Beta-Alanine Supplementation for CrossFit^® Performance

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

This manuscript effectively examined the beta-alanine effect on CrossFit performance but shows no significant improvements in performance, RPE, or RER. However, the observed interaction for RER suggests a potential role in buffering acidity which merits further research.  Some suggestions:

1.    The double-blind, placebo-controlled design of the study is good and contributing to the reliability of the results. The experienced CrossFit participants selection is appropriate but small sample size may limit the generalizability of the findings. Expanding the study with larger sample sizes and some varied protocols could offer more conclusive insights into beta-alanine ergogenic potential.

2.     Details regarding participant selection, including inclusion and exclusion criteria, are effectively described. Author can include demographic information about the participants also which may enhance the understanding of the sample population.

3.     The statistical analyses are appropriate but further clarification on the criteria for significance (e.g., p-values) and how multiple comparisons were handled would improve result representation.

4.     The dosing scheme for BA supplementation is defined, but adding brief discussion on why chosen dosage and duration were selected in relation to existing literature would more add depth in manuscript.

5.     The method to examine performance, RER, and RPE is clearly articulated. However, it would be valuable to include more specific details on how RER was measured like timing of measurements relative to exercise phases.

6.     The exploration of the RER and its implications for understanding metabolic responses during high-intensity workouts is a strong aspect of the discussion. However, further clarification on the physiological significance of the observed changes in RER would enhance this section.

 

7.     Examine paresthesia side effect in the beta-alanine treated group is an important aspect but it would be more valuable to discuss how this might have affected participant performance and perceptions during the workout.

 

 

Comments on the Quality of English Language

Minor changes needed.

Author Response

Thanks for the review of our manuscript. We have responded to all comments below and have highlighted the changes in our revised manuscript.

This manuscript effectively examined the beta-alanine effect on CrossFit performance but shows no significant improvements in performance, RPE, or RER. However, the observed interaction for RER suggests a potential role in buffering acidity which merits further research.  Some suggestions:

 

1. The double-blind, placebo-controlled design of the study is good and contributing to the reliability of the results. The experienced CrossFit participants selection is appropriate but small sample size may limit the generalizability of the findings. Expanding the study with larger sample sizes and some varied protocols could offer more conclusive insights into beta-alanine ergogenic potential.

Response: We have highlighted the low sample size in our limitations section (lines 305-312) and have also suggested that further research should also be undertaken examining different CrossFit routines (lines 323-325).

 

2. Details regarding participant selection, including inclusion and exclusion criteria, are effectively described. Author can include demographic information about the participants also which may enhance the understanding of the sample population.

Response: Table 1 contains detailed description of the participants’ demographic information. After the study was completed, we decided to also determine peak oxygen consumption on the participants to describe their aerobic fitness. Seven of the twelve participants who completed the initial phase of the study agreed to this assessment. Their data have been added to Table 1. This testing indicates the participants were highly trained.

A description of this testing has also been added to the end of the methods section (lines 133-139).

3. The statistical analyses are appropriate but further clarification on the criteria for significance (e.g., p-values) and how multiple comparisons were handled would improve result representation.

Response: The p-value used (0.05) is indicated at the end of the statistics section. We have recognized that there could be inflation of type I error with multiple statistical testing in our limitations section: “A p-value of 0.05 was used for all statistical testing. There is a possibility of inflation of type I error with multiple comparisons in our study.” (lines 312-313)

4. The dosing scheme for BA supplementation is defined, but adding brief discussion on why chosen dosage and duration were selected in relation to existing literature would more add depth in manuscript.

Response: We have added to the methods: “This dose of beta-alanine was chosen because significant exercise improvements are typically observed with doses ranging from 3.2-6.4g/day [7,17].” (lines 86-88)

We have also included in the discussion that four weeks is the typical beta-alanine supplement duration to show improvement in performance; therefore, our supplement duration may have been too short. (lines 318-321)

5. The method to examine performance, RER, and RPE is clearly articulated. However, it would be valuable to include more specific details on how RER was measured like timing of measurements relative to exercise phases.

Response: In the methods we have added clarity to the timing of RER measurements: “Respiratory exchange ratio was assessed throughout the entire workout without any demarcation for exercise phases.” (lines 100-101)

6. The exploration of the RER and its implications for understanding metabolic responses during high-intensity workouts is a strong aspect of the discussion. However, further clarification on the physiological significance of the observed changes in RER would enhance this section.

