To swim or not to swim after eating: a randomised controlled crossover feasibility trial

Sehriban Harmankaya; Stina Öberg; Jesper Ryg; Marianne Vogsen; Jacob Rosenberg

doi:10.12688/f1000research.142691.1

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Brief Report

To swim or not to swim after eating: a randomised controlled crossover feasibility trial

[version 1; peer review: 1 approved with reservations]

Sehriban Harmankaya¹, Stina Öberg¹, Jesper Ryg², Marianne Vogsen³, Jacob Rosenberg ¹

Sehriban Harmankaya¹, Stina Öberg¹, [...] Jesper Ryg², Marianne Vogsen³, Jacob Rosenberg ¹

PUBLISHED 14 Dec 2023

Author details Author details

¹ Department of Surgery, Herlev and Gentofte Hospital, University of Copenhagen, Herlev, 2730, Denmark
² Department of Geriatric Medicine, Odense University Hospital, Odense, Denmark
³ Department of Oncology, Odense University Hospital, Odense, Denmark

Sehriban Harmankaya
Roles: Conceptualization, Data Curation, Formal Analysis, Investigation, Methodology, Project Administration, Writing – Original Draft Preparation

Stina Öberg
Roles: Conceptualization, Data Curation, Investigation, Methodology, Project Administration, Writing – Review & Editing

Jesper Ryg
Roles: Conceptualization, Data Curation, Investigation, Methodology, Writing – Review & Editing

Marianne Vogsen
Roles: Conceptualization, Data Curation, Investigation, Methodology, Writing – Review & Editing

Jacob Rosenberg
Roles: Conceptualization, Data Curation, Investigation, Methodology, Supervision, Writing – Review & Editing

OPEN PEER REVIEW

REVIEWER STATUS

Abstract

Background

The aim was to investigate and challenge the belief that swimming immediately after eating is dangerous and also to investigate what potentially could happen when swimming immediately after a meal. We wanted to explore feasibility and get background data to perform sample size calculations and choose outcome parameters for a full-scale randomized trial.

Methods

The trial was performed during lunch breaks at a medical writing course in Turkey in June 2022. Participants were randomised on the first trial day to swim 14 meters breaststroke immediately after lunch or wait 30 minutes after eating, with crossover on the second trial day. Main outcomes measures were mortality, and mood, discomfort, and adverse events were assessed in participant-reported questionnaires. Participants completed a Profile of Mood States-Adolescents questionnaire, a visual analogue scale for discomfort, and a questionnaire of adverse events after each swim.

Results

A total of 26 participants completed the trial. No cases of mortality, drowning, resuscitation, side stitch, or muscle cramps were reported. The participants reported no significant difference in their mood states after each swim and no significant difference was found regarding the participants’ swimming time (P = 0.53). However, more discomfort was reported when swimming immediately instead of 30 minutes after eating (P = 0.05).

Conclusions

It seems that swimming after eating is safe since no mortality or cramps were registered. However, a significant level of discomfort was found when swimming immediately after eating lunch. This feasibility trial provides background data for a future full-scale randomised trial.

Clinicaltrials.gov registration

NCT05401396 (25/05/2022).

Keywords

Eating, swimming, cramps, crossover trial

Corresponding author: Jacob Rosenberg

Competing interests: No competing interests were disclosed.

Grant information: The author(s) declared that no grants were involved in supporting this work.

Copyright: © 2023 Harmankaya S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

How to cite: Harmankaya S, Öberg S, Ryg J et al. To swim or not to swim after eating: a randomised controlled crossover feasibility trial [version 1; peer review: 1 approved with reservations]. F1000Research 2023, 12:1593 (https://doi.org/10.12688/f1000research.142691.1) First published: 14 Dec 2023, 12:1593 (https://doi.org/10.12688/f1000research.142691.1) Latest published: 14 Dec 2023, 12:1593 (https://doi.org/10.12688/f1000research.142691.1)

