Ultra-endurance

Ultra‑endurance events last at least six hours and typically involve running, cycling or multi‑sport races over long distances. These competitions place extreme demands on energy stores and fluid balance, often resulting in a substantial energy deficit and a 2–5% body‑water loss if hydration is not managed.

Fuel and hydration considerations

Athletes tackling ultra‑distance races need to sustain energy intake for many hours. Research indicates that carbohydrate intakes around 90 g per hour are recommended for ultra‑trail activities lasting more than 2½ hours, and intakes up to 120 g/h may help to limit neuromuscular fatigue. The International Society of Sports Nutrition notes that runners should aim for 150–400 kcal per hour, supplied by about 30–50 g/h of carbohydrate and 5‑10 g/h of protein, using a mix of palatable, calorie‑dense foods. Because ultra‑distance races span many hours, a glucose‑to‑fructose blend can improve carbohydrate oxidation and reduce gastrointestinal distress. Maintaining hydration is equally important. Guidelines suggest consuming 450–750 mL of fluid per hour—roughly 150–250 mL every 20 minutes—together with sodium concentrations higher than 575 mg/L to reduce the risk of exercise‑associated hyponatremia. Planned drinking is necessary for long events and high sweat rates; athletes should avoid drinking so much that body mass is gained. Hydration strategies should be adjusted for temperature and altitude.

Fueling in practice

During a 100 km ultra‑marathon lasting around 10 hours, a runner might consume a mix of gels, fruit or rice cakes to deliver 30–50 g of carbohydrate per hour while sipping 150–250 mL of fluid every 20 minutes and adding sodium tablets to meet electrolyte needs. A 24‑hour cycling event participant may use a carbohydrate drink that supplies around 90 g/h from glucose and fructose along with small portions of sandwiches or potatoes for savoury calories. Because thirst is not always a reliable indicator of fluid needs, athletes weigh themselves during long stops to avoid both dehydration and over‑hydration, aiming to keep body mass loss within a few percent. Some competitors practise “gut training,” gradually increasing carbohydrate intake during training to improve tolerance to high hourly intakes.

After the event, recovery nutrition should begin quickly; rehydration with sodium‑rich fluids and a balanced meal helps replace fluids and restore muscle glycogen.

Ultra‑endurance competitions demand careful planning, but by following evidence‑based guidelines for carbohydrate intake, protein, sodium and fluid, athletes can reduce fatigue and maintain performance through very long races.

Related Terms: Endurance event, Recovery window, Hot‑humid conditions, Altitude training, Per‑serving carbohydrate