Brick Training Nutrition: After Fueling the Bike Leg, Should You Still Fuel the Run?

“You already ate 3 gels on the bike leg—do you still need to fuel on the run?” This is the most common fueling question in Brick training. The answer isn’t “yes” or “no,” but rather depends on the Brick’s duration, intensity, and training goals.

1. Basic Fueling Principles

Three Key Principles of Sports Fueling

1. Carbohydrates: 30–90g per hour (depending on intensity and tolerance)
2. Fluids: 500–750ml per hour
3. Electrolytes: 300–700mg sodium per hour (depending on sweat rate)

The Unique Nature of Brick Training

Brick training isn’t just about building fitness—it’s also about “testing your fueling strategy.” Discovering fueling problems on race day is too late. Brick is the perfect opportunity for fueling experiments.

2. Fueling Strategies for Bricks of Different Durations

Short Brick (30+10, 40 minutes total)

Fueling principle: Eat a light meal 1 hour before training; only take fluids during the session.

Time Period	Fueling Content
60 min before training	1 banana + 240ml water
Bike leg	250ml sports drink
Run leg	No fueling (unless extremely hot)

Purpose: Train the ability to perform under low glycogen without relying on fueling.

Medium Brick (90+30, 2 hours total)

Fueling principle: Similar to racing—fuel on the bike, observe on the run.

Time Period	Fueling Content	Carbs (g)
90 min before training	Oatmeal + eggs + banana	60
Bike 0:30	1 gel + 200ml water	30
Bike 1:00	1 energy bar + 200ml sports drink	40
Bike 1:30	1 gel + 200ml water	30
Run leg	Observe how you feel; no fueling needed within 30 minutes	0–25

Long Brick (4+1, 5 hours total)

Fueling principle: Fully simulate race day.

See the other article “Long Brick Workout Design” for detailed fueling.

3. Criteria for Deciding Whether to Fuel on the Run Leg

Criterion 1: Duration

Run Duration	Fuel or Not	Content
< 30 minutes	No fueling	Water only
30–60 minutes	Depends	Half a gel
60–90 minutes	Fuel	1–2 gels
> 90 minutes	Must fuel	Every 20–25 minutes

Criterion 2: Intensity

• Below Z2: Can rely on fat oxidation; fueling needs are low
• Z3: Carbohydrate expenditure increases; fueling is recommended
• Z4 and above: Purely carbohydrate-fueled; fueling is mandatory

Criterion 3: Training Purpose

Training Purpose	Fueling Strategy
Race simulation	Fuel exactly as on race day
Low-glycogen training	Fuel on bike, no fueling on run
Fueling strategy testing	Try new products
Pure fitness training	Standard fueling

4. Fueling Strategy for the Bike Leg

Why the Bike Leg Is the “Golden Fueling Window”

1. Faster gastric emptying (riding position is less jarring)
2. Stable body temperature (better heat dissipation)
3. No worry about vomiting
4. Can take fluids and carbs simultaneously

Recommended Fueling Schedule (Per Hour)

Time Point	Fueling	Carbs
0:00 (start)	200ml sports drink	15g
0:20	1 gel + 100ml water	30g
0:40	Half a banana / half an energy bar	20g
1:00 (repeat every hour)	—	65g/hr

5. Fueling Strategy for the Run Leg

Why Fueling on the Run Is Difficult

1. Slower gastric emptying: Vertical impact disrupts digestion
2. Blood flow redistribution: Muscle blood flow increases, stomach blood flow decreases
3. Higher body temperature: Increased stomach discomfort
4. Higher breathing rate: Conflicts with chewing and swallowing

Fueling Options for the Run Leg

Fuel Type	Pros	Cons	Recommended Timing
Gel	Easy to swallow, fast absorption	Too sweet, needs water	Every 20–25 minutes
Energy drink	Fuels and hydrates at once	Limited carrying capacity	Every 5 km
Gummies	Good taste, easy to portion	Requires chewing	Mid-run fueling
Salt tablets	Replaces electrolytes	No carbs	Every 30 minutes
Banana	Natural, easy to digest	Hard to carry	Available at aid stations

6. Applying Train Low

Concept

Deliberately training in a low-glycogen state to enhance fat-burning capacity. Brick training is a great opportunity to execute Train Low.