Introduction

There is a common belief that swimming immediately after having a meal is dangerous and might cause cramps that potentially could lead to drowning.¹ Interestingly, the World Health Organization does not mention food intake before swimming as a risk factor for drowning.² This narrative about the danger of swimming or playing in water immediately after eating is regarded by many as a myth.³ Nevertheless, many still believe it to be true. It is doubtful how long this belief has flourished, however, in a manual for boy scouts from 1908, the author instructed the scouts to avoid bathing in deep water right after a meal as this could cause cramps resulting in drowning.⁴ According to the narrative, one should usually wait half an hour to two hours after having a meal before swimming.⁵ After a meal, postprandial hyperemia occurs with increased blood flow to the gut resulting in less peripheral circulation.⁶ This is probably one explanation to why there is a fear of less peripheral blood circulation resulting in cramps. In contrast, synchronous swimmers with an intense exercise program are encouraged to consume a well-balanced diet both before, during, and after the exercise.⁷

A review of relevant research in the field found no direct association between food intake before swimming and fatal outcomes such as drowning.¹ The review found a few observational studies conducted in the 1960s that assessed the impact of eating and swimming after different time intervals. No effect on swimming performance or any case of discomfort with nausea or cramping were reported.¹ Nonetheless, to our knowledge, no randomised study has been conducted to assess the danger of swimming after eating. In order to provide background data for a future full scale randomised trial enabling sample size calculations based on proper choice of outcome parameters, we chose to perform a feasibility study. With the current feasibility study and a future full scale randomised trial, we wanted to challenge the myth that it may be dangerous to swim immediately after eating.

Materials and methods

The trial was conducted over two days as a randomised controlled trial with a crossover design. We have reported the study according to the Consolidated Standards of Reporting Trials (CONSORT) statement extension to randomised crossover trials,⁸^,¹² and the trial was registered at www.clinicaltrials.gov (NCT05401396) before initiation on 25^th May 2022.

The study and collection of data were conducted during lunch-breaks at a research retreat at a hotel in Turkey in June 2022 with participants from Denmark.

Participants

Participants were researchers attending the writing course. They were eligible for inclusion if they were adults, could swim, and complied with local pool regulations.

Setting

The lunch restaurant and the pool area were in close proximity. Participants received written information about the study by e-mail one week before departure and were informed orally on the day of departure at the airport. The water temperature and pH were constant on the study days, being 29 °C and 7.6, respectively, whereas the weather temperature ranged from 29–32 °C. The pool was 1.4 meters deep and 7 meters wide, making the total swimming distance 14 meters.

Intervention

On the first trial day, participants were randomised to either swim immediately after lunch or 30 minutes after. On the second day, each participant crossed over and performed the opposite of either swimming immediately or 30 minutes after lunch. The trial course is illustrated in Figure 1. The trial intervention was swimming immediately after eating while the control was waiting 30 minutes, hence every participant served as their own control. The participants were instructed to have lunch as they normally would to reflect their usual behaviors. Participants who swam 30 minutes after lunch jumped in the water 30 minutes after their last bite. Participants who swam immediately after eating were observed when walking from the dining table to the pool to ensure that they ate until they arrived at the pool area.

Figure 1. Illustration of each step of the first and second day of the trial.

Baseline vital signs of blood pressure and oxygen saturation were measured during lunch on the first trial day. Blood pressures were measured with a blood pressure monitor (Seagull-Healthcare, model HL888HA, Taipei, Taiwan) and oxygen saturation with a fingertip pulse oximeter (CONTEC LED CMS50M Pulse Oximeter, China). Participants were instructed to walk and slowly enter the pool by the ladder and swim breaststroke briskly with their head over the water. Up to three participants swam simultaneously with the presence of lifeguards and observers in case of any incidents. The time to complete the swimming distance was noted on all participants. Immediately after swimming, the participants filled in three questionnaires: the validated Profile of Mood States – Adolescents (POMS-A) questionnaire,⁹^,¹⁰ a visual analogue scale (VAS) about discomfort, and a self-reported questionnaire on adverse advents.

