Sodium bicarbonate (SB) is an ergogenic aid for athletes during repeated bouts of high-intensity exercise (Carr et al., 2011). Substantial anaerobic energy demand causes excessive accumulation of hydrogen cations (H+) within active muscles, leading to declining intramuscular pH (Sahlin, 2014). Ingestion of 0.3 g/kg body mass (BM) SB raises blood bicarbonate (
Competitive soccer matches are characterized by repeated bouts of high-intensity exercise (i.e., two or more successive sprints) across ∼90 min (two 45 min halves) that are interspersed with short recovery periods (∼30 s; Spencer et al., 2005). Elite soccer players perform up to 25 sprint efforts during matches (Gabbett et al., 2013), resulting in the accumulation of H+ within muscles (Bangsbo et al., 2007). Previous work in hockey and cycling demonstrated elevated
Factors such as differences in exercise protocol, participant characteristics, and ingestion timing/dosage likely contribute to equivocal effects of SB during soccer-specific exercise. Inconsistent results might also be explained by gastrointestinal discomfort after SB ingestion (Cameron et al., 2010). One alternative could be PR Lotion (Momentous), which is a topically applied muscle cream purported to deliver SB into systemic circulation via the transdermal route (Prausnitz & Langer, 2008). Gurton, Greally, et al. (2023) reported a 1.9% improvement (p = .036, d = .34) for 8 × 25 m repeated sprint times after PR Lotion. On the other hand, McKay et al. (2020) found PR Lotion did not increase average power during 3 × 30 s Wingate cycling tests (p = .108). Despite contradictory findings, a strong rationale exists for using PR Lotion over traditional SB ingestion approaches, as if it was proven effective, it would eliminate concerns about gastrointestinal side effects. Further placebo-controlled research trials are warranted before conclusions can be drawn regarding PR Lotions’ efficacy.
While oral and topical SB have been shown to improve soccer-specific performance, it is not known whether benefits exist during ecologically valid match play exercise. An athletes’ ability to repeat high-intensity efforts is a key determinant of success in soccer, but it declines toward the latter stages of matches (Bradley et al., 2010). Additional work is needed examining whether oral or topical SB elevate
Methods
Experimental Design
A randomized, double-blind, placebo-controlled, crossover design was employed. Three treatments (oral SB, topical SB, and placebo) were allocated to be received by four participants first, second, and third during experimental trials using a 3 × 3 block randomization design. Sequence order was randomly assigned using an online generator (www.randomization.com).
Participants
Our a priori sample size calculation conducted on G*Power (version 3.1.9.4) revealed that 10 participants were needed to achieve statistical power (β = 0.80; α = .05). This assumed that repeated measures analyses of variance (ANOVA; within-factors) would be used to analyze sprint times (primary outcome) with a medium effect size (partial eta squared,
Preexperimental Phase
Participants were instructed to avoid vigorous exercise, alcohol, caffeine, and foods with a high potential renal acid load 24 hr before each session (Maughan et al., 2004). During familiarization, a 24-hr dietary recall was conducted using self-report food diaries, with participants asked to replicate nutritional intake before subsequent visits. Participants were asked to attend in a 3-hr postprandial state to minimize the influence of potential renal acid load on acid–base balance (Remer, 2001). Visual inspection of food diaries (consistency of food choice, patterns, and portion sizes) by the principal investigator revealed that compliance to dietary controls was met. Experimental trials were separated by 5–7 days to ensure sufficient recovery and washout of interventions. Testing was conducted at a similar time (±2 hr) to control for confounding effects of circadian rhythms on exercise performance (Reilly, 1990).
