, which occurred in the last half of the time trial. The present data show that the anaerobic buffer system is important for performance in these types of endurance events lasting 12-15 min.

Enteric-Coated Sodium Bicarbonate Attenuates Gastrointestinal Side-Effects

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.

Chronic Ingestion of Bicarbonate-Rich Water Improves Anaerobic Performance in Hypohydrated Elite Judo Athletes: A Pilot Study

In combat sports, anaerobic power and anaerobic capacity determine sport performance and the dominant metabolic pathways. The decline in performance during exercise that is attributed to the cumulative effects of fatigue, including excessive accumulation of metabolites, depletion of energy substrates, and water and electrolyte disturbances, seems to be of greatest significance. In our experiment, we evaluated the effectiveness of three weeks of bicarbonate-rich water ingestion on anaerobic performance in a state of hydration and dehydration in elite judo athletes. Eight male, elite judo athletes participated in two single-blind, repeated-measures trials. They were assigned to two hydration protocols, ingesting low mineralized table water and bicarbonate-rich water. Anaerobic performance was evaluated by two 30 s Wingate tests for lower and upper limbs, respectively, under conditions of hydration as well as exercise-induced dehydration. Resting, post-ingestion, and post-exercise concentrations of bicarbonate (HCO₃), urine osmolality (U_OSM), urine specific gravity (U_GRAV), and lactate (La) were measured. The current investigation assessed two related factors that impair anaerobic performance-hypohydration and buffering capacity. High-bicarbonate water ingestion improved buffering capacity, and we demonstrated the potential role of this mechanism and its phenomenon in masking the adverse effects of dehydration in the context of repeated high-intensity anaerobic exercise (HIAE).

Effect of sodium bicarbonate contribution on energy metabolism during exercise: a systematic review and meta-analysis

Background

The effects of sodium bicarbonate (NaHCO₃) on anaerobic and aerobic capacity are commonly acknowledged as unclear due to the contrasting evidence thus, the present study analyzes the contribution of NaHCO₃ to energy metabolism during exercise.

Methods

Following a search through five databases, 17 studies were found to meet the inclusion criteria. Meta-analyses of standardized mean differences (SMDs) were performed using a random-effects model to determine the effects of NaHCO₃ supplementation on energy metabolism. Subgroup meta-analyses were conducted for the anaerobic-based exercise (assessed by changes in pH, bicarbonate ion [HCO₃⁻], base excess [BE] and blood lactate [BLa]) vs. aerobic-based exercise (assessed by changes in oxygen uptake [VO₂], carbon dioxide production [VCO₂], partial pressure of oxygen [PO₂] and partial pressure of carbon dioxide [PCO₂]).

Results

The meta-analysis indicated that NaHCO₃ ingestion improves pH (SMD = 1.38, 95% CI: 0.97 to 1.79, P < 0.001; I² = 69%), HCO₃⁻ (SMD = 1.63, 95% CI: 1.10 to 2.17, P < 0.001; I² = 80%), BE (SMD = 1.67, 95% CI: 1.16 to 2.19, P < 0.001, I² = 77%), BLa (SMD = 0.72, 95% CI: 0.34 to 1.11, P < 0.001, I² = 68%) and PCO₂ (SMD = 0.51, 95% CI: 0.13 to 0.90, P = 0.009, I² = 0%) but there were no differences between VO₂, VCO₂ and PO₂ compared with the placebo condition.

Conclusions

This meta-analysis has found that the anaerobic metabolism system (AnMS), especially the glycolytic but not the oxidative system during exercise is affected by ingestion of NaHCO₃. The ideal way is to ingest it is in a gelatin capsule in the acute mode and to use a dose of 0.3 g•kg^− 1 body mass of NaHCO₃ 90 min before the exercise in which energy is supplied by the glycolytic system.