User involvement

The trial was designed and conducted in collaboration with a professional lifeguard, an experienced swimmer, and a restaurant chef to reflect user perspectives. Each user reviewed the study protocol and provided valuable insight and feedback to the research team. The lifeguard provided information on the impact of swimming distance and mentioned that during swimming competitions, he regularly experienced parents forcing their children not to swim immediately after eating. The experienced swimmer focused on the importance of swimming style, which had to be identical on both days. He also stressed the importance of swimming at the same timepoint as performance might vary throughout the day. The previous Michelin restaurant chef expressed no concerns about the safety of the trial, but he experienced many restaurant guests being tired and inflated after eating a meal. Therefore, he worried that the participants might lack amusement and attention when swimming immediately after eating.

Outcomes

As this was a feasibility trial, we arbitrarily chose the primary outcome to be mortality after swimming. Secondary outcomes included differences in POMS-A, discomfort, adverse events, pulse rate, and swimming time. The adjectives in the POMS-A questionnaire were translated to Danish using back- and forward translation by two authors and face-validation was performed on two different laymen. The POMS-A questionnaire evaluates mood by focusing on different categories involving tension, depression, anger, fatigue, confusion, and vigour with adjectives in each category on a five-point scale from one to five. The scores for each category were calculated by adding the raw scores from the adjectives for the specific category. A high vigour score and low scores on the other five categories indicate a person with a more stable and positive mood profile. The VAS was face-validated and measured current level of any discomfort, ranging from no discomfort to the worse imaginable discomfort (0–100 mm). Furthermore, a questionnaire of adverse events was developed within the author group for the participants to self-report (see Extended data¹²). Face-validation was performed to ensure the correct interpretation of the questions. The questionnaire assessed adverse events such as drowning, resuscitation, experience of any gastrointestinal symptoms, side stitch, or muscle cramps both during and immediately after swimming. Since all participants served as their own control, secondary outcomes were assessed as the difference between outcomes on the two study days, i.e., swimming immediately versus 30 minutes after eating.

Randomisation

Randomisation of each participant was performed by the same investigator by throwing dice at the dining table after each participant had selected their lunch. Participants with an even dice number were randomised to swim immediately after lunch the first day, while participants with an uneven dice number were randomised to wait 30 minutes.

Statistical methods

Convenience sampling was used, hence, participants were included based on availability, time, and interest. The statistical analyses were performed in SPSS Statistics 28 (IBM). Continuous data were assessed for normal distribution by visual inspection of histograms and QQ-plots. Since data were not normally distributed, continuous data are presented as median, interquartile range (IQR), and range and were analysed with the Wilcoxon signed-rank test. Categorical data are presented as numbers and percentages and were analyzed with the Fisher’s exact test since expected values were <5 in at least one cell. POMS-A is an ordinal categorical scale, however, it was handled as continuous data in our statistical analyses. We considered statistical significance when P ≤ 0.05.

Ethical approval

According to Danish legislation, the Regional Ethics Committee in Copenhagen waived ethical approval (journal number 22020290). Written consent was obtained from every participant before participation, and data were stored in a secure database.

Results

A total of 31 medical researchers attended the writing course, and 27 participants were eligible for inclusion. A flowchart of the inclusion process, participation, and randomisation is illustrated in Figure 2. Unfortunately, one participant dropped out since she was dropped in the pool by some of her colleagues after being randomised and having lunch on the first day. Consequently, 26 participants were included and completed the trial as intended with 100% complete data. The baseline characteristics of the study participants are illustrated in Table 1.

Figure 2. A flow diagram depicting the number of participants who were randomly assigned to 0 minutes or 30 minutes the first trial day, who received the allocated sequence the second trial day, and who were analysed for the outcomes.

n: number.

Table 1. Participant characteristics and vital signs at baseline.

Participant characteristics	Participant, n = 26
Sex, n (%)
Male	10 (38)
Female	16 (62)
Age in years, median (IQR)	31 (27–38)
Vital signs at baseline Day 1	Participant, n = 27
Saturation in %, median (IQR)	98 (98–98)
Blood pressure in mmHg, median (IQR)
Diastolic	84 (79–91)
Systolic	126 (116–123)

Adverse events

No cases of mortality were registered. Similarly, no adverse events of drowning, resuscitation, and experience of any side stitch or muscle cramps were found. Two participants reported gastrointestinal symptoms while swimming 30 minutes after lunch: one participant experienced flatulence and the other participant reported a bloated feeling. However, there was no statistically significant difference in gastrointestinal symptoms when comparing the intervention and control (P = 0.41).