Familiarization to Soccer-Specific Exercise
Participants performed a 10-min team sport-specific warm-up (Gurton, Greally, et al., 2023). Familiarization involved conducting performance tests and one block of the SAFT90. Three CMJs were performed on an optical measurement system (OptoJump Next, Microgate), with 1 min separating each jump. Next, participants carried out three IAT followed by 8 × 25 m repeated sprints. During both tests, repeated efforts were separated by 30 s, with completion times recorded via light gates (Brower Timing Systems, Draper) placed at the start and end points. Participants then undertook one 15-min block of the SAFT90, including a soccer-specific eccentric movement pattern circuit (IAT, 10 m sprint, 5 m sidestepping, three headers, backwards running, and a shooting drill) designed to increase ecological validity of our study protocol. The SAFT90 comprised shuttle running and utility movements over a 20-m distance, with participants first sidestepping around one pole (2 m distance) before running forwards through the course, navigating a further three poles (9, 10, and 11 m distance; Small et al., 2010). An audio compact disk was used to provide verbal signals to control the exercise intensity (“stand,” “walk,” “jog,” “stride,” “sprint”) and activity (“upwards,” “sideways”).
Experimental Procedures
Participants performed three separate experimental trials, with an overview of timings and measurements outlined in Figure 1. On arrival to the laboratory, baseline capillary blood samples were analyzed for acid–base balance, strong ions, and lactate. Gastrointestinal discomfort and cooling sensations questionnaires were also completed. Participants then received either oral SB, topical SB or placebo, and a carbohydrate-rich meal (1.5 g/kg BM; biscuits, gels, cereal bars, and cornflakes with milk) over 30 min. They were not permitted to consume any additional food. Water was consumed ad libitum (1,115 ± 465 ml) during the first trial, with equal volumes provided during subsequent sessions. Gastrointestinal discomfort, cooling sensations, and blinding questionnaires were completed postsupplementation and prewarm-up. Capillary blood samples were repeated prewarm-up. Participants started the warm-up 105 min postsupplementation, with the first bout of performance tests (pre-SAFT90) commencing 120 min postsupplementation. This time frame was chosen as peak changes in blood pH are thought to occur ∼120 min after applying PR Lotion (Gibson et al., 2023). Participants performed six 15-min blocks of the SAFT90 (∼100 min total exercise time with soccer-specific movement patterns). Blocks 1–3 and 4–6 were separated by a 15-min recovery period to simulate half-time. Soccer-specific movement patterns were completed before and after each block. Participants repeated performance tests at half-time and post-SAFT90. Capillary blood samples were measured again for acid–base balance and strong ions during half-time and postexercise. Additional blood samples were analyzed for lactate postwarm-up, after performance tests, and following both halves of the SAFT90. Gastrointestinal discomfort was measured during half-time and postexercise. Blinding questionnaires were repeated postexercise.
—Experimental schematic showing timings and measurements during simulated soccer match play exercise protocol (∼4 hr). Soccer-specific exercise tests included three countermovement jumps, three Illinois agility circuits, and eight 25-m repeated sprints. Supplements were given as three separate doses across the 30-min window. ABB = acid–base balance (blood pH, bicarbonate), strong ions (sodium, potassium, calcium); GI = gastrointestinal discomfort questionnaire (visual analog scales for eight symptoms).
