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2023-05-15 09:17| 来源: 网络整理| 查看: 265

ORIGINAL RESEARCH article Front. Nutr., 12 April 2023Sec. Sport and Exercise Nutrition Volume 10 - 2023 | https://doi.org/10.3389/fnut.2023.1133022 Carbohydrate knowledge, beliefs, and intended practices, of endurance athletes who report exercise-associated gastrointestinal symptoms

Rachel Scrivin1,2*,

Ricardo J. S. Costa3,

Fiona Pelly1,

Dana Lis4 and

Gary Slater1 1School of Health and Behavioural Sciences, University of the Sunshine Coast, Sippy Downs, QLD, Australia 2Faculty of Health, Education and Environment, Te Pukenga, New Zealand Institute of Skills and Technology, Tauranga, New Zealand 3Department of Nutrition Dietetics and Food, Monash University, Melbourne, VIC, Australia 4Department of Neurobiology, Physiology and Behaviour, University of California, Davis, CA, United States

This study aimed to explore carbohydrate (CHO) knowledge, beliefs, and intended practices of endurance athletes who experience exercise-associated gastrointestinal symptoms (Ex-GIS) compared to those without Ex-GIS. A validated online questionnaire was completed by endurance athletes (n = 201) participating in >60 min of exercise that present with Ex-GIS (n = 137) or without (n = 64). Descriptive statistics were used for parametric and non-parametric data with appropriate significance tests. Associations between categorical data were assessed by Chi-square analysis, and post-hoc Bonferroni tests were applied when significant. A content analysis of open-ended responses was grouped into themes, and quantitative statistics were applied. Participants included runners (n = 114, 57%), triathletes (n = 43, 21%) and non-running sports (n = 44, 21%) who participate in recreational competitive (n = 74, 37%), recreational non-competitive (n = 64, 32%), or competitive regional, national, or international levels (n = 63, 31%). Athletes correctly categorized CHO (x̄ = 92–95%) and non-CHO (x̄ = 88–90%) food and drink sources. On a Likert scale of 1 (strongly disagree) to 5 (strongly agree) athletes typically agree or strongly agree that consuming CHO around key training sessions and competitions enhances athletic performance [median = 4 (IQR, 4–5)], and they intend to consume more CHO around exercise [median = 3 (IQR, 2–3)]. No differences in beliefs and intentions were found among athletes with or without Ex-GIS. To enhance athletic performance, most endurance athletes intend to consume more CHO around exercise. Adequate knowledge of CHO-containing food sources was apparent; however, specific CHO ingestion practices remain to be verified.

Introduction

Endurance athletes frequently report developing gastrointestinal symptoms around exercise, e.g., bloating, urge to defecate, burping, regurgitation, and diarrhea, referred to as exercise-associated gastrointestinal symptoms (Ex-GIS) (1–3). Ex-GIS develop through the gastrointestinal circulatory or neuro-endocrine pathways or via mechanical strain on the peritoneal cavity (2, 4). A description of Ex-GIS has been defined within the exercise-induced gastrointestinal syndrome model, outlining the complex pathophysiology involved in the development of Ex-GIS (5, 6). Many endurance athletes who report Ex-GIS implement strategies to manage symptomology (7–9), including reducing CHO-rich foods such as bread, cereals, milk, and yoghurt (7). Therefore, endurance athletes with Ex-GIS may be modifying their dietary intake to reduce Ex-GIS development, perhaps at the expense of their CHO intake. Given the critical role carbohydrates play as a substrate during exercise to support performance enhancement (10, 11), carbohydrate intake guidelines have been established for athletes, including total daily targets, plus specific guidance before, during, and after exercise (12, 13).

Endurance athletes typically train for >60 min several times a week. However, the recommended CHO intake ranges vary depending on the duration and intensity of exercise (12, 13). An individualized approach is recommended for CHO consumption, however as a general guideline of 3 g.kg−1.d−1 CHO for low-intensity or skill-based training, up to 8–10 g.kg−1.d−1 CHO for moderate to high-intensity or sustained exercise (12, 13). For key training sessions or competitions, 10–12 g.kg−1.d−1 CHO, 24–36 h before sustained endurance events, is associated with improved performance (12, 13). During endurance exercise lasting 1–3 h, it is recommended that athletes consume 30–60 g.h−1 CHO (12, 13). More extended endurance activities lasting >3 h, 90 g.h−1 CHO from multiple transportable CHO sources (i.e., glucose and fructose in a ratio of 2:1) to increase CHO availability and CHO oxidation efficiency, thereby reducing fatigue and improving athletic performance (12, 13). Despite these recommendations, many endurance athletes do not meet daily CHO targets leading up to competition (14) or during endurance events (3, 15, 16), possibly due to a lack of practicing with race day nutrition or experimenting with food and fluid quantities to determine feeding tolerance and preferences (17). Individuals who experience Ex-GIS may be more susceptible to not achieving CHO intake targets due to varied dietary strategies implemented to reduce symptomology (7–9).