How to Execute

• Reduce carbohydrate intake 12 hours before training
• Train fasted in the morning (water only)
• Hydrate but don’t consume carbs on the bike leg
• No carbs on the run leg either
• Consume a full recovery meal within 30 minutes after training

Cautions

• Intensity must not be too high: Primarily Z1–Z2
• Duration control: Within 90 minutes
• Frequency: At most once per week
• Not recommended for beginners: Hypoglycemia risk if the base isn’t solid

7. Head-to-Head Comparison of Fueling Products

Here’s how common fueling products perform in Brick training:

Gels

Brand	Carbs per serving	Texture	Recommendation
GU Energy	22g	On the sweet side	★★★★
SiS Beta Fuel	40g	Milder	★★★★★
Maurten Gel 100	25g	Jelly-like	★★★★★
Powergel	27g	Average	★★★

Energy Bars

Brand	Carbs per bar	Protein	Best For
Clif Bar	42g	9g	Early bike leg
PowerBar Energize	27g	4g	Mid bike leg
Maurten Solid	44g	3g	Bike leg
Honey Stinger Waffle	21g	1g	Before the run

Drinks

Brand	Carbs per bottle	Sodium	Review
Gatorade Endurance	36g/591ml	300mg	Well balanced
SiS Go Electrolyte	36g/500ml	280mg	On the sweet side
Tailwind	25g/500ml	310mg	Easy to digest
Maurten Drink Mix 320	80g/500ml	100mg	High carb

8. Common Fueling Timing Mistakes

1. Eating too much before training: Starting before the stomach has emptied leads to bloating during exercise
2. Not fueling in the first hour: Waiting until you’re already tired means the stomach has already shut down
3. Taking too much at once: More than 60g of carbs per 30 minutes can’t be absorbed in time
4. Fueling without drinking: Gels need water to be absorbed
5. Trying new products on race day: Fueling products never tested in training

9. Gastric Response to Fueling

Gastric Emptying Rates

• Water: 15–20 minutes
• Sports drink: 30–40 minutes
• Gel (with water): 30–45 minutes
• Energy bar: 60–90 minutes
• Solid food: 90–120 minutes

Warning Signs of Stomach Distress

• Nausea, urge to vomit → Immediately switch to water only, stop taking in sugar
• Bloating → Slow down the fueling pace
• Reflux → Chew mint gum, take deep breaths
• Diarrhea → Too much caffeine or artificial sweeteners in fueling products

10. Real-World Example: 113-Distance Brick Simulation

2 Hours Before Training

• 2 slices of whole wheat bread + 2 eggs + 1 banana + black coffee
• Approximately 80g carbs + 25g protein

Bike Leg (3 hours)

• 0:30 SiS Gel
• 0:50 Half a banana
• 1:10 SiS Gel
• 1:30 Half a Clif Bar
• 1:50 SiS Gel
• 2:10 Half a banana
• 2:30 SiS Gel
• 2:50 1 salt tablet + gel
• Water: 200ml every 20 minutes (approximately 1800ml total)

Run Leg (45 minutes)

• 0:15 Half a gel + 100ml sports drink
• 0:35 1 salt tablet + water
• Water: 100ml every 10 minutes

Within 30 Minutes After Training

• 500ml chocolate milk + banana
• Approximately 80g carbs + 30g protein

There is no single right answer for fueling strategy—testing and finding the approach that works for you through Brick training is the core homework for preparing for a triathlon.

Related Reading

• Triathlon Three-Leg Fueling Tactics: Nutrition Strategies Before the Swim, on the Bike, and on the Run
• 70.3 Fueling Engineering: The Feeding Assembly Line for the 90km Bike Leg
• Cycling Race Fueling Strategy: What to Put in Your Pockets and When to Eat
• The Physiology of Brick Training: Why Your Legs Feel Like Lead After Getting Off the Bike