Response: We added the following to the discussion: “At high exercise intensities, carbon dioxide output increases out of proportion to oxygen consumption in conjunction with increased lactic acid appearance. This causes an increase in RER, with values greater than 1.1 (as seen during the Fran workout in the current study; Figure 2) indicating participants were working at intensities close to their peak aerobic capacity [1].” (lines 252-256)

We also added “...the subsequent decrease in RER to pre-test levels can potentially be attributed to BA’s role in intracellular buffering [10]. Relative to the 25% time point, this would decrease blood acidity, potentially affecting CO2 output relative to oxygen consumption and decreasing RER.” (lines 268-271).

 

7. Examine paresthesia side effect in the beta-alanine treated group is an important aspect but it would be more valuable to discuss how this might have affected participant performance and perceptions during the workout.

Response: We have added to the limitations section at the end of the manuscript that this could have potentially had a negative impact on performance. (line 323)

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review this paper. While the study design and findings are strong, a few areas could be clarified to further enhance the quality of the manuscript. These revisions would strengthen the paper’s contribution. 

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for their comments. We have responded to comments below and have highlighted changes in our revised manuscript.

Methods: Please explain how the sample size was determined for this study. Was a

power analysis conducted to ensure the study was adequately powered?

Response: An a-priori sample size calculation was difficult to perform because this was the first study to evaluate the effects of beta-alanine on CrossFit performance. We attempted to determine an adequate sample size in the limitations section and have added the following: “It was difficult to determine an a-priori sample size because there are no previous studies using beta-alanine supplementation during CrossFit® exercises. Other studies that have evaluated a similar dose and duration of beta-alanine supplementation as used in the current study resulted in an improvement in supramaximal cycling time to exhaustion of 15.2 seconds compared to -2.4 seconds for a placebo group, with standard deviation of 16.6 seconds [27]. Using an alpha of 0.05 and power of 80%, this indicates a required sample size of 15 per group, indicating we may have been underpowered in our study.” (lines 305-312)

 

Line 61: What criteria within the Get Active Questionnaire (GAQ) were used to clear

participants for physical activity?

Response: We have added more detail on this to the manuscript: “This questionnaire screens for cardiovascular disease or chest pain, high blood pressure (with a cutoff of 160/90 mmHg), dizziness/lightheadedness during physical activity, shortness of breath at rest, loss of consciousness/fainting, concussion, acute injury, arthritis, back pain, diabetes, cancer, osteoporosis, asthma, and spinal cord injury. Participants needed to answer “no” to each of these to be included.” (lines 62-66)

 

Lines 62-64: Why were certain performance-enhancing supplements like beta-alanine

excluded, but others like caffeine and creatine allowed? Can you please explain how

this might affect the consistency of results?

Response: We decided to allow other performance-enhancing supplements as long as participants were on a stable dose for at least a month because we thought it would not be feasible to recruit a sufficient number of CrossFit participants if taking any supplements was an exclusion criterion. Most CrossFit participants (>80%) take nutritional supplements. We have added this as a limitation at the end of the manuscript: “In our study we included participants who had been taking stable doses of other nutritional supplements for at least one month and this may have influenced results. We decided it would not be feasible to recruit CrossFit® athletes by excluding athletes taking any nutritional supplement because the majority of CrossFit® athletes (>80%) regularly take nutritional supplements [27].” (lines 314-318)

 

Protocol:

Please explain how randomization of participants into the BA and placebo groups was

carried out. Were any steps taken to ensure group equivalence in terms of training

experience and physical fitness?

Response: We have added greater detail on the randomization process: “Participants were stratified by sex and randomly assigned to either the BA or placebo (PLA) group in a 1:1 ratio in blocks of four using an online random number generator (https://www.calculator.net/random-number-generator.html).” (lines 79-82)

Although this only ensured that groups were equally divided by sex, Table 1 indicates that the random allocation was sufficient for ensuring groups were carefully matched. We have added to table 1 measures of aerobic fitness (i.e. VO2peak determined on a treadmill test) which was evaluated at the end of the study (we have added this to the methods and the results; lines 133-139). Again, this indicates that groups were closely matched for physical fitness during the study.

 

Line76: Please elaborate on why 6.4g of beta-alanine (BA) was chosen as the

supplementation dose. Especifically, is there evidence supporting this specific dosage

for the targeted outcomes?

Response: We added the following to justify the dose: “This dose of beta-alanine was chosen because significant exercise improvements are typically observed with doses ranging from 3.2-6.4g/day [7,17].” (lines 86-88)

 

Lines 88-89: How was the reliability of the COSMED K5 metabolic system ensured

throughout the testing sessions? Were there any measures in place to account for

potential calibration errors or technical issues?

