Exploration of Exercise-Induced Gastrointestinal Syndrome in Endurance-Trained Adolescents: Is There Cause for Concern in Regard to Ultra-endurance Event Participation

Exercise-induced gastrointestinal syndrome (EIGS) in response to prolonged exercise is well-established in adult athletes but no study has investigated how EIGS presents in adolescent athletes despite an increase in youth participation in ultramarathon events. This study aimed to determine the impact of prolonged exercise on gastrointestinal integrity, functional responses, systemic immune profile, and gastrointestinal symptoms (GIS) in youth (YOUTH) vs adult (ADULTS) athletes. Twelve youth (≤ 18y) and twelve adults (≥ 30–50y) completed 3 h treadmill running at 60% V̇O2max (22.9˚C ambient temperature), followed by 2 h seated recovery. Venous and finger-prick blood samples were collected pre-, during-, post-exercise, and during recovery to determine leukocyte counts, plasma concentrations of cortisol, E.coli lipopolysaccharide-stimulated elastase, I-FABP, sCD14, TNF-α and IL-10. Functional gastrointestinal response [i.e., orocecal transit time (OCTT)], GIS [via modified visual analogue scale (mVAS) quantifying self-reported GIS], feeding tolerance and physiological strain variables were assessed pre-, during-, and in recovery from exercise. There was no difference in pre-to-post-exercise concentrations of plasma cortisol, elastase, I-FABP, sCD14, TNF-α, or IL-10 between YOUTH and ADULTS (p > 0.05). YOUTH had higher total leukocyte and neutrophil counts (p < 0.05) in response to exercise [mean (95% CI) 13.1 (10.6 to 15.5) × 109/L, and 8.9 (7.0 to 10.8) × 109/L, respectively] vs ADULTS [9.4 (7.6 to 11.2) × 109/L, and 6.4 (5.0 to 7.7) × 109/L, respectively]. ADULTS reported higher (p = 0.024) upper-GIS severity during exercise [summative accumulation (range of GIS): 252 (6–67)] compared with YOUTH [96 (4–19)]. No other differences were observed in exercise-associated gastrointestinal symptoms (Ex-GIS) or OCTT between groups. The pathways of EIGS in response to exercise do not substantially differ in youth vs adult athletes. Therefore, EIGS and Ex-GIS management strategies for adult athletes are likely transferable to youth athletes. Further studies investigating the use of these specific strategies in youth athletes are required to confirm this.