The effects of a novel bicarbonate loading protocol on serum bicarbonate concentration: a randomized controlled trial

BACKGROUND

Previous studies have shown that sodium bicarbonate ingestion may enhance intense exercise performance, but may also cause severe gastrointestinal distress. The purpose of this study was to determine whether a modified sodium bicarbonate (SB) ingestion protocol would elevate serum bicarbonate concentration more than previous methods without causing gastrointestinal distress.

METHODS

In randomized order, seven (5 men, 2 women) elite middle-distance runners ingested either placebo, Modified SB (600 mg·kg^- 1 over 19.5 h), or Acute SB (300 mg·kg^- 1) in opaque gelatin capsules. Baseline and post-ingestion blood samples were analyzed for bicarbonate, pH, sodium, hematocrit, and lactate. Repeated measures ANOVA (2 time points × 3 conditions) were analyzed to determine differences in serum bicarbonate, lactate, sodium, blood pH, and hematocrit. Gastrointestinal distress was assessed via self-report on a Likert scale of 1-10. Simple (condition) and repeated (time) within-participant contrasts were used to determine the location of any statistically significant main and interaction effects (p ≤ 0.05).

RESULTS

Both Modified SB (7.6 mmol·L^- 1, p < 0.01) and Acute SB (5.8 mmol·L^- 1, p < 0.01) increased serum bicarbonate concentration compared to the placebo (p ≤ 0.05). Post-ingestion serum bicarbonate concentration was significantly higher for the Modified SB (34.7 ± 2.2 mmol·L^- 1, 28.0% increase) trials than the Acute SB (33.5 ± 2.0 mmol·L^- 1, 20.9% increase) trials (p = 0.05). There was no reported severe GI distress in the Modified SB trials, but two cases in the Acute SB trials.

CONCLUSIONS

Modified SB elevated serum bicarbonate concentration more than Acute SB, without any severe gastrointestinal side effects. Consequently, it is recommended that future experimentation involving SB by researchers and athletes use the novel ingestion protocol described in this study due to its potential for improved effectiveness and reduced gastrointestinal impact.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT03813329 . Registered 23 January 2019 - Retrospectively registered.

The Impact of Sodium Bicarbonate on Performance in Response to Exercise Duration in Athletes: A Systematic Review

According to recent literature sodium bicarbonate (NaHCO₃) has been proposed as a performance enhancing aid by reducing acidosis during exercise. The aim of the current review is to investigate if the duration of exercise is an essential factor for the effect of NaHCO₃. To collect the latest studies from electronic database of PubMed, study publication time was restricted from December 2006 to December 2016. The search was updated in July 2018. The studies were divided into exercise durations of > 4 or ≤ 4 minutes for easier comparability of their effects in different exercises. Only randomized controlled trials were included in this review. Of the 775 studies, 35 met the inclusion criteria. Study design, subjects, effects as well as outcome criteria were inconsistent throughout the studies. Seventeen of these studies reported performance enhancing effects after supplementing NaHCO₃. Eleven of twenty studies with exercise duration of ≤ 4 minutes showed positive and four diverse results after supplementing NaHCO₃. On the other hand six of fifteen studies with an exercise duration of >4 minutes showed performance enhancing and two studies showed diverse results. Consequently, the duration of exercise might be influential for inducing a performance enhancing effect when supplementing NaHCO₃, but to which extent, remains unclear due to the inconsistencies in the study results.

Effect of sodium bicarbonate ingestion during 6 weeks of HIIT on anaerobic performance of college students

Background

Past studies have found that sodium bicarbonate ingestion prior to exercise has a performance-enhancing effect on high-intensity exercise. The aim of this study was to investigate the effects of continuous sodium bicarbonate (NaHCO₃) supplementation on anaerobic performance during six weeks of high-intensity interval training (HIIT).