Visual Analogue Scale of discomfort

Participants reported their level of discomfort with a median VAS of 2 (scale 0–100) both after swimming immediately (range 0–34, IQR: 0–4) and after 30 minutes (range 0–4, IQR: 0–3) after lunch (Table 2). However, when swimming 30 minutes after lunch, the participants reported significantly less discomfort compared with swimming immediately after lunch (P = 0.05).

Table 2. Overall reported results of swimming immediately and 30 minutes after having lunch.

Swimming time is reported in seconds, pulse is reported per minute, and level of discomfort is reported in millimeters based on a visual analogue scale. IQR: interquartile range; VAS: visual analogue scale; P: p-value.

Outcomes	Intervention Swimming immediately after lunch	Control Swimming 30 minutes after lunch	Difference Intervention-Control	P
Reported with median (IQR, range)
Pulse rate	82 (71–89, 61–150)	82 (72–92, 51–129)	0 (-7–7, -29–64)	0.99
Discomfort (VAS)	2 (0–4, 0–34)	2 (0–3, 0–4)	0 (0–3, -4–32)	0.05
Swimming time	17 (15–20, 10–31)	16 (14–20, 13–24)	0 (-1–2, -4–9)	0.53
Profile of Mood States–Adolescents, median (range)
Anger	0 (0–5)	0 (0–8)	0 (-3–2)	0.85
Confusion	0 (0–5)	0 (0–7)	0 (-3–5)	0.30
Depression	0 (0–3)	0 (0–8)	0 (-5–1)	0.70
Fatique	1 (0–7)	1 (0–5)	0 (-2–3)	0.09
Tension	0 (0–1)	0 (0–8)	0 (-8–1)	0.68
Vigour	6 (0–15)	7 (2–16)	-1 (-7–5)	0.23

Profile of Mood States – Adolescents

The participants’ mood profile was assessed for the six mood categories of tension, depression, anger, fatigue, confusion, and vigour. After calculating the participants’ mood score when swimming immediately and 30 minutes after lunch for each category, we found no significant difference (Table 2). Overall, the participants’ mood weighted to be more positive than negative with a high vigour score and low scores in the negative mood categories. The reported median vigour score was 6 when swimming immediately and 7 when swimming 30 minutes after lunch (P = 0.23). Similarly, no significant difference was found among the negative mood categories of tension, depression, anger, fatigue, and confusion (Table 2).

Swimming time and pulse rate

We found no significant difference (P = 0.53) when comparing the participants’ performance in swimming time when they swam immediately or 30 minutes after lunch (Table 2). The observed median swimming time was 17 seconds (IQR: 15–20) and 16 seconds (IQR: 14–20) when swimming immediately and half an hour after eating, respectively (P = 0.53). Furthermore, the participants’ pulse rate was measured after each swim and no significant difference was found (P = 0.99) with a median of 82 beats per minute on both days.

Discussion

This trial showed that swimming 14 meters in a pool with limited depth immediately or half an hour after lunch did not result in any deaths or other serious adverse events. Furthermore, the overall result of the trial did not find differences in the mood categories after the two swimming regimens. The only disadvantage when swimming immediately after lunch was a higher level of discomfort compared with swimming half an hour after.

There are some important limitations to this trial. Since the participants were all from Denmark where the population rarely swim in outdoor pools, some level of adaptation might have occurred on the second trial day. Nevertheless, an equal number of participants were randomly distributed to undergo the intervention or comparison swim during day 1 and 2. A further limitation is that it remains unknown whether the participants had lunch as they usually would since they were in a hotel with plenty of food, however, no participants informed the investigators that they overate or were on a diet. A strength of the trial was that we required the participants to follow the local pool regulations. Another strength is that the design of the trial minimised recall bias since the participants filled the questionnaires immediately after each swim. Furthermore, the POMS-A, VAS, and questionnaire of adverse events were face-validated thoroughly, which avoided any potential misinterpretations and thereby optimised the assessment. Another strength is the user involvement in the design phase of the trial, thus reflecting user perspectives of swimming after eating.

