Hydration / Sodium / Endurance Fueling
A simple weigh-before/weigh-after method for estimating sweat rate. This guide is written for cyclists first, with notes that also apply to runners and triathletes when the same endurance-fueling principles carry over.
Good fueling is not about chasing a perfect number for its own sake. The goal is to deliver enough carbohydrate, fluid, and sodium for the session you are actually doing, using products and foods you can tolerate when the effort gets real.
Start with conditions, not a fixed rule
- Weigh before and after a representative workout.
- Account for fluid consumed and bathroom stops as best you can.
- Convert the difference into approximate fluid loss per hour.
Do not separate fuel from hydration
Carbohydrate, water, and sodium solve different problems, but they interact during real rides. A carb-heavy bottle might help energy intake, while plain water or electrolyte drink may be needed for thirst and fluid replacement. Sweat rate, weather, indoor cooling, and refill access all change the plan.
Apply this to a BonkGuard race plan
BonkGuard connects editable targets to the products and bottles selected for a race. Planned intake in Overview compares the schedule with carbohydrate, fluid, and optional sodium targets, then expands to race totals including calories, caffeine, potassium, and magnesium.
Schedule answers what to take and when, while Packing summarizes quantities and bottle preparation. The athlete controls the targets and products, can use Practice this plan before the event, and explicitly decides when the plan is Race Ready.
Useful next reads
- Beginner’s Guide to Cycling Nutrition
- Advanced Guide to Cycling Fueling
- How to Avoid Bonking on Long Bike Rides
- Cycling Fueling Calculator: What Inputs Actually Matter?
- Indoor Cycling Fueling: What Changes on the Trainer?
- How to build a complete race-day fueling plan
Key takeaway
Weigh before and after a representative workout. Build the plan around the full session, then keep the execution simple enough to follow when the ride gets hard.
Educational note
This article is educational and is not medical or nutrition-treatment advice. Athletes vary widely in tolerance, sweat rate, health history, and goals. Practice fueling and hydration changes in training, not for the first time on race day, and work with a qualified professional when you need individualized medical or nutrition guidance.