By Performance Nutritionist, Tamara Walker book a 1-2-1 with Tam here

Many young runners experience gastrointestinal distress (GI) during training and races. Gastrointestinal distress includes stomach cramps, nausea, gas, diarrhoea, or urgency to use the bathroom. These problems can make running uncomfortable, affect performance, and sometimes discourage young athletes from training consistently. Understanding why GI happens, how to prevent it, and when to seek help can make a big difference for both athletes and parents. 

Why Gastrointestinal Distress Happens in Running?

Running is strongly linked with gastrointestinal symptoms for several reasons. Each factor affects the digestive system in a unique way.

 

1. Changes in Gut Blood Flow

During running, blood is redirected from the digestive system to the muscles that are working hardest. This reduced blood flow can slow digestion, making the stomach feel heavy or crampy. Intestinal permeability, sometimes called “leaky gut,” can increase under these conditions, allowing small amounts of undigested food or toxins to cross the gut lining. This temporary change can trigger stomach discomfort, bloating, or nausea [1]. Young runners may notice these effects more during intense training or long-distance runs.

 

2. Repetitive Motion and Impact

The repetitive up-and-down motion of running causes the organs in the abdomen to move with every stride. This jostling can irritate the gut and lead to cramping, nausea, or diarrhoea. Longer runs or high-intensity sprints tend to make these symptoms worse. Research suggests that the more experienced runners become, the better they often tolerate this impact, which is why practice and gradual training are important [1,2].

 

3. Food and Drink Choices

What and when a young runner eats can greatly affect gastrointestinal comfort. Heavy meals, foods high in fat or fibre, or large amounts of sugar before a run can slow digestion and trigger stomach upset. On the other hand, simple snacks like a banana, toast, or a small bowl of porridge eaten 30–60 minutes before running are usually well tolerated. Sports drinks and gels can be helpful for long runs, but overconsumption or using them for the first time during a race may worsen symptoms [2,3].

 

4. Gut Adaptation and Intestinal Function

The digestive system can adapt over time to the stress of running. Intense or prolonged exercise temporarily increases intestinal permeability, meaning the gut lining becomes more permeable. While this is usually harmless, it can make the gut more sensitive to food, fluids, or stress. Gradually increasing training distance and intensity allows the gut to adapt, reducing the likelihood of stomach upset during races [1,4].

 

5. Heat and Environmental Stress

Running in hot or humid conditions adds stress to the body and digestive system. Heat increases core body temperature, which may amplify gut permeability and reduce comfort. Young runners may notice more cramping, bloating, or diarrhoea on hot days. Adjusting training intensity, staying well-hydrated, and planning runs during cooler parts of the day can help reduce these issues [4].

 

6. Stress and Anxiety

Mental stress, including pre-race nerves or performance anxiety, can influence gut function. Stress can increase gut motility (the speed at which food moves through the digestive tract), trigger cramping, or cause urgency. Teaching young athletes calming routines, deep breathing, or visualisation techniques before runs can help reduce stress-related gastrointestinal symptoms [2].

 

What Are The Signs to Watch For in Runners?

Young athletes may experience:

·      Stomach cramps

·      Nausea or vomiting

·      Bloating or gas

·      Diarrhoea

·      Discomfort after eating

Symptoms may occur before, during, or after training and can vary depending on intensity, nutrition, and environmental conditions.

 

How to Prevent Gastrointestinal Distress in Running?

 

1. Plan Meals and Snacks Carefully

Time meals to allow digestion: larger meals 2–3 hours before running, and small, easily digested snacks 30–60 minutes prior. Avoid high-fat or high-fibre foods before runs. Encourage athletes to test different foods during training rather than on race day to identify what works best [2,3].

 

2. Maintain Proper Hydration

Drink small, regular amounts of fluid rather than large quantities all at once. Dehydration and overhydration can both trigger gastrointestinal upset. For longer runs, practice drinking water or low-concentration electrolyte drinks gradually so the gut can tolerate it [2,5].

