Gastric emptying: the rate at which the stomach empties
IntensityRate at which stomach contents pass into the intestine, a key factor of nutrition tolerance in long-distance racing.
Gastric emptying regulates the rate at which food and drink pass from the stomach to the intestine where they will be absorbed. At rest, this rate is around 500-800 ml/hour for isotonic fluid. In racing, it drops with intensity (blood flow diverted to muscles) and becomes one of the main limitations to energy intake. Blocked emptying (exercise-induced gastroparesis) shows up as nausea, heaviness, bloating, sometimes vomiting. Factors that speed it up: liquid rather than solid, carb concentration under 8%, drink temperature close to body, moderate intensity. Factors that block it: concentration over 8%, very cold drinks, intensity above threshold, dehydration.
In TriPaced:
TriPaced recommends testing your nutrition strategy in long sessions with target concentration (often 6-7% carbs) and planned intensity. If emptying blocks in training, it will also block in the race: better to discover it in a long session than 90 min into the Ironman bike. The tip 'Nutrition failure in race: plan B at aid station' provides the gastric reset protocol.
Source Costa RJS et al., 2017: Systematic review: exercise-induced gastrointestinal syndrome, Alimentary Pharmacology & Therapeutics