Citation: International Journal of Sport Nutrition and Exercise Metabolism 34, 6; 10.1123/ijsnem.2024-0059
Supplementation Protocol
During experimental trials, participants received either: (a) 0.3 g/kg BM SB in capsules and 0.9036 g/kg BM placebo lotion (SB-ORAL), (b) placebo capsules and 0.9036 g/kg BM PR Lotion (SB-LOTION), and (c) placebo capsules and 0.9036 g/kg BM placebo lotion (PLA). Supplements were prepared by a laboratory technician. Size 0 vegetarian capsules (Your Supplements) were filled using a capsule filling device (ALL-IN Capsule) and contained ∼0.8 g SB (Health Leads Ltd.) or ∼0.4 g corn flour (Sainsbury’s). Capsule size influences acid–base balance pharmacokinetics after SB ingestion, with peak changes in
Measurements and Questionnaires
Capillary blood samples (95 μl) were analyzed for pH,
Statistical Analysis
Grouped data and standardized residuals were assessed for normality using Shapiro–Wilk tests. Homogeneity of variance/sphericity was analyzed using Mauchly tests, and violations were corrected via Greenhouse–Geisser adjustments. To determine the reproducibility of soccer-specific exercise tests, typical error of measurement (% TEM) and ICC’s were calculated between familiarization and PLA. Two-way mixed-model, absolute agreement ICC’s were interpreted as poor (r < .50), moderate (r = .50–.75), good (r = .75–.90), or excellent (r > .90; Koo & Li, 2016). Repeated-measures two-way ANOVA were used to investigate Treatment × Time interactions for normally distributed data. When significant interactions were observed, post hoc tests were performed to assess treatment effects across individual time points and time effects within treatments. Otherwise, pairwise comparisons were used to examine main effects for treatment and time. Bonferroni correction factors were used to adjust p values for multiple comparisons. Existence of learning effects was examined via repeated-measures two-way ANOVA by comparing average sprint time, agility time, and CMJ height from the first, second, and third trials. Effect sizes for ANOVA main effects and interactions were reported as
Results
Soccer-Specific Exercise Performance
Repeated sprint performance was highly reproducible, with fastest and average sprint times showing low TEM (2.3%, 2.8%) and good ICC’s (r = .89, .82). Treatment × Time interactions existed for fastest (F[4,36] = 3.733, p = .012,
—(A) Fastest and (B) average times during the 8 × 25 m repeated sprint tests. Bars represent mean values; n = 10. Individual treatment differences depicted by symbol/line. Symbols denote significance (p < .05): *SB-ORAL versus PLA. #SB-ORAL versus SB-LOTION and PLA. †Decline in sprint times for SB-LOTION and PLA, but not SB-ORAL. ‡Decline in sprint times for all treatments. RST1/2/3 = Repeated Sprint Test 1 (pre-SAFT90), 2 (half-time), and 3 (post-SAFT90); SAFT90 = 90-min soccer-specific aerobic field test.
Citation: International Journal of Sport Nutrition and Exercise Metabolism 34, 6; 10.1123/ijsnem.2024-0059
Agility performance was highly reproducible, with fastest and average sprint times showing low TEM (3.1%, 3.0%) and good ICC’s (r = .83, .85). No Treatment × Time interactions existed for fastest (p = .071) or average (p = .143) times, but there were main effects for treatment and time (p < .001; Figure 3A–3B). Treatment main effects revealed quicker fastest times for SB-ORAL compared with SB-LOTION (3.1%, p = .018) and PLA (4.9%, p = .004), but not for SB-LOTION compared with PLA (p = .206). Treatment main effects revealed faster average times for SB-ORAL compared with SB-LOTION (3.1%, p = .007) and PLA (4.9%, p = .002) but not for SB-LOTION compared with PLA (p = .123).
—(A) Fastest and (B) average times during the Illinois agility tests. Bars represent mean values; n = 10. Individual treatment differences depicted by symbol/line. Symbols denote significance (p < .05): **Main effect for treatment (SB-ORAL faster than SB-LOTION and PLA. IAT1/2/3 = Illinois Agility Test 1 (pre-SAFT90), 2 (half-time), and 3 (post-SAFT90); PLA = placebo; SAFT90 = 90-min soccer-specific aerobic field test.
Citation: International Journal of Sport Nutrition and Exercise Metabolism 34, 6; 10.1123/ijsnem.2024-0059
Jump height was highly reproducible, with maximum and average CMJ height showing low TEM (3.4%, 2.8%) and excellent ICC’s (r = .98, .98). No Treatment × Time interactions existed for maximum (p = .207) or average (p = .105) height. There were no treatment or time main effects for maximum (p = .731, p = .201) or average (p = .794, p = .226) height.
No learning effects existed for soccer-specific performance. Irrespective of the order participants completed treatments, performance during the first, second, and third trials was similar, with no Order × Time interactions for the repeated sprint (F[1.49,13.42] = 0.936, p = .390), agility (F[4,36] = 0.383, p = .819), or CMJ (F[2.29,20.62] = 0.651, p = .552) tests.
