If you've ever tried running immediately after a hard bike ride, you know the sensation—legs that feel like concrete, a body that doesn't quite cooperate, and a pace that seems impossibly slow. This bike-to-run transition is one of triathlon's unique challenges, and mastering it through brick workouts is essential for race-day success. This comprehensive guide covers everything from the physiology of running off the bike to race-specific brick protocols for every triathlon distance.
What Are Brick Workouts?
A brick workout combines two disciplines performed back-to-back with minimal transition time, simulating race conditions. While "brick" most commonly refers to a bike-then-run session, the term can apply to any combination: swim-bike, run-bike, or even swim-run.
Origin of the Term "Brick"
Several theories exist for the name: the sensation of "brick-like" legs during the run, the combination of activities being "bricked" together like building blocks, or the founder of the workout being Matt Brick. Whatever the origin, the workout has become a triathlon training staple.
The Most Common Brick Format
The standard triathlon brick consists of:
- Bike Segment: 45 minutes to 3+ hours, depending on race distance
- Transition: 1-5 minutes (practice race-like speed)
- Run Segment: 10-60+ minutes, often starting at race pace
The key is keeping the transition quick—you're training your body to adapt to the stress of changing activities, and a long break defeats the purpose.
The Science Behind Running Off the Bike
Running immediately after cycling is uniquely challenging due to several physiological factors:
Muscle Recruitment Changes
Cycling and running use the same muscle groups differently:
- Hip Flexion Range: Cycling uses 75-110° of hip flexion; running uses 10-50°
- Muscle Length: Quadriceps are shortened on the bike but must lengthen for running stride
- Firing Patterns: Neural patterns optimized for cycling must rapidly switch to running coordination
- Calf Engagement: Limited eccentric calf loading on bike versus significant impact absorption during running
Blood Flow Redistribution
After cycling, blood has pooled in the lower extremities and working muscles. When you start running:
- Blood must redistribute to different muscle fiber patterns
- Venous return mechanisms change from seated to upright posture
- Heart rate temporarily spikes as the cardiovascular system adapts
- Perceived effort is significantly higher for the same absolute pace
Glycogen Depletion and Metabolic State
The Pre-Fatigue Effect
After cycling, muscles begin the run with depleted glycogen stores, accumulated metabolic byproducts, and potential dehydration. This "pre-fatigue" means running economy is compromised and fuel sources are limited—exactly the conditions you'll face in a race.
Benefits of Brick Training
Physiological Adaptations
- • Faster blood redistribution
- • Improved muscle recruitment switching
- • Better running economy post-bike
- • Enhanced metabolic flexibility
Neuromuscular Benefits
- • Quicker adaptation to running gait
- • Improved coordination under fatigue
- • Better running form maintenance
- • Reduced "jelly legs" sensation
Mental Preparation
- • Familiarity with race sensations
- • Confidence in pacing strategy
- • Reduced race-day anxiety
- • Mental toughness development
Practical Skills
- • Transition practice
- • Nutrition strategy testing
- • Equipment rehearsal
- • Pacing calibration
Types of Brick Workouts
1. Long Bike + Short Run
Focus: Practice running off tired legs after race-distance or near-race-distance cycling
Example: 3-hour bike + 20-30 min run at goal race pace
2. Short Bike + Long Run
Focus: Build running endurance with tired legs without excessive bike fatigue
Example: 45-60 min bike + 60-90 min run
3. Race-Pace Simulation
Focus: Practice exact race intensity and nutrition strategy
Example: Race-distance bike at race intensity + first miles of race-distance run at goal pace
4. Transition Repeats
Focus: Practice quick transitions and immediate running adaptation
Example: 4x (15 min bike + 5 min run) with full transition practice each time
5. Intensity Brick
Focus: High-intensity work on fatigued legs for neuromuscular adaptation
Example: 60 min bike with final 20 min at threshold + 4x800m intervals with recovery jog
Sprint Distance Brick Workouts
Sprint triathlons (750m swim, 20km bike, 5km run) demand speed and quick transitions. Bricks should emphasize intensity.
Key Sprint Brick Workouts
Workout 1: Race Simulation
20km bike at race effort → 5km run at race pace
Workout 2: Speed Focus
30 min bike with 3x3 min hard → 15 min run with 4x2 min at 5K pace
Workout 3: Transition Practice
4x (10 min hard bike + 5 min tempo run) with full transition each time
Olympic Distance Brick Workouts
Olympic distance (1.5km swim, 40km bike, 10km run) requires sustained threshold effort and run durability.
Key Olympic Brick Workouts
Workout 1: Full Simulation
40km bike at race effort → 10km run at goal race pace
Workout 2: Threshold Brick
60 min bike with 2x15 min at threshold → 30 min run with 2x10 min at half marathon pace
Workout 3: Endurance Focus
75 min steady bike → 45 min progressive run (easy to tempo)
Half Ironman (70.3) Brick Workouts
Half Ironman (1.9km swim, 90km bike, 21.1km run) demands pacing discipline and running endurance.