Methods

Twenty healthy college-age male participants were randomly assigned to either the HCO₃⁻ group (SB) or the placebo group (PL), with 10 subjects in each group. Both groups completed 6 weeks (3 days/week) of HIIT with the SB ingesting an orange-flavored solution containing 15 g xylitol and 0.2 g HCO₃⁻/kg body mass during each training day, and PL ingesting a similar beverage that was HCO₃⁻-free. This study separated 6 weeks of training into two stages with different training intensities, with the first 3 weeks at a lower intensity than the second 3 weeks. Blood samples to measure serum HCO₃⁻ were obtained 5 min before and 30 min after the following HIIT training sessions: Week 1, training session 1; week 3, training session 3; week 6, training session 3. Three 30s Wingate tests (WAnT) were conducted before, in the middle, and after the training and the supplementation interventions, with peak power, mean power, and fatigue index obtained during WAnT, and blood lactate and heart rate obtained after WAnT.

Results

Our findings indicate the following: 1) Serum HCO₃⁻ level of SB was significantly higher than PL (p < 0.05) both before and after each HIIT; 2) Relative peak power in WAnT was significantly higher in the SB group after 6 weeks (p < 0.01); 3) Lactate clearance rate and the lactate clearance velocity after 10 min of WAnT were both significantly higher in SB in the post-test (p < 0.01); 4) Heart rate recovery rate at 10 min after WAnT in both SB and PL after 6 weeks were significantly improved (p < 0.01 and p < 0.05, respectively), resulting in no difference between groups on these measures.

Conclusions

These data suggest that supplementation of HCO₃⁻ at the level of 0.2 g/kg body mass before HIIT training enhances the effect of HIIT on anaerobic performance, and improves the blood lactate clearance rate and the blood lactate clearance velocity following anaerobic exercise.

Chronic Ingestion of Sodium and Potassium Bicarbonate, with Potassium, Magnesium and Calcium Citrate Improves Anaerobic Performance in Elite Soccer Players

Anaerobic power and anaerobic capacity significantly influence performance in many sport disciplines. These include prolonged sprints in athletics, swimming, or cycling, and other high intensity intermittent sports, such as soccer or basketball. Considering the association of exercise-induced acidosis and fatigue, the ingestion of potential buffering agents such as sodium bicarbonate, has been suggested to attenuate metabolic acidosis and improve anaerobic performance. Since elite soccer players cover from 200 to 350 m while sprinting, performing 40–60 all out sprints during a game, it seems that repeated sprint ability in soccer players is among the key components of success. In our experiment, we evaluated the effectiveness of chronic supplementation with sodium and potassium bicarbonate, fortified with minerals, on speed and speed endurance in elite soccer players. Twenty-six soccer players participated in the study. The subjects were randomly divided into two groups. The experimental group was supplemented with sodium bi-carbonate and potassium di-carbonate fortified with minerals, while the control group received a placebo. The athletes were tested at baseline and after nine days of supplementation. Anaerobic performance was evaluated by the Repeated Anaerobic Sprint Test (RAST) protocol which involved 6 × 30 m max sprints, separated by 10 s of active recovery. Resting, post ingestion and post exercise concentrations of HCO₃⁻ and blood pH were measured as well as lactate concentration. The current investigation demonstrated a significant increase in RAST performance of elite soccer players supplemented with sodium and potassium bicarbonate along with calcium phosphate, potassium citrate, and magnesium citrate ingested twice a day over a nine-day training period. The improvements in anaerobic performance were caused by increased resting blood pH and bicarbonate levels.

Targeting tumor-associated acidity in cancer immunotherapy

Checkpoint inhibitors, such as cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) and programmed cell death-1 (PD-1) monoclonal antibodies have changed profoundly the treatment of melanoma, renal cell carcinoma, non-small cell lung cancer, Hodgkin lymphoma, and bladder cancer. Currently, they are tested in various tumor entities as monotherapy or in combination with chemotherapies or targeted therapies. However, only a subgroup of patients benefit from checkpoint blockade (combinations). This raises the question, which all mechanisms inhibit T cell function in the tumor environment, restricting the efficacy of these immunotherapeutic approaches. Serum activity of lactate dehydrogenase, likely reflecting the glycolytic activity of the tumor cells and thus acidity within the tumor microenvironment, turned out to be one of the strongest markers predicting response to checkpoint inhibition. In this review, we discuss the impact of tumor-associated acidity on the efficacy of T cell-mediated cancer immunotherapy and possible approaches to break this barrier.

