Exploring the gut-exercise link: A systematic review of gastrointestinal disorders in physical activity

Table 1 Factors affecting the prevalence of gastrointestinal symptoms in exercise

Category	Factor	Description	Impact on GI symptoms	Examples
Physiological	Exercise intensity	High intensity reduces splanchnic blood flow, increasing GI ischemia and permeability	Nausea, vomiting, diarrhea, cramping, and GI bleeding	HIIT, marathon running
	Exercise duration	Prolonged exertion amplifies GI stress via dehydration and fatigue	Abdominal pain, bloating, and diarrhea	Ultra-marathons, triathlons
	Type of exercise	High-impact activities worsen mechanical GI stress	Increased symptoms in running vs swimming or cycling	Running (high risk), swimming (lower risk)
	Hydration status	Dehydration impairs gastric emptying and reduces perfusion	Nausea, cramps, and diarrhea	Inadequate fluid intake during long events
	Training status	Conditioning alters physiological adaptation to GI stress	Beginners, more bloating; elites, risk ischemic symptoms	Novice runners vs elite athletes
	Age and gender	Hormonal and neurochemical factors may increase symptom sensitivity	Females and younger individuals show higher GI symptom prevalence	Female endurance athletes, adolescent runners
Nutrition and hydration	Hydration status	Dehydration impairs gastric emptying and reduces perfusion	Nausea, cramps, and diarrhea	Inadequate fluid intake during long events
	Pre-exercise meal timing	Consuming meals or drinks close to exercise can lead to GI discomfort due to delayed digestion	Increased risk of bloating, cramping, and nausea	Eating a large meal 30 minutes before exercise
	Supplement use	Protein and carbohydrate supplements can cause GI distress, especially when consumed in large amounts	Diarrhea, bloating, and cramping are associated with supplement overuse	Excessive use of protein powders or carbohydrate gels

GI: Gastrointestinal; HIIT: High-intensity interval training.