Interestingly, athletes that present with Ex-GIS may benefit from the ingestion of CHO during exercise, as this strategy has been shown to reduce the development and severity of Ex-GIS and mitigate disruptions to the integrity of the intestinal epithelium (2, 18–22). CHO consumed during exercise increases portal vein blood supply, enhancing blood flow to the splanchnic region (23). This likely increases intestinal epithelial blood flow, thereby reducing intestinal injury and the subsequent development of gastrointestinal complications (18, 19). However, ingestion of CHO above an individual’s tolerance level may exacerbate Ex-GIS, irrespective of exercise duration or intensity (24).

This exploratory study investigates the CHO knowledge, beliefs, and intended practices of endurance athletes who report Ex-GIS. Due to the complex pathophysiology of the development of Ex-GIS, it is hypothesized that endurance athletes who experience Ex-GIS may have beliefs and intentions about CHO consumption that varies from sports nutrition guidelines or recommendations (10, 12, 13).

Methods Participants

This exploratory study applied a validated online questionnaire investigating endurance athletes who report Ex-GIS and their CHO knowledge, beliefs, and intended practices (25) (Supplementary file 1), compared to a subgroup of athletes without Ex-GIS. Convenience sampling was used for athlete recruitment given researchers had associations with endurance athlete groups or professional contacts who support endurance athletes. Endurance athletes ≥18 years (y) of age, participating in endurance events ≥60 minutes (min), were invited to participate in the study. Only questions related to CHO knowledge, beliefs, intended practices and sports nutrition strategies were included in this study. Specific questions regarding nutritional strategies for managing Ex-GIS, including the use of nutritional supplements were excluded, as this has been previously reported (26).

This study was approved by the Human Research Ethics Committee (University of the Sunshine Coast, Australia), ethics approval number S201402 and conducted in accordance with the Declaration of Helsinki for human research. Athletes accessed the questionnaire online through Qualtrics Core XM survey platform (RRID:SCR_016728) (Qualtrics LLC, 333 West River Park Drive, Provo, UT 84604, United States). Athletes were required to provide written informed consent and all data collected was anonymous. Demographic data collected included biological sex and age. Other information collected included main sport, participation level, and event characteristics (single-day or multi-day).

Questionnaire

Using a dichotomous scale, 15 food and drink options were categorized as CHO or non-CHO food or drink sources to determine athletes CHO knowledge. Athletes rated their beliefs about consuming CHO for enhancing athletic performance at various time points around exercise on a Likert scale from 1 (strongly disagree) to 5 (strongly agree). The time points assessed were 1–2 days before events lasting ≥90 min, in the last meal or snack before endurance training or events lasting ≥90 min, during endurance exercise or an event lasting ≥60 min, and within 30 min after endurance exercise when there is 3 h (1, 15, 16, 32).

It is likely that to improve gastrointestinal tolerance (i.e., less Ex-GIS development) when consuming CHO during exercise, athletes may require a period of gut training (19, 20, 24). Studies implementing a gut-training protocol have shown less reported Ex-GIS and improved performance times (19, 20). Therefore, in an athlete’s nutritional plan, a period of gut training may be warranted to reduce Ex-GIS development during exercise and benefit from higher CHO oxidation rates due to greater exogenous CHO availability (19, 20).

The current study did not investigate the quantification of CHO intake among endurance athletes with Ex-GIS. Athletes have indicated they intend to increase their CHO intake around exercise to enhance performance. However, it is still unknown if they meet the recommended CHO targets for endurance training and recovery; as previous research indicates that many endurance athletes without pre-existing Ex-GIS are not meeting the recommended CHO targets (1, 15, 16, 33). This information would be valuable for practitioners when providing nutrition education and meal planning around CHO intakes to support athletic performance.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethics statement

The studies involving human participants were reviewed and approved by Human Research Ethics Committee (University of the Sunshine Coast, Australia), ethics approval number S201402. The patients/participants provided their written informed consent to participate in this study.

Author contributions

RS and GS: conceptualization and writing—original draft. RS, GS, RC, FP, and DL: methodology and writing—review and editing. RS: validation, formal analysis, investigation, and project administration. GS: supervision. All authors contributed to the article and approved the submitted version.

Funding

The work was supported by the University of the Sunshine Coast, Australia.

Acknowledgments

It is acknowledged that RS has received an Australian Government Research Training Program Scholarship for her research studies.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fnut.2023.1133022/full#supplementary-material

References

1. Pfeiffer, B, Stellingwerff, T, Hodgson, AB, Randell, R, Pottgen, K, Res, P, et al. Nutritional intake and gastrointestinal problems during competitive endurance events. Med Sci Sports Exerc. (2012) 44:344–1. doi: 10.1249/MSS.0b013e31822dc809