The Critical Power Model as a Potential Tool for Anti-doping

Existing doping detection strategies rely on direct and indirect biochemical measurement methods focused on detecting banned substances, their metabolites, or biomarkers related to their use. However, the goal of doping is to improve performance, and yet evidence from performance data is not considered by these strategies. The emergence of portable sensors for measuring exercise intensities and of player tracking technologies may enable the widespread collection of performance data. How these data should be used for doping detection is an open question. Herein, we review the basis by which performance models could be used for doping detection, followed by critically reviewing the potential of the critical power (CP) model as a prototypical performance model that could be used in this regard. Performance models are mathematical representations of performance data specific to the athlete. Some models feature parameters with physiological interpretations, changes to which may provide clues regarding the specific doping method. The CP model is a simple model of the power-duration curve and features two physiologically interpretable parameters, CP and W′. We argue that the CP model could be useful for doping detection mainly based on the predictable sensitivities of its parameters to ergogenic aids and other performance-enhancing interventions. However, our argument is counterbalanced by the existence of important limitations and unresolved questions that need to be addressed before the model is used for doping detection. We conclude by providing a simple worked example showing how it could be used and propose recommendations for its implementation.

The effect of chronic progressive-dose sodium bicarbonate ingestion on CrossFit-like performance: A double-blind, randomized cross-over trial

Background

Sodium bicarbonate (SB) has been proposed as an ergogenic aid, as it improves high-intensity and resistance exercise performance. However, no studies have yet investigated SB application in CrossFit. This study examined the effects of chronic, progressive-dose SB ingestion on CrossFit-like performance and aerobic capacity.

Methods

In a randomized, double-blind, cross-over trial, 21 CrossFit-trained participants were randomly allocated to 2 groups and underwent 2 trials separated by a 14-day washout period. Participants ingested either up to 150 mg∙kg^-1 of SB in a progressive-dose regimen or placebo for 10 days. Before and after each trial, Fight Gone Bad (FGB) and incremental cycling (ICT) tests were performed. In order to examine biochemical responses, blood samples were obtained prior to and 3 min after completing each exercise test.

Results

No gastrointestinal (GI) side effects were reported during the entire protocol. The overall FGB performance improved under SB by ~6.1% (p<0.001) and it was ~3.1% higher compared to post placebo (PLA_post) (p = 0.040). The number of repetitions completed in each round also improved under SB (mean from baseline: +5.8% to +6.4%). Moreover, in ICT, the time to ventilatory threshold (VT) (~8:25 min SB_post vs. ~8:00 min PLA_post, p = 0.020), workload at VT (~218 W SB_post vs. ~208 W PLA_post, p = 0.037) and heart rate at VT (~165 bpm SB_post vs. ~161 bpm PLA_post, p = 0.030) showed higher SB_post than PLA_post. Furthermore, the maximum carbon dioxide production increased under SB by ~4.8% (from ~3604 mL∙min^-1 to ~3776 mL∙min^-1, p = 0.049). Pyruvate concentration and creatine kinase activity before ICT showed higher SB_post than PLA_post (~0.32 mmol∙L^-1 vs. ~0.26 mmol∙L^-1, p = 0.001; ~275 U∙L^-1 vs. ~250 U∙L^-1, p = 0.010, respectively). However, the small sample size limits the wide-application of our results.

Conclusions

Progressive-dose SB ingestion regimen eliminated GI side effects and improved CrossFit-like performance, as well as delayed ventilatory threshold occurrence.