Blood Metabolites
Treatment × Time interactions existed for blood pH (F[6,54] = 3.802, p = .003,
—Blood lactate response throughout the simulated soccer exercise. Values are presented as mean ± SD; n = 10. Some error bars removed for clarity. RST1/2/3 = Repeated Sprint Test 1 (pre-SAFT90), 2 (half-time), and 3 (post-SAFT90); PLA = placebo; SAFT90 = 90-min soccer-specific aerobic field test.
Citation: International Journal of Sport Nutrition and Exercise Metabolism 34, 6; 10.1123/ijsnem.2024-0059
With respect to SB-ORAL, blood pH and
Blood Acid–Base Balance From Baseline to Postexercise
| Baseline | Prewarm-up | Half-time | Postexercise | |
|---|---|---|---|---|
| pH (au) | ||||
| SB-ORAL | 7.42 ± 0.01 | 7.48 ± 0.04# | 7.46 ± 0.04* | 7.46 ± 0.05 |
| SB-LOTION | 7.41 ± 0.02 | 7.42 ± 0.03 | 7.41 ± 0.02^ | 7.43 ± 0.03 |
| PLA | 7.41 ± 0.02 | 7.41 ± 0.03 | 7.39 ± 0.03 | 7.42 ± 0.03 |
| SB-ORAL | 25.6 ± 1.3 | 30.6 ± 2.0# | 26.9 ± 4.6# | 26.9 ± 4.8 |
| SB-LOTION | 25.6 ± 1.6 | 25.9 ± 1.6 | 22.6 ± 2.2 | 23.9 ± 1.8 |
| PLA | 25.4 ± 1.3 | 25.5 ± 1.1 | 21.8 ± 1.2 | 22.4 ± 1.8 |
Note. Values are presented as mean ± SD; n = 10. SB = sodium bicarbonate; PLA = placebo.
*SB-ORAL versus PLA; ^SB-LOTION versus PLA; #SB-ORAL versus SB-LOTION and PLA (p < .05).
Strong Ion Concentration From Baseline to Postexercise
| Baseline | Prewarm-up | Half-time | Postexercise | |
|---|---|---|---|---|
| Na+ (mmol/L) | ||||
| SB-ORAL | 135 ± 2 | 137 ± 2 | 139 ± 2 | 138 ± 3 |
| SB-LOTION | 135 ± 3 | 137 ± 2 | 138 ± 4 | 141 ± 4^ |
| PLA | 135 ± 2 | 135 ± 2 | 138 ± 2 | 138 ± 2 |
| K+ (mmol/L) | ||||
| SB-ORAL | 4.6 ± 0.4 | 4.3 ± 0.3 | 4.1 ± 0.5* | 3.9 ± 0.4† |
| SB-LOTION | 4.3 ± 0.3 | 4.2 ± 0.4 | 4.3 ± 0.4^ | 4.8 ± 0.7 |
| PLA | 4.4 ± 0.4 | 4.3 ± 0.3 | 4.9 ± 0.5 | 4.6 ± 0.6 |
| iCa2+ (mmol/L) | ||||
| SB-ORAL | 0.81 ± 0.08 | 0.73 ± 0.09 | 0.67 ± 0.06# | 0.67 ± 0.06# |
| SB-LOTION | 0.80 ± 0.12 | 0.78 ± 0.05 | 0.75 ± 0.08 | 0.78 ± 0.09 |
| PLA | 0.77 ± 0.09 | 0.80 ± 0.09 | 0.76 ± 0.06 | 0.77 ± 0.06 |
Note. Values are presented as mean ± SD; n = 10. SB = sodium bicarbonate; PLA = placebo.
Symbols denote significance: *SB-ORAL versus PLA; ^SB-LOTION versus PLA; †SB-ORAL versus SB-LOTION; #SB-ORAL versus SB-LOTION and PLA (p < .05).
With respect to SB-LOTION, blood pH was elevated compared with PLA during half-time (p = .019). Half-time K+ was lower than PLA (p = .012). Postexercise Na+ was higher compared with PLA (p = .008). All other comparisons for SB-LOTION were nonsignificant (p > .05).
