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1 min read Feb 20, 2026

The Complete Guide to Race Day Energy Gel Fueling

PacePlan
PacePlan Last updated Apr 05, 2026
The Complete Guide to Race Day Energy Gel Fueling

Why Do You Need Energy Gels?

During a marathon, your body burns approximately 2,500-3,000 kcal, but your glycogen stores only hold about 1,500-2,000 kcal. Without bridging this gap, you'll hit the dreaded "bonk" in the second half.

Energy gels deliver 25-30g of fast-acting carbohydrates in the most convenient, efficient form available.

Fueling Timing Guide

When Recommended Action
30 min before start 1 gel + 200ml water
10km mark 1 gel + water
20km mark 1 gel + water or sports drink
30km mark 1 gel + electrolytes
35km mark 1 caffeinated gel (optional)

Key principle: Drink before you're thirsty, fuel before you're hungry.

How to Choose an Energy Gel

1. Carbohydrate Type

  • Maltodextrin only: Fast absorption, but can cause GI distress
  • Maltodextrin + Fructose (2:1 ratio): Up to 90g/hour absorption, reduced GI issues

2. Caffeine Content

  • Use caffeinated gels only once in the second half (after 30km)
  • Typically 25-50mg of caffeine
  • Always test during training first

3. Consistency and Taste

  • Thin/liquid gels: No water needed (e.g., Maurten)
  • Thick gels: Must take with water (e.g., GU, PowerGel)
Brand Carbs Caffeine Notes
Maurten Gel 100 25g None Hydrogel technology, minimal GI stress
GU Energy 22g 0-40mg Wide flavor range, great value
SiS GO 22g 0-75mg Thin consistency, no water needed
PowerBar PowerGel 27g 0-50mg High carb content

Always Test in Training

Never try a new gel on race day. Practice your exact fueling strategy during at least 3-4 long runs.

Test Checklist

  • [ ] No GI discomfort
  • [ ] Noticeable energy boost after intake
  • [ ] Timing aligned with aid station locations
  • [ ] Practice opening gel packets (especially with gloves)

Race Day Pro Tips

  1. Pre-load 4-5 gels in your belt or shorts pocket
  2. Take gel 200m before an aid station → Chase with water at the station
  3. Never combine energy drinks with gels — double fructose can cause stomach cramps
  4. In hot/humid conditions, bring extra electrolyte tabs

PacePlan reports include a personalized fueling strategy based on your body type, goal time, and gel preference.

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This content is for informational purposes and is not a substitute for professional medical advice.

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Frequently Asked Questions

How many miles per week do I need for a sub-4 marathon?
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Most sub-4 plans require 25-45 miles per week depending on the methodology. Pfitzinger recommends 30-45 miles, Hanson plans peak at 35-40, and Daniels-based plans can reach 40-50. Quality matters as much as volume — include one tempo run and one interval session alongside your easy miles.
Can I do this plan in 6 weeks instead of 8?
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While it is possible to compress the plan, we strongly recommend the full 8 weeks. Proper physiological adaptation takes time, and rushing increases injury risk — especially if you haven't been maintaining a high base mileage consistently.
What if I miss a long run?
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Don't try to make it up by cramming it into a rest day. Simply move on to the next scheduled workout. Missing one run won't derail your training, but overtraining to compensate might cause injury.
Should I run negative splits in a marathon?
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Yes. Research shows that running the second half faster leads to faster finish times. Start conservatively at 5:45-5:50/km (9:15-9:25/mi) and build to 5:30-5:35/km (8:50-9:00/mi) in the second half. Runners who pace evenly or negatively are 45% more likely to hit their goal time.
How important is tapering before a marathon?
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Critical. A 2-3 week taper reduces training volume by 40-60% while maintaining intensity, allowing muscle glycogen stores to fully replenish. Studies show proper tapering improves performance by 2-3%. You'll feel restless — that's normal. Trust the science.
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