Practical Issues in Evidence-Based Use of Performance Supplements: Supplement Interactions, Repeated Use and Individual Responses

Current sports nutrition guidelines recommend that athletes only take supplements following an evidence-based analysis of their value in supporting training outcomes or competition performance in their specific event. While there is sound evidence to support the use of a few performance supplements under specific scenarios (creatine, beta-alanine, bicarbonate, caffeine, nitrate/beetroot juice and, perhaps, phosphate), there is a lack of information around several issues needed to guide the practical use of these products in competitive sport. First, there is limited knowledge around the strategy of combining the intake of several products in events in which performance benefits are seen with each product in isolation. The range in findings from studies involving combined use of different combinations of two supplements makes it difficult to derive a general conclusion, with both the limitations of individual studies and the type of sporting event to which the supplements are applied influencing the potential for additive, neutral or counteractive outcomes. The repeated use of the same supplement in sports involving two or more events within a 24-h period is of additional interest, but has received even less attention. Finally, the potential for individual athletes to respond differently, in direction and magnitude, to the use of a supplement seems real, but is hard to distinguish from normal day to day variability in performance. Strategies that can be used in research or practice to identify whether individual differences are robust include repeat trials, and the collection of data on physiological or genetic mechanisms underpinning outcomes.

Time to Optimize Supplementation: Modifying Factors Influencing the Individual Responses to Extracellular Buffering Agents

Blood alkalosis, as indicated by an increased blood bicarbonate concentration and pH, has been shown to be beneficial for exercise performance. Sodium bicarbonate, sodium citrate, and sodium or calcium lactate, can all result in increased circulating bicarbonate and have all independently been shown to improve exercise capacity and performance under various circumstances. Although there is considerable evidence demonstrating the efficacy of these supplements in several sports-specific situations, it is commonly acknowledged that their efficacy is equivocal, due to contrasting evidence. Herein, we discuss the physiological and environmental factors that may modify the effectiveness of these supplements including, (i) absolute changes in circulating bicarbonate; (ii) supplement timing, (iii) the exercise task performed, (iv) monocarboxylate transporter (MCT) activity; (v) training status, and (vi) associated side-effects. The aim of this narrative review is to highlight the factors which may modify the response to these supplements, so that individuals can use this information to attempt to optimize supplementation and allow the greatest possibility of an ergogenic effect.

Methodologies for Investigating Performance Changes With Supplement Use

Many expert sporting bodies now support a pragmatic acceptance of the use of performance supplements which have passed a risk:benefit analysis of being safe, effective, and permitted for use, while also being appropriate to the athlete's age and maturation in their sport. However, gaining evidence of the performance benefits of these supplements is a process challenged by the scarcity of research in relation to the number of available products, and the limitations of the poor quality of some studies. While meta-analyses and systematic reviews can help to provide information about the general use of performance supplements, the controlled scientific trial provides the basis on which these reviews are undertaken, as well as an opportunity to address more specific questions about supplement applications. Guidelines for the design of studies include the choice of well-trained athletes who are familiarized with performance tasks that have been chosen on their basis of their known reliability and validity. Supplement protocols should be chosen to maximize the likely benefits, and researchers should also make efforts to control confounding variables, while keeping conditions similar to real-life practices. Performance changes should be interpreted in light of what is meaningful to the outcomes of sporting competition. Issues that have been poorly addressed to date include the use of several supplements in combination and the use of the same supplement over successive events, both within a single, and across multiple competition days. Strategies to isolate and explain the variability of benefits to individuals are also a topic for future investigation.

Determinants of curvature constant (W') of the power duration relationship under normoxia and hypoxia: the effect of pre-exercise alkalosis

Purpose

This study investigated the effect of induced alkalosis on the curvature constant (W’) of the power-duration relationship under normoxic and hypoxic conditions.

