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Calculate your baseline requirements for carbohydrates, sodium, and fluid per hour. Based on current sports nutrition guidelines for endurance athletes.
Your target fueling rate depends directly on your body weight, event duration, and target exercise intensity. Longer workouts and races demand higher carbohydrates per hour to prevent glycogen depletion, while your body weight dictates your baseline fluid and sodium requirements.
During prolonged endurance exercise, your muscle glycogen stores are limited. Consuming exogenous carbohydrates preserves these glycogen reserves, maintaining power output and delaying fatigue.
Historically, 60g/hr of glucose was considered the absolute absorption limit. However, by combining glucose with fructose (typically in a 2:1 or 1:0.8 ratio), you utilize different intestinal transporters (SGLT1 for glucose and GLUT5 for fructose). This dual-source approach allows athletes to safely absorb 90g or even 120g of carbohydrates per hour without gastrointestinal distress.
When running a 100-mile ultra-marathon or cycling a 300km+ brevet, "bonking" (depleting liver and muscle glycogen) is a primary reason for DNF. Exogenous fueling is not just about performance—it is about survival. Keeping carbs high prevents systemic energy crashes and supports gut motility over long multi-hour efforts.
Cycling fueling is typically measured in grams of carbohydrates rather than raw calories. A standard target is 60–90 grams of carbohydrates per hour (equivalent to 240–360 calories). For shorter or easier sessions, 30–60g is sufficient, while competitive racers and ultra-distance athletes may scale up to 100–120g/hr.
Most athletes lose between 500mg and 1,500mg of sodium per liter of sweat. A safe baseline for a standard nutrition plan is 500–1,000mg of sodium per liter of fluid. For hot weather or heavy sweaters, this should be scaled up to prevent hyponatremia and muscle cramping.
Liquid carbs (gels, drink mixes) are absorbed faster because they require minimal digestion. They are ideal for high-intensity efforts. Solid foods (bars, chews, real food) are better suited for lower-intensity, long-duration rides or ultra-runs where gut comfort and flavor fatigue become major factors.