 

3. Introduce Nutrition During Training

During longer runs, gradually introduce carbohydrate or electrolyte solutions to help the gut adjust. Practice helps reduce cramping or nausea during races and improves performance. Avoid introducing new foods or drinks for the first time on race day [5].

 

4. Build Gut Tolerance Over Time

Start with shorter runs and gradually increase distance and intensity. Over time, the gut adapts to stress, reducing the likelihood of cramping or diarrhoea. Include practice runs under different conditions, such as warmer weather or varying terrain, to help the gut adjust [1,4].

 

5. Reduce Stress and Anxiety

Pre-run routines, deep breathing, or visualisation can calm nerves. Keeping training enjoyable and avoiding last-minute changes in routines can also reduce stress-related stomach discomfort [2].

 

6. Adjust for Environmental Factors

During hot or humid days, slow the pace, hydrate more often, and consider shorter or less intense runs. Running at cooler times of day can help the digestive system cope better with environmental stress [4].

 

When to Seek Medical Advice?

Contact a healthcare professional if a child:

·      Experiences persistent or severe stomach pain

·      Has vomiting or diarrhoea lasting more than one day

·      Shows signs of dehydration such as dark urine or dizziness

·      Loses weight or regularly misses training because of GI issues

Persistent problems may indicate food sensitivities like lactose intolerance or other conditions requiring evaluation.

 

Why This Matters for Runners?

Gastrointestinal distress is common but manageable. Even mild symptoms can impact training quality and enjoyment. Understanding the causes, practising prevention strategies, and gradually building tolerance helps young runners stay healthy, confident, and comfortable during training and competition.

 

Key Takeaways

·      GI distress in running can result from reduced blood flow, repetitive motion, food choices, environmental stress, or anxiety.

·      Gradual training, careful meal timing, hydration, and nutrition practice can reduce symptoms.

·      Severe or persistent issues should be evaluated by a healthcare professional.

By Performance Nutritionist, Tamara Walker book a 1-2-1 with Tam here

Disclaimer: This article is intended to provide general information about nutrition for youth athletes and is not meant to replace professional dietary advice or individual nutritional counselling. Every child's nutritional needs can vary due to factors such as age, size, physical activity level, and medical conditions. We strongly recommend consulting with a registered dietitian or a healthcare provider before making changes to your child's diet, such as adding food powders. YSN and the author of this article do not take responsibility for any possible consequences from any treatment, procedure, dietary modification, action, or application of medication which results from reading or following the information contained in this article.

References

1.        Karhu E, Forsgård RA, Alanko L, et al. Running for 90 min at a challenging pace increases intestinal permeability and serum markers of gut function but does not correlate with gastrointestinal symptoms in runners. European Journal of Applied Physiology. 2017;117(10):2347‑2354. https://link.springer.com/article/10.1007/s00421-017-3739-1

2.        Ter Steege RW, Kolkman JJ. Dietary restrictions and gastrointestinal symptoms in endurance runners: how runners try to reduce exercise‑induced gut problems. Journal of the International Society of Sports Nutrition. 2020;17:32. https://pubmed.ncbi.nlm.nih.gov/32522222/

3.        Development of a questionnaire to assess dietary choices runners use to reduce GI symptoms. Journal of the International Society of Sports Nutrition. 2019. https://jissn.biomedcentral.com/articles/10.1186/s12970-019-0278-7

4.        Dietary intake and gastrointestinal integrity in runners undertaking high intensity exercise in heat conditions. PubMed. 2021;340(30124). https://pubmed.ncbi.nlm.nih.gov/34030124/

5.        Martinez IG, Mika AS, Biesiekierski JR, Costa RJS. The effect of gut training and feeding challenge on gastrointestinal status in response to endurance exercise: systematic review. Sports Medicine. 2023. https://pubmed.ncbi.nlm.nih.gov/37061651/