Methods

Eleven trained cyclists (mean ± SD) Age: 32 ± 7.2 years; body mass (bm): 77.0 ± 9.2 kg; VO_2peak: 59.2 ± 6.8 ml·kg⁻¹·min⁻¹ completed seven laboratory visits which involved the determination of individual time to peak alkalosis following sodium bicarbonate (NaHCO₃) ingestion, an environment specific ramp test (e.g. normoxia and hypoxia) and four x 3 min critical power (CP) tests under different experimental conditions. Participants completed four trials: alkalosis normoxia (ALN); placebo normoxia (PLN); alkalosis hypoxia (ALH); and placebo hypoxia (PLH). Pre-exercise administration of 0.3 g.kg⁻¹ BM of NaHCO₃ was used to induce alkalosis. Environmental conditions were set at either normobaric hypoxia (FiO₂: 14.5%) or normoxia (FiO₂: 20.93%).

Results

An increase in W’ was observed with pre-exercise alkalosis under both normoxic (PLN: 15.1 ± 6.2 kJ vs. ALN: 17.4 ± 5.1 kJ; P = 0.006) and hypoxic conditions (ALN: 15.2 ± 4.9 kJ vs. ALN: 17.9 ± 5.2 kJ; P < 0.001). Pre-exercise alkalosis resulted in a larger reduction in bicarbonate ion (HCO₃⁻) concentrations during exercise in both environmental conditions (p < 0.001) and a greater blood lactate accumulation under hypoxia (P = 0.012).

Conclusion

Pre-exercise alkalosis substantially increased W’ and, therefore, may determine tolerance to exercise above CP under normoxic and hypoxic conditions. This may be due to NaHCO₃ increasing HCO₃⁻ buffering capacity to delay exercise-induced acidosis, which may, therefore, enhance anaerobic energy contribution.

Sodium bicarbonate ingestion and individual variability in time-to-peak pH

This study determined variability in time-to-peak pH after consumption of 300 mg kg^-1 of sodium bicarbonate. Seventeen participants (mean ± SD: age 21.38 ± 1.5 years; mass 75.8 ± 5.8 kg; height 176.8 ± 7.6 cm) reported to the laboratory where a resting capillary sample was taken. Then, 300 mg kg^-1 of NaHCO₃ in 450 ml of flavoured water was ingested. Participants rested for 90 min and repeated blood samples were procured at 10 min intervals for 60 min and then every 5 min until 90 min. Blood pH concentrations were measured. Results suggested that time-to-peak pH (64.41 ± 18.78 min) was variable with a range of 10-85 min and a coefficient of variation of 29.16%. A bimodal distribution occurred, at 65 and 75 min. In conclusion, athletes, when using NaHCO₃ as an ergogenic aid, should determine their time-to-peak pH to best utilize the added buffering capacity this substance allows.

Secondary elements of blood pH variation can influence the effort effectiveness based on adaptive changes within a group of elite athletes

Aim

pH is the direct indicator of the body reaction following the activities performed. Establishing precise correlations between pH and blood biochemical parameters might support the balancing of values during periods of marked physical activity.

Method

We conducted a case study in a group of elite rowers. Twelve athletes were included in the study. Monitoring was carried out by collecting biological samples several times a day: in the morning, 80 minutes pre-workout, 12 hours after the last physical effort performed, at two different times, 10 days apart. Determinations were aimed at adapting the reported biochemical parameters depending on the effort performed. The following parameters were monitored: pH, HCO3, pCO2, pO2, BE, SBE, SBC, Ca++, Mg++, LDH, GPT, T-Pro, and Alb.

Results

The mean value of pH found in athletes was 7.41±0.024. The value obtained was significantly correlated to biochemical parameters such as BE (2.32±1.79), SBC (1.67±1.45), SBE (2.70±1.75). However, bicarbonate (HCO3) was statistically significantly related with SBE, SBC, SBE, and pO2, but did not present a strong association with the pH value (p=0.094). However, values such as Alb, Ca++, LDH, BE, SBC are related to pH value as a result of variations in the data submitted.

Conclusions

The processed data evidence the fact that blood pH, in this case, is significantly influenced by a number of indices that correlate energy system activity, individual adaptation to effort, and the recovery process. The parameters under investigation (SBE, SBC, SBE, CPK, LDH) are associated with pH changes that could confirm the recovery efficiency of the athlete, along with a possible metabolic acidosis/alkalosis.