Rating of Perceived Exertion
No Treatment × Time interactions existed for RPE during repeated sprints (p > .05) with only a main effect for time (p < .001). A Treatment × Time interaction existed for RPE during the SAFT90 (F[3.34,30.02] = 3.220, p = .032,
—Rating of perceived exertion throughout the SAFT90. Values are presented as mean ± SD; n = 10. Some error bars removed for clarity. Symbols denote significance (p < .05) at individual time points: **SB-LOTION lower than SB-ORAL and PLA; ‡SB-LOTION lower than SB-ORAL. RPE = rating of perceived exertion; PLA = placebo; SAFT90 = 90-min soccer-specific aerobic field test.
Citation: International Journal of Sport Nutrition and Exercise Metabolism 34, 6; 10.1123/ijsnem.2024-0059
Gastrointestinal Discomfort, Blinding, and Cooling Sensation
In general, gastrointestinal discomfort was mild for each treatment (Table 3); however, a treatment effect was shown postsupplementation (χ2[2] = 7.824, p = .026), with aggregate gastrointestinal higher after SB-LOTION compared with PLA (Z = 1.100, p = .042). Only a single participant identified SB-ORAL and PLA postsupplementation and prewarm-up; however, more correct ratings were recorded postexercise (SB-ORAL: 3/10; PLA: 4/10). Five participants identified SB-LOTION from the “stronger cooling effect” (3/5) and “thicker texture” (2/5), but the number of correct and incorrect ratings was similar between treatments (p > .05; Table 4). Treatment effects existed for cooling sensations postsupplementation for the thighs (χ2[2] = 6.452, p = .040) and prewarm-up for the calves (χ2[2] = 12.069, p = .002). Cooling for the thighs was greater postsupplementation for SB-LOTION (−2 [1] au) compared with SB-ORAL (−1 [1] au, Z = 2.236, p = .025) but not PLA (−1 [2] au, p = .264) and for the calves prewarm-up for SB-LOTION (−1 [1] au) compared with SB-ORAL (0 [0] au, Z = 2.236, p = .025) and PLA (0 [1] au, Z = 2.795, p = .005).
Aggregate Gastrointestinal Discomfort Score From Baseline to Postexercise
| Baseline | Postsupplementation | Prewarm-up | Half-time | Postexercise | |
|---|---|---|---|---|---|
| SB-ORAL | 15 [22] | 24 [30] | 26 [28] | 20 [20] | 23 [15] |
| SB-LOTION | 22 [17] | 22 [24]* | 25 [20] | 25 [35] | 26 [24] |
| PLA | 11 [27] | 16 [24] | 17 [36] | 18 [37] | 27 [28] |
Note. Values presented as median [interquartile range]. Aggregate gastrointestinal discomfort score (out of 800 mm) calculated from sum of visual analog scales for eight symptoms. SB = sodium bicarbonate; PLA = placebo.
Symbols denote significance: *exacerbated compared with PLA (p < .05).
Treatment Assignment Ratings for Each of the Three Interventions
| SB-ORAL | SB-LOTION | PLA | |
|---|---|---|---|
| Postsupplementation | |||
| Correct ratings | 1 (10%) | 5 (50%) | 1 (10%) |
| Incorrect ratings | 0 (0%) | 0 (0%) | 1 (10%) |
| Unsure ratings | 9 (90%) | 5 (50%) | 8 (80%) |
| Prewarm-up | |||
| Correct ratings | 1 (10%) | 5 (50%) | 1 (10%) |
| Incorrect ratings | 1 (10%) | 0 (0%) | 2 (20%) |
| Unsure ratings | 8 (80%) | 5 (50%) | 7 (70%) |
| Postexercise | |||
| Correct ratings | 3 (30%) | 5 (50%) | 4 (40%) |
| Incorrect ratings | 2 (20%) | 1 (10%) | 2 (20%) |
| Unsure ratings | 5 (50%) | 4 (40%) | 4 (40%) |
Note. Percentage of treatment assignment ratings displayed in parenthesis. Number of correct guesses recorded greater than expected by chance alone (>33%) are highlighted in bold.
