Does exertional heat stress impact gastrointestinal function and symptoms?

Area of Science:

• Exercise Physiology
• Gastroenterology
• Thermoregulation

Background:

• Exertional-heat stress poses significant thermoregulatory challenges, potentially impacting splanchnic circulation and sympathetic nervous system activity.
• The precise effects of exertional-heat stress on gastrointestinal function, including gastric motility and transit, remain incompletely understood.

Purpose of the Study:

• To investigate the impact of exertional-heat stress on gastric myoelectrical activity.
• To determine the effects on orocecal transit time (OCTT).
• To assess the influence on gastrointestinal symptoms (GIS) in endurance runners.

Main Methods:

• A randomized cross-over study involving 16 endurance runners.
• Participants completed 2 hours of running at 60% VO2max in hot (35°C) and temperate (22°C) conditions.
• Gastric myoelectrical activity (cEGG), OCTT (lactulose challenge), and GIS were measured pre- and post-exercise.

Main Results:

• Higher post-exercise core temperatures were observed in hot conditions compared to temperate.
• Gastric myoelectrical activity showed reduced normal frequency and increased bradygastria in both conditions, with greater severity in hot conditions.
• Orocecal transit time was significantly slowed in both conditions, with no difference between hot and temperate trials. Gastrointestinal symptom incidence and severity were notably higher in the hot condition.

Conclusions:

• Running in both hot and temperate conditions induces alterations in gastric myoelectrical activity and orocecal transit time.
• Exertional-heat stress specifically exacerbates gastrointestinal symptoms, increasing both their incidence and severity compared to temperate conditions.