Nutritional Strategies to Modulate Intracellular and Extracellular Buffering Capacity During High-Intensity Exercise

Intramuscular acidosis is a contributing factor to fatigue during high-intensity exercise. Many nutritional strategies aiming to increase intra- and extracellular buffering capacity have been investigated. Among these, supplementation of beta-alanine (~3–6.4 g/day for 4 weeks or longer), the rate-limiting factor to the intramuscular synthesis of carnosine (i.e. an intracellular buffer), has been shown to result in positive effects on exercise performance in which acidosis is a contributing factor to fatigue. Furthermore, sodium bicarbonate, sodium citrate and sodium/calcium lactate supplementation have been employed in an attempt to increase the extracellular buffering capacity. Although all attempts have increased blood bicarbonate concentrations, evidence indicates that sodium bicarbonate (0.3 g/kg body mass) is the most effective in improving high-intensity exercise performance. The evidence supporting the ergogenic effects of sodium citrate and lactate remain weak. These nutritional strategies are not without side effects, as gastrointestinal distress is often associated with the effective doses of sodium bicarbonate, sodium citrate and calcium lactate. Similarly, paresthesia (i.e. tingling sensation of the skin) is currently the only known side effect associated with beta-alanine supplementation, and it is caused by the acute elevation in plasma beta-alanine concentration after a single dose of beta-alanine. Finally, the co-supplementation of beta-alanine and sodium bicarbonate may result in additive ergogenic gains during high-intensity exercise, although studies are required to investigate this combination in a wide range of sports.

Sodium bicarbonate supplementation improved MAOD but is not correlated with 200- and 400-m running performances: a double-blind, crossover, and placebo-controlled study

The aim of the study was to investigate the effects of acute supplementation of sodium bicarbonate (NaHCO3) on maximal accumulated oxygen deficit (MAOD) determined by a single supramaximal effort (MAODALT) in running and the correlation with 200- and 400-m running performances. Fifteen healthy men (age, 23 ± 4 years; maximal oxygen uptake, 50.6 ± 6.1 mL·kg−1·min−1) underwent a maximal incremental exercise test and 2 supramaximal efforts at 110% of the intensity associated with maximal oxygen uptake, which was carried out after ingesting either 0.3 g·kg−1 body weight NaHCO3 or a placebo (dextrose) and completing 200- and 400-m performance tests. The study design was double-blind, crossover, and placebo-controlled. Significant differences were found between the NaHCO3 and placebo conditions for MAODALT (p = 0.01) and the qualitative inference for substantial changes showed a very likely positive effect (98%). The lactic anaerobic contribution in the NaHCO3 ingestion condition was significantly higher (p < 0.01) and showed a very likely positive effect (99% chance), similar to that verified for peak blood lactate concentration (p < 0.01). No difference was found for time until exhaustion (p = 0.19) or alactic anaerobic contribution (p = 0.81). No significant correlations were observed between MAODALT and 200- and 400-m running performance tests. Therefore, we can conclude that both MAODALT and the anaerobic lactic metabolism are modified after acute NaHCO3 ingestion, but it is not correlated with running performance.

Performance Enhancing Diets and the PRISE Protocol to Optimize Athletic Performance

The training regimens of modern-day athletes have evolved from the sole emphasis on a single fitness component (e.g., endurance athlete or resistance/strength athlete) to an integrative, multimode approach encompassing all four of the major fitness components: resistance (R), interval sprints (I), stretching (S), and endurance (E) training. Athletes rarely, if ever, focus their training on only one mode of exercise but instead routinely engage in a multimode training program. In addition, timed-daily protein (P) intake has become a hallmark for all athletes. Recent studies, including from our laboratory, have validated the effectiveness of this multimode paradigm (RISE) and protein-feeding regimen, which we have collectively termed PRISE. Unfortunately, sports nutrition recommendations and guidelines have lagged behind the PRISE integrative nutrition and training model and therefore limit an athletes' ability to succeed. Thus, it is the purpose of this review to provide a clearly defined roadmap linking specific performance enhancing diets (PEDs) with each PRISE component to facilitate optimal nourishment and ultimately optimal athletic performance.

