Objectives: This study aimed to determine the impact of running and cycling exercise modalities on the magnitude of exercise-induced gastrointestinal syndrome (EIGS) and associated gastrointestinal symptoms (GIS).
Design: Parallel group trial design.
Methods: Twenty-eight endurance athletes (male n = 14, female n = 14) completed 2 h running at 55 % of maximal oxygen uptake or cycling at 55 % of maximal aerobic power in Tamb 35 °C and 22 % RH. Pre- and post-exercise blood samples were collected and analysed for markers of intestinal epithelial integrity perturbations (i.e., plasma intestinal fatty acid protein (I-FABP), soluble (s)CD14, and lipopolysaccharide binding protein (LBP)) and systemic inflammatory cytokines (i.e., plasma IL-1β, TNFα, IL-10, and IL-1ra). GIS were assessed pre-exercise and every 10 min during exercise.
Results: Exercise-associated Δ for plasma I-FABP (191 and 434 pg‧ml-1) and LBP (-1228 and 315 ng‧ml-1) did not differ between running and cycling, respectively; however for sCD14 was higher (p = 0.030) on cycling (116 ng‧ml-1) vs running (96 ng‧ml-1). There were no differences in absolute pre- and post-exercise systemic inflammatory cytokine concentration, with large individual variation observed. Exercise-associated plasma TNF-α, (p = 0.041) and IL-10 (p = 0.019) responses were greater in running than cycling, but did not lead to a greater systemic inflammatory response profile (p = 0.305) between running (5.0arb.units) and cycling (-2.5arb.units). Although greater GIS incidence occurred in running (44 %) compared with cycling (25 %), there was no difference between groups for GIS severity.
Conclusions: When running and cycling exercise is performed with similar duration, intensity, ambient conditions, and with confounder control, the exercise modality does not substantially impact the magnitude of EIGS or associated GIS severity.
Keywords: Cycling; Cytokines; Endotoxin; Exertional-heat stress; Intestinal epithelium; Running.
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