A recent study found that the time-of-day (morning or evening) can influence the swimming performance in an adolescent population with swimming experience, however, with variations depending on the swimming distance and sex.¹¹ The importance of varying performance depending on the time-of-day was also stressed by the experienced swimmer involved in the design phase and we minimised this time-of-day variance in our study since the participants swam during the lunch breaks on both days. The same study also demonstrated the importance of sleep quality as a factor influencing participants’ level of anxiety and depression, consequently affecting their performance in swimming.¹¹ Since our study investigated an adult population during a course with an intense scientific program, it is possible that the participants worked from early mornings til late nights, which could have affected their swimming performance because of less sleep.

Since this study found that swimming directly after a meal was not dangerous, we judge it to be safe to perform a full-scale randomised trial with swimming directly after eating as long as routine safety instructions are followed. However, swimmers may expect a higher level of discomfort when swimming directly after a meal, and this parameter seems to be the obvious primary outcome for a future randomised trial. Our data can be used as background data for sample size calculations for such a full-scale trial, which may employ different swimming distances and/or swimming in sea water rather than in a pool.

Conclusions

In conclusion, we found that swimming immediately after eating seems to be unhazardous and safe but may in some be associated with discomfort. The present feasibility trial, being the first randomised trial on the subject, will form basis for future large scale conclusive trials.

Data availability

Underlying data

Zenodo: To swim or not to swim after eating: a randomized controlled crossover feasibility trial. https://doi.org/10.5281/zenodo.10074765.¹²

This project contains the following underlying data:

Reporting guidelines

Zenodo: CONSORT checklist for ‘To swim or not to swim after eating: a randomized controlled crossover feasibility trial’. https://doi.org/10.5281/zenodo.10074765.¹²

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).

References

1. Chambers P, Quan L, Wernicke P, et al.: American red cross scientific advisory committee scientific review: eating before swimming. Int. J. Aquat. Res. Educ. 2011; 5: 483–492. Publisher Full Text
2. World Health Organization: Drowning.[Cited 2022 Sept 18]. Reference Source
3. Bartholdy K, Hoff A: 100 myter om sundhed og sygdom. 1st ed.Denmark: FADL; 2015.
4. Baden-Powell R: Scouting for boys: the original. 1908th ed.United States of America: Dover Publications; 2007.
5. Britannica: The editors of encyclopaedia Britannica. Is it really dangerous to swim after eating?[Cited 2022 Sept 18]. Reference Source
6. Jeays AD, Lawford PV, Gillott R, et al.: A framework for the modeling of gut blood flow regulation and postprandial hyperaemia. World J. Gastroenterol. 2007; 13: 1393–1398. PubMed Abstract | Publisher Full Text | Free Full Text
7. Robertson S, Benardot D, Mountjoy M: Nutritional recommendations for synchronized swimming. Int. J. Sport Nutr. Exerc. Metab. 2014; 24: 404–413. PubMed Abstract | Publisher Full Text
8. Dwan K, Li T, Altman DG, et al.: CONSORT 2010 statement: extension to randomised crossover trials. BMJ. 2019; 366: l4378. 31. Publisher Full Text
9. Terry PC, Lane AM, Lane HJ, et al.: Development and validation of a mood measure for adolescents. J. Sports Sci. 1999; 17: 861–872. Publisher Full Text
10. Terry PC, Lane AM, Fogarty GJ: Construct validity of the profile of mood states – adolescents for use with adults. Psychol. Sport Exerc. 2003; 4: 125–139. Publisher Full Text
11. Nunes RSM, Freitas AFL, Vieira E: The influence of time of day on the performance of adolescent swimmers. Chronobiol. Int. 2021; 38: 1177–1185. PubMed Abstract | Publisher Full Text
12. Harmankaya S, Öberg S, Ryg J, et al.: To swim or not to swim after eating: a randomized controlled crossover feasibility trial. [Data set]. Zenodo. 2023. Publisher Full Text