Caffeine, but not bicarbonate, improves 6 min maximal performance in elite rowers

This study examined the ergogenic effects in a 6 min maximal performance test (PT) on 12 elite rowers: 6 open-weight (mean ± SD; 25 ± 1 years, and 92 ± 3 kg) and 6 light-weight (25 ± 3 years, and 73 ± 6 kg), following supplementation with caffeine (CAF), sodium bicarbonate (SB), and the combination of both, in a double-blind randomized placebo (PLA) controlled design. PT was executed on 4 occasions, on separate days within a week, and in a non-fasted state, with standardized training being performed the day before PT. Protocols were as follows: (i) CAF, 3 mg/kg, 45 min prior to PT + calcium as SB-PLA; (ii) SB, 0.3 g/kg, 75 min prior to PT + dextrose as CAF-PLA; (iii) CAF + SB; and (iv) PLA; CAF-PLA + SB-PLA. The total distance in the CAF (1878 ± 97 m) and CAF + SB (1877 ± 97 m) was longer than in the PLA (1865 ± 104 m; P < 0.05) and SB (1860 ± 96 m; P < 0.01). The mean power in CAF (400 ± 58 W) and CAF + SB (400 ± 58 W) was higher than the PLA (393 ± 61 W; P < 0.05) and SB (389 ± 57 W; P < 0.01). In CAF and CAF + SB, power was higher (P < 0.05) relative to PLA in the last half (4-6 min) of PT. Trials with CAF were more effective in light-weight rowers (1.0% ± 0.8% improvement in distance; P < 0.05) than in open-weight rowers (0.3% ± 0.8%; P > 0.05). No difference between interventions was observed for readiness and stomach comfort before PT and perceived exertion during PT. This study demonstrates that caffeine ingestion does improve performance in elite rowing. In contrast sodium bicarbonate does not appear to be ergogenic, but it does not abolish the ergogenic effect of caffeine.

Intra- and inter-day variability in plasma tCO2 concentration in sedentary horses

Sodium bicarbonate and other alkalinising solutions (‘milkshakes’) have been given to horses surreptitiously before exercise to provide exogenous buffering effects. After an initial positive blood test, some accused horse trainers claim that their horses ‘naturally test high’, so some jurisdictions allow a secured quarantine in which the horse is tested multiple times. The objective of this experiment was to determine the intra- and inter-day variability of plasma total CO2 (tCO2) and other plasma strong ions in a group of sedentary horses housed similarly to a quarantine period. The hypothesis was that plasma tCO2 would not remain constant over a multi-day monitoring interval, but would vary measurably during that interval. Eight sedentary (unconditioned) horses were studied for 2 weeks. Horses were acclimated to a climate-controlled indoor environment and an alfalfa-only diet for a minimum of 10 days prior to sampling. Horses were sampled 3 times daily for 5 consecutive days at 7:00, 11:00 and 15:00 h. Blood samples were collected directly into 10 ml heparinised evacuated glass tubes by jugular venipuncture using a double-ended 0.91 mm needle. Samples were chilled until concentrations of plasma tCO2, Na+, K+, and Cl-, were determined within 1-3 h of sampling using an automated serum chemistry analyzer which was calibrated daily using commercial reagents obtained from the manufacturer as well as externally-obtained NIST-traceable calibrating solutions. Mean results documented mild variations in mean plasma tCO2 (range 28.9-31.6 mmol/l), but individual horses’ plasma tCO2 ranged over 4-7 units. Results showed that there was considerable intra- and inter-individual variability in plasma tCO2. Mean pooled tCO2 and measured strong ion difference (SIDm) differed by time-of-day, with both late morning and early afternoon values lower than early morning values (P<0.001). There was a strong positive linear relationship between plasma SIDm and tCO2 (r=0.75, P<0.001).