Response: Before each testing session, the COSMED K5 was calibrated for flow using a 3 L syringe and calibrated against known gas concentrations for oxygen and carbon dioxide. This has been added to the methods. (lines 98-100)

 

Statistical Analysis:

Please indicate which statistical software was used for all analyses.

Response: This has been added to the manuscript: “Statistics were evaluated using Statistica 7.0 (Statsoft, Chicago, IL).” (line 154)

Discussion:

Lines: 200-201: The discussion about internal pacing strategies during performance

tests could be expanded. It would be useful to see if there are suggestions for future

studies that might control or minimize these pacing effects to better capture BA’s

potential impact.

Response: We have added the following suggestion: “Future studies evaluating effects of BA could focus on events that are limited by time to exhaustion (i.e., total exercise capacity) rather than performance, which might be subject to pacing.” (lines 225-227)

 

Lines216-224: The study contrasts its findings with Stein et al., suggesting the absence

of a learning effect due to the participants' prior familiarity with the workout. It might

be helpful to provide more data or background to support this claim, possibly

including more detailed pre-study experience logs from participants.

Response: We had asked the participants how long they had been doing CrossFit and how many were experienced with the specific “Fran” workout used for the study. This data is presented in Table 1. Overall, participants had about 6.7 years experience doing CrossFit workouts and 11 out of 12 participants had previously done “Fran” workouts of the day.

We have added the following to the end of this paragraph: “Our participants were very experienced with CrossFit® workouts, having a mean of 6.7y years CrossFit® experience with 11 of the 12 participants who completed the study having previous experience with the “Fran” WOD.” (lines 247-249)

 

Lines 235-238: The discussion notes that differences in movements during the

metabolic tests could lead to differences in the RER. How was the consistency of

2 movement patterns between pre- and post-tests ensured? Were there any attempts to

standardize which movements were performed during gas analysis?

Response: This would have been impossible to do without compromising the validity of the Fran workout. We have added the following to clarify that RER was measured throughout the workout rather than during specific movement patterns: “Respiratory exchange ratio was assessed throughout the entire workout without any demarcation for exercise phases.” (lines 100-101)

 

Lines 272-275: The authors acknowledged the small sample size as a limitation. It

would be useful to explore this more deeply, perhaps suggesting that a power analysis

could provide more context about whether the study was adequately powered to

detect differences.

Response: We have added the following to address this limitation in more detail: “It was difficult to determine an a-priori sample size because there are no previous studies using beta-alanine supplementation during CrossFit® exercises. Other studies that have evaluated a similar dose and duration of beta-alanine supplementation as used in the current study resulted in an improvement in supramaximal cycling time to exhaustion of 15.2 seconds compared to -2.4 seconds for a placebo group, with standard deviation of 16.6 seconds [26]. Using an alpha of 0.05 and power of 80%, this indicates a required sample size of 15 per group, indicating we may have been underpowered in our study.” (lines 305-312)

 

Lines 272-275: The intervention length of three weeks is cited as potentially insufficient

for observing BA’s ergogenic effects. This could be emphasized more, especially in

comparison with studies that have used longer durations (e.g. Smith et al). Could the

authors further clarify why three weeks were chosen despite evidence suggesting

longer durations are needed?

Response: We have added to the limitations section: “Our study duration of 3-weeks may have been insufficient to observe beneficial effects of BA: Previous studies have indicated beneficial effects using similar doses of BA as used in the current study in 4-12 weeks [7,17]. We chose a 3-week duration mainly due to participants’ availability during the university semester.” (lines 318-321)

 

Lines 274-275: The issue of paresthesia affecting 50% of the BA group is briefly

mentioned. Could this have affected blinding and, subsequently, the results? It might

be worth expanding on how this was managed.

Response: This would have been very difficult to manage regarding blinding, as we were ethically required in our consent form to state that this was a possible side-effect. We did not suggest participants reduce the dosage of beta-alanine because this side effect was considered quite mild. We have recognized that this might have affected blinding and perhaps exercise performance in the limitations section. (line 323)

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is providing a valuable information about b-Alanine on cross-fit performance. The authors have effectively addressed all previous suggestions which strengthened the overall quality of the paper. The data is well-presented, and the conclusions drawn are supported by the findings. No further corrections are necessary, and I recommend this manuscript for publication.

Comments on the Quality of English Language

Minor changes are needed for clarity in the English.

Author Response

Thanks for reviewing our manuscript.