Key 70.3 Brick Workouts
Workout 1: Race Simulation
3-hour bike at race power → 45-60 min run at goal race pace
Workout 2: Long Brick
4-hour easy bike → 30 min easy run (focus on legs feeling good late)
Workout 3: Quality Brick
2.5 hours bike with final 45 min at race effort → 13 miles at half marathon race pace
Nutrition Practice
70.3 brick workouts are essential opportunities to practice race nutrition. You should be taking in 60-90g carbs/hour on the bike and testing your run nutrition strategy during these sessions.
Ironman Distance Brick Workouts
Ironman (3.8km swim, 180km bike, 42.2km run) is about surviving the bike to have a good run. Brick training focuses on pacing and nutrition.
Key Ironman Brick Workouts
Workout 1: Long Simulation
5-6 hour bike at race power → 45-90 min run at goal IM marathon pace
Workout 2: Marathon Prep
3-hour steady bike → 2-hour run (includes race-pace segments)
Workout 3: Back-to-Back Days
Day 1: 5-hour bike | Day 2: 2.5-hour run (simulates accumulated fatigue)
Ironman Brick Caution
Full Ironman-distance brick simulations (6+ hour bike + long run) create enormous training stress. Use them sparingly (2-3 per build cycle) and ensure adequate recovery. Most training adaptation comes from consistent moderate bricks, not occasional massive efforts.
Transition Skills to Practice
Brick workouts are the ideal time to practice your T2 transition skills:
Dismount and Running Start
Practice dismounting before the line, running in cycling shoes to your spot, and the sequence of actions in transition.
Shoe Changes
Whether you use elastic laces, slip-on shoes, or traditional lacing, practice until it's automatic. Consider practicing with wet hands (simulating sweat).
Mental Checklist
Develop and rehearse your T2 mental checklist: helmet off, sunglasses, shoes, race belt, nutrition, go. Same order every time.
Immediate Run Pacing
Practice finding race pace within the first 200-400 meters. It's easy to go out too fast when legs feel terrible but you're excited. Discipline starts here.
Common Brick Workout Mistakes
1. Doing Too Many Bricks
Bricks are demanding sessions that require recovery. Most athletes benefit from 1-2 bricks per week at most, with some weeks having none. More isn't better—quality over quantity.
2. Running Too Fast
The first mile off the bike always feels terrible. Many athletes make the mistake of pushing through at a pace they can't sustain, leading to a death march later. Practice starting conservative and building.
3. Neglecting Easy Bricks
Not every brick needs to be race-pace intensity. Easy bike + easy run bricks still provide valuable neuromuscular adaptation with lower recovery cost.
4. Skipping Transition Practice
If you just throw on running shoes and head out, you're missing half the value of brick training. Set up a mock transition and practice the race-day sequence.
5. Ignoring Nutrition
Brick workouts are essential for testing race nutrition. If you're not practicing your fueling strategy during bricks, race day will be a mystery.
Programming Bricks Into Your Training
Weekly Frequency by Phase
| Phase | Bricks/Week | Focus |
|---|---|---|
| Base | 0-1 | Easy/moderate effort, get used to sensation |
| Build | 1-2 | Progressive intensity, longer durations |
| Peak | 1-2 | Race simulations, race-pace work |
| Taper | 0-1 | Short, sharp openers only |
Weekly Placement
- Weekend Long Brick: Most athletes do their longest brick on Saturday or Sunday, followed by a recovery day
- Midweek Short Brick: If doing two bricks, a shorter transition-focused brick midweek works well
- Day Before Rest Day: Always schedule bricks before rest or easy days, not before key interval sessions
Sample Training Weeks
Olympic Distance: Build Phase Week
Monday: Swim (focus) + easy run (30 min)
Tuesday: Bike intervals (60 min with 4x5 min at threshold)
Wednesday: Short brick: 45 min bike + 20 min run at race pace
Thursday: Swim + run intervals (6x800m at 10K pace)
Friday: Rest or easy swim
Saturday: Long brick: 75 min bike at race effort + 40 min run progressive to race pace
Sunday: Long easy run (60-75 min) OR recovery spin + swim
Half Ironman: Peak Phase Week
Monday: Swim (open water if possible) + easy run (40 min)
Tuesday: Bike threshold work (2.5 hours with 2x20 min at race power)
Wednesday: Short brick: 60 min steady bike + 25 min run with strides
Thursday: Swim + run tempo (45 min with 20 min at HM race pace)
Friday: Easy swim (30 min technique focus)
Saturday: Race simulation brick: 3-hour bike at race power + 50 min run at goal IM70.3 pace
Sunday: Recovery: Easy spin + stretching/yoga
Conclusion: Build Your Brick Foundation
Brick workouts are the bridge between training as a swimmer-cyclist-runner and racing as a triathlete. The sensations of running off the bike—the heavy legs, the awkward gait, the elevated heart rate—are uniquely triathlon challenges that can only be mastered through deliberate practice.
Start conservatively with your brick training, focusing first on the experience of running immediately after cycling. As you become comfortable, increase duration and intensity progressively. By race day, you'll have confidence in your ability to execute a strong run regardless of how the bike leg went.
Remember: the goal isn't to suffer through as many bricks as possible, but to arrive at the start line knowing exactly what to expect from your body during the crucial transition from bike to run.
Plan Your Training
Use our pace and zone calculators to set appropriate targets for your brick workouts.
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