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Version 1

VERSION 1 PUBLISHED 14 Dec 2023

Author details Author details

¹ Department of Surgery, Herlev and Gentofte Hospital, University of Copenhagen, Herlev, 2730, Denmark
² Department of Geriatric Medicine, Odense University Hospital, Odense, Denmark
³ Department of Oncology, Odense University Hospital, Odense, Denmark

Sehriban Harmankaya
Roles: Conceptualization, Data Curation, Formal Analysis, Investigation, Methodology, Project Administration, Writing – Original Draft Preparation

Stina Öberg
Roles: Conceptualization, Data Curation, Investigation, Methodology, Project Administration, Writing – Review & Editing

Jesper Ryg
Roles: Conceptualization, Data Curation, Investigation, Methodology, Writing – Review & Editing

Marianne Vogsen
Roles: Conceptualization, Data Curation, Investigation, Methodology, Writing – Review & Editing

Jacob Rosenberg
Roles: Conceptualization, Data Curation, Investigation, Methodology, Supervision, Writing – Review & Editing

Competing interests

No competing interests were disclosed.

Grant information

The author(s) declared that no grants were involved in supporting this work.

Article Versions (1)

version 1

Published: 14 Dec 2023, 12:1593

https://doi.org/10.12688/f1000research.142691.1

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© 2023 Harmankaya S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Harmankaya S, Öberg S, Ryg J et al. To swim or not to swim after eating: a randomised controlled crossover feasibility trial [version 1; peer review: 1 approved with reservations]. F1000Research 2023, 12:1593 (https://doi.org/10.12688/f1000research.142691.1)

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Reviewer Report 08 Feb 2024

Antonio Laguna Camacho, Autonomous University of the State of Mexico, Toluca, Mexico

Approved with Reservations

https://doi.org/10.5256/f1000research.156266.r239263

The submitted manuscript describes an experiment in which participants reported experiencing more discomfort when swimming immediately after lunch compared to when swimming 30 minutes after lunch.

The authors note that this was a feasibility trial and that ... Continue reading

The submitted manuscript describes an experiment in which participants reported experiencing more discomfort when swimming immediately after lunch compared to when swimming 30 minutes after lunch.

The authors note that this was a feasibility trial and that the data will be used for sample size calculations. However, the sample size of the reported experiment was small, which likely resulted in underpowered results.

Although the authors mention that eligible participants took part in the experiment, the manuscript lacks information on the eligibility criteria. Furthermore, there is no mention in the manuscript regarding the information provided to participants about the experiment.

Please address potential limitations arising from participants' reports aligning with researchers' expectations or from participants' beliefs that swimming immediately after eating causes adverse events.

Additionally, please clarify whether the analyses were conducted within subjects; for example, were the data from both sequences combined and then intervention and control conditions were compared.

I am curious why a mood scale for adolescents was applied if the participants were adults.

Finally, I question whether the median swimming time of only 17 seconds was a limitation and whether longer swimming times would contribute to adverse events.

Is the work clearly and accurately presented and does it cite the current literature?

Partly
Is the study design appropriate and is the work technically sound?

Partly
Are sufficient details of methods and analysis provided to allow replication by others?

Partly
If applicable, is the statistical analysis and its interpretation appropriate?

Partly
Are all the source data underlying the results available to ensure full reproducibility?

Yes
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: Psychology; Nutrition; Behaviour change; Experimental research

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

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Antonio Laguna Camacho, Autonomous University of the State of Mexico, Toluca, Mexico

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08 Feb 2024 | for Version 1

Antonio Laguna Camacho, Autonomous University of the State of Mexico, Toluca, Mexico

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Approved With Reservations

The submitted manuscript describes an experiment in which participants reported experiencing more discomfort when swimming immediately after lunch compared to when swimming 30 minutes after lunch.

The authors note that this was a feasibility trial and that the data will be used for sample size calculations. However, the sample size of the reported experiment was small, which likely resulted in underpowered results.

Although the authors mention that eligible participants took part in the experiment, the manuscript lacks information on the eligibility criteria. Furthermore, there is no mention in the manuscript regarding the information provided to participants about the experiment.

Please address potential limitations arising from participants' reports aligning with researchers' expectations or from participants' beliefs that swimming immediately after eating causes adverse events.

