For shorter endurance races — like Olympic and Sprint triathlons or half marathons — you burn a lot more energy than usual. To perform well, you need to fuel smart with carbohydrates, fluids, and electrolytes during the event.
Why Nutritional Planning Matters
During high-intensity endurance events, your body burns energy fast — about four times your normal calorie use. Most of this energy comes from carbohydrates, and your stored carbs (glycogen) begin to run low after about 50–70 minutes, often depleting entirely around 90–120 minutes if not replenished.
Because fat stores are plentiful and slow-burning, the priority during these shorter events is carbohydrate replacement, but also proper hydration and electrolyte balance so you maintain performance and avoid fatigue.
General Guideline for Carbs, Fluids, and Sodium
Most products you use should provide mostly carbohydrates. Study nutrition labels so you know exactly how much carb you’ll get from gels, blocks, or drinks.
Carbohydrate, fluid, and sodium targets during the race:
Notes on Fluids and Salt: Drinking to thirst is usually enough for shorter events, but if you sweat heavily, aim for sports drinks with 500–700 mg sodium per litre. Athletes who lose more salt (“salty sweaters”) may need upwards of 1,000 mg per litre.
For US conversion, use these calculators: grams to US ounces OR kilograms to pounds).
Examples of What This Looks Like in Practice
Sprint Triathlon (~90 min)
Before the swim: optional carb gel (~20 g) before the start
On the bike: water or electrolyte drink as needed
Late bike / transition: another gel or small block toward the end of the bike leg
Continue fluids from run aid stations or your own bottles as needed
Half Marathon (~2 hrs)
Sip a carb drink (e.g., ~80 g carb in a small bottle) on the run
Or take 3–4 gels spaced evenly (e.g., every 20 min) after 50–70 min
Keep sipping water and electrolytes as needed
Olympic Triathlon (~2 hr 45 min)
One carb gel (~20 g) before the start
During the bike: Clif Shot Bloks or similar chews spaced throughout (e.g., 9 blocks ≈ 72 g carbs)
Or use one carb drink (e.g., ~80 g carb) sipped evenly on the bike
Another gel in transition to start the run
Additional gels or aid-station carbohydrates every ~20 minutes as needed
Practice Before Race Day
Experiment with products and timing during training so your gut is used to the calories and fluids you plan to take on race day. What works in training tends to work best under race conditions.
Key Takeaways
Focus on carbohydrates because glycogen stores deplete quickly in high-intensity endurance efforts.
Hydration should be guided by thirst, with attention to sodium if you sweat heavily.
Plan your intake (~30–90 g carbs/hour) depending on event duration and practice it in training.Key Considerations
- Replenishing fluids and electrolytes can prevent dehydration and hyponatremia (when the blood sodium level is below normal).
- Post-race nutrition helps replenish the body, restore muscle, replace fluids and sodium lost to sweat and respiration and provides the nutrients needed for muscle repair.
Further Reading
Check the articles below for more about your nutrition and hydration needs during your event.
Essential Hydration Hacks for Race Day and Beyond (video)
Nutrition and Hydration Logistics
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