Discussion
The aim of this study was to investigate the effect of oral and topical SB during simulated soccer match play exercise. Our primary finding was that SB-ORAL improved repeated sprint performance during simulated soccer exercise, with sprint times ∼4% faster during half-time and post-SAFT90 compared with PLA. Ergogenic benefits were less pronounced during IAT and CMJ, with only positive main effects for treatment in favor of SB-ORAL for agility performance. No significant improvements in performance were observed for SB-LOTION throughout. Blood buffering capacity was increased prewarm-up and during half-time for SB-ORAL, with small elevations in blood pH for SB-LOTION during half-time. Blood K+ was reduced for SB-ORAL during half-time and postexercise, but only during half-time for SB-LOTION. Finally, RPE was lower during the first and second bouts of the SAFT90 for SB-LOTION, although positive effects wore off throughout exercise.
Blood buffering capacity was elevated for SB-ORAL, with prewarm-up changes in
Of note, however, was that sprint times were ∼3.5% faster during half-time for SB-ORAL compared with PLA. Positive effects were less clear for IAT performance, with only main effects for treatment in favor of SB-ORAL. Greater emphasis on cognitive and technical components (e.g., speed accuracy) during agility tests (Young et al., 2015) may minimize ergogenic benefits after SB, whereas repeated sprints are limited by the accumulation of metabolic by-products (McNaughton et al., 2016). Improved repeated sprint times for SB-ORAL were likely underpinned by greater blood buffering capacity and regulation of strong ions. First, elevated blood pH and
No improvements in repeated sprint performance were reported during half-time for SB-LOTION, with small positive changes in blood pH and K+ compared with PLA, which expands on previous findings (Gurton, Greally et al., 2023; McKay et al., 2020). Improved repeated sprint performance for oral but not topical SB could be explained by differences in blood buffering capacity and strong ion concentration, as these were consistently lower for SB-LOTION. Gibson et al. (2023) documented marked increases in blood pH (+0.04 au) after applying 80 g PR Lotion (∼1.23 g/kg BM), suggesting that larger doses of PR Lotion might elicit a greater rise in pH and thus be more likely to improve performance, but dose–response investigations are warranted to elucidate this theory. Interestingly, SB-LOTION attenuated RPE during the first and second SAFT90 blocks. We previously hypothesized that reduced RPE for PR Lotion is due to an interaction between menthol and residual SB molecules that forms a protective layer over the skin to intensify localized cooling sensations (Gurton, Greally, et al., 2023). At present, this remains speculative, meaning future experimental research should examine whether an interaction exists, but it is based off theoretical knowledge that menthol induces cooling sensations by stimulating membrane-bound ion channel transient receptor potential melastatin 8 (Rosales et al., 2024). Importantly, despite the placebo lotion also containing menthol, greater cooling sensations were reported for SB-LOTION, inferring SB molecules somehow contributed to stronger cooling sensations. These may have resulted in analgesic effects that alleviated localized muscle discomfort (Pan et al., 2012) and caused participants’ feelings of muscle pain to be lower than their actual degree of fatigue (Johar et al., 2012). This offers some insight to how SB-LOTION reduced RPE during the SAFT90. Nonetheless, as RPE was similar from Blocks 3 to 6, it appears effects wore off during exercise.