Additionally, please clarify whether the analyses were conducted within subjects; for example, were the data from both sequences combined and then intervention and control conditions were compared.

I am curious why a mood scale for adolescents was applied if the participants were adults.

Finally, I question whether the median swimming time of only 17 seconds was a limitation and whether longer swimming times would contribute to adverse events.

Is the work clearly and accurately presented and does it cite the current literature?

Partly
Is the study design appropriate and is the work technically sound?

Partly
Are sufficient details of methods and analysis provided to allow replication by others?

Partly
If applicable, is the statistical analysis and its interpretation appropriate?

Partly
Are all the source data underlying the results available to ensure full reproducibility?

Yes
Are the conclusions drawn adequately supported by the results?

Partly

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Psychology; Nutrition; Behaviour change; Experimental research

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

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[1] 1. Chambers P, Quan L, Wernicke P, et al.: American red cross scientific advisory committee scientific review: eating before swimming. Int. J. Aquat. Res. Educ. 2011; 5: 483–492. Publisher Full Text

[2] 2. World Health Organization: Drowning.[Cited 2022 Sept 18]. Reference Source

[3] 3. Bartholdy K, Hoff A: 100 myter om sundhed og sygdom. 1st ed.Denmark: FADL; 2015.

[4] 4. Baden-Powell R: Scouting for boys: the original. 1908th ed.United States of America: Dover Publications; 2007.

[5] 5. Britannica: The editors of encyclopaedia Britannica. Is it really dangerous to swim after eating?[Cited 2022 Sept 18]. Reference Source

[6] 6. Jeays AD, Lawford PV, Gillott R, et al.: A framework for the modeling of gut blood flow regulation and postprandial hyperaemia. World J. Gastroenterol. 2007; 13: 1393–1398. PubMed Abstract | Publisher Full Text | Free Full Text

[7] 7. Robertson S, Benardot D, Mountjoy M: Nutritional recommendations for synchronized swimming. Int. J. Sport Nutr. Exerc. Metab. 2014; 24: 404–413. PubMed Abstract | Publisher Full Text

[8] 8. Dwan K, Li T, Altman DG, et al.: CONSORT 2010 statement: extension to randomised crossover trials. BMJ. 2019; 366: l4378. 31. Publisher Full Text

[9] 9. Terry PC, Lane AM, Lane HJ, et al.: Development and validation of a mood measure for adolescents. J. Sports Sci. 1999; 17: 861–872. Publisher Full Text

[10] 10. Terry PC, Lane AM, Fogarty GJ: Construct validity of the profile of mood states – adolescents for use with adults. Psychol. Sport Exerc. 2003; 4: 125–139. Publisher Full Text

[11] 11. Nunes RSM, Freitas AFL, Vieira E: The influence of time of day on the performance of adolescent swimmers. Chronobiol. Int. 2021; 38: 1177–1185. PubMed Abstract | Publisher Full Text

[12] 12. Harmankaya S, Öberg S, Ryg J, et al.: To swim or not to swim after eating: a randomized controlled crossover feasibility trial. [Data set]. Zenodo. 2023. Publisher Full Text

To swim or not to swim after eating: a randomised controlled crossover feasibility trial

Abstract

Background

Methods

Results

Conclusions

Clinicaltrials.gov registration

Keywords

Introduction

Materials and methods

Participants

Setting

Intervention

Figure 1. Illustration of each step of the first and second day of the trial.

User involvement

Outcomes

Randomisation

Statistical methods

Ethical approval

Results

Figure 2. A flow diagram depicting the number of participants who were randomly assigned to 0 minutes or 30 minutes the first trial day, who received the allocated sequence the second trial day, and who were analysed for the outcomes.

Table 1. Participant characteristics and vital signs at baseline.

Adverse events

Visual Analogue Scale of discomfort

Table 2. Overall reported results of swimming immediately and 30 minutes after having lunch.

Profile of Mood States – Adolescents

Swimming time and pulse rate

Discussion

Conclusions

Data availability

Underlying data

Reporting guidelines

References

Comments on this article Comments (0)

Open Peer Review

Comments on this article Comments (0)

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