Sprint times were ∼4.5% faster for SB-ORAL post-SAFT90 compared with SB-LOTION and PLA. Combined with SB-ORAL offsetting decline in fastest sprint times, it appears oral SB improves repeated sprint ability until the latter stages of soccer matches. In contrast, Macutkiewicz and Sunderland (2018) showed no effect of SB on hockey-specific skilled performance in female athletes following 60 min intermittent exercise. Inconsistent findings could relate to sex-specific differences (Durkalec-Michalsk et al., 2020). Our male soccer players likely had larger Type II muscle fibers that rely heavily on glycolysis for adenosine triphosphate production (Simoneau & Bouchard, 1989), meaning they had more to gain from SB. Unlike previous studies (Gurton, Greally, et al., 2023; Krustrup et al., 2015), nonsignificant increases in lactate were observed for SB-ORAL, suggesting performance benefits were not attributed to upregulated glycolytic flux. Instead, reduced blood K+ post-SAFT90 for SB-ORAL reaffirms that preserved muscle excitability may have contributed to improved performance (Cairns & Lindinger, 2008). Once again, repeated sprint and IAT times were not improved for SB-LOTION post-SAFT90, likely as neither blood buffering nor strong ion regulation was improved compared to PLA. Therefore, it seems PR Lotion is not an effective ergogenic aid during soccer matches. One finding that remains difficult to explain was elevated postexercise Na+ (∼3 mmol/L) for SB-LOTION. Our study is the first to examine PR Lotion over ∼4 hr, so it is possible transdermal delivery of Na+ takes longer than initially thought.
Strengths, Limitations, and Practical Applications of the Study
One of this study’s strengths was recruiting collegiate-level soccer players. Specifically, the high level of test reproducibility, combined with the absence of order effects, confirms participants were familiarized to soccer-specific exercise, meaning improvements for SB-ORAL were not attributed to learning effects. Second, oral SB was successfully blinded, allowing us to conclude ergogenic benefits were due to pharmacological properties of SB (Gurton, Matta, et al., 2023). This study’s main limitation was that five participants identified SB-LOTION, which may have induced placebo effects that influenced study outcomes (Hurst et al., 2020). Depending on participants expectancy of positive benefits, identifying PR Lotion could have contributed to lower RPE during the SAFT90.
Practical implications of our results are that oral SB is the most effective supplementation approach for improving blood buffering capacity and repeated sprint performance during soccer match play exercise. Negligible, or less pronounced, effects were shown for IAT and CMJ. Considerably, fewer benefits were reported for topical SB, adding to equivocal findings for the efficacy of PR Lotion (Gurton, Greally et al., 2023; McKay et al., 2020). Interestingly, oral SB caused milder gastrointestinal discomfort compared with previous studies (Cameron et al., 2010; Gurton et al., 2020). Splitting SB supplementation across 30 min likely alleviates gastrointestinal side effects; however, SB must be trialed on an individual basis, as symptoms may still occur. It is recommended that practitioners take the results of this study into consideration when incorporating SB into nutritional regimes for soccer players.
Conclusions
Ingesting 0.3 g/kg BM SB improved repeated sprint ability throughout simulated soccer exercise. Elevated blood buffering capacity and greater regulation of strong ions likely underpinned ergogenic effects. PR Lotion did not improve soccer-specific performance, although reductions in RPE and elevated blood pH suggest some benefits might exist. Consuming SB orally in capsules is a more effective strategy than topical SB for improving blood buffering capacity and repeated sprint performance throughout soccer matches.
Acknowledgments
The authors acknowledge the participation and dedication of all participants. In addition, they would like to thank the laboratory technicians (Benjamin Price and Scott Elliott) for their preparation of supplements and provision of equipment. Author Contributions: Conceptualization and methodology: Gurton, Gough, Siegler, Lynn, Ranchordas. Formal analysis: Gurton, Siegler, Lynn, Ranchordas. Investigation: Gurton. Project administration: Gurton. Resources: Gurton, Lynn, Ranchordas. Original draft: Gurton, Gough. Review and editing: Gurton, Gough, Siegler, Lynn, Ranchordas. All authors approved the final version of the paper. Conflict of Interests: Momentous provided the lotions used in this study free of charge but had no influence over the study design or in preparation of the manuscript. The results of this study do not constitute endorsement of the product by the authors or the journal. Funding Sources: Momentous are funding a Ph.D. studentship at Sheffield Hallam University (for which this study is one output), but no additional funding was received to assist with the preparation of this manuscript.
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