Brick Workouts: Why and How to Train the Bike to Run

What is a brick workout?

A brick workout is a triathlon training session where you stack two disciplines back to back, almost always a bike ride followed immediately by a run, with little or no rest in between. The whole point is to teach your body and brain to handle the jarring switch from pedalling to running that hits you on race day. If you have ever climbed off the bike and felt like your legs belonged to someone else, you already understand why brick workouts exist.

Here is the thing most beginners miss: triathlon is not three separate sports glued together. It is one continuous event, and the seams between disciplines are where races are won and lost. You can be a strong cyclist and a decent runner on fresh legs, and still fall apart in the first kilometre off the bike because you never trained that exact moment. The brick is the only session that rehearses it. At TrainingZones.io we treat the brick as the most sport-specific session in a triathlete's week, the one that turns three fitnesses into one race.

Most triathletes do their bricks as bike-to-run, because that transition (T2) is by far the hardest. Some coaches also use swim-to-bike bricks, especially before a first open water race, but when people say "brick" without qualifying it, they almost always mean ride then run.

Why is it called a brick workout?

The name "brick" comes from the idea of stacking two workouts on top of each other like bricks in a wall. That is the explanation most coaches give, and it is the simplest one. You take a bike session and a run session and lay them directly on top of one another, no gap, no recovery.

There is a second, more folkloric story that triathletes love to repeat: that "brick" stands for Bike-Run-ICK, or that it describes how your legs feel like solid bricks when you start running. Whether or not that origin is real, it captures the sensation perfectly. The first few minutes of a brick run feel heavy, clumsy, and slightly panicky, like your legs forgot how to run. That feeling is the whole reason the session matters, and the reason it has such a memorable name.

Why brick workouts matter (the jelly-legs problem)

Brick workouts matter because cycling and running share muscles but use them in completely different ways, and your body needs practice switching between the two under fatigue. On the bike, your legs work in a fixed, repetitive motion through a narrow range, with the saddle supporting your bodyweight. The moment you stand up and run, those same muscles have to absorb impact, produce elastic force, and control your whole bodyweight through a much wider range of motion. Your nervous system has to reorganise itself in seconds.

That reorganisation is what creates the famous "jelly legs" or "brick legs" feeling. Blood is pooled in your cycling muscles, your stride is short and shuffly, your heart rate is high, and your running form is a mess for the first few minutes. Research on the bike-to-run transition shows that run economy and mechanics are most disrupted in roughly the first 5 to 10 minutes off the bike, then gradually normalise. Train that window often enough and your body learns to shorten it.

The benefits stack up over a season:

• Faster, smoother transitions. Your nervous system learns to anticipate the change, so blood flow redistributes faster and your stride opens up sooner.
• Better run-off-the-bike economy. You waste less energy fighting your own legs in those critical first minutes.
• Time-efficient overload. A 15-minute run off the bike stresses your body more than a fresh 15-minute easy run, because you are already fatigued. You get more adaptation per minute.
• Psychological confidence. Every time your legs come around in training, you bank proof that they will come around on race day too. On race day that belief is worth a lot.

Key takeaway: the brick does not just build fitness, it builds a specific skill. The skill of running well when your legs do not want to.

How to do a brick workout

To do a brick workout, finish your bike session, transition into your running gear as fast as you reasonably can, and head straight out on the run with no real rest. The faster and more race-like your transition, the more the session carries over. Here is a simple structure that works for most triathletes:

1. Warm up on the bike for 10 to 15 minutes of easy spinning before any harder efforts.
2. Ride the main set at the intensity your phase calls for (steady aerobic in base, race-pace efforts as you get closer to your event).
3. Set your run gear out in advance so the change takes under a minute, shoes loosened, race belt and cap ready.
4. Transition fast, rack or lean the bike, swap shoes, and start running immediately. Do not sit down.
5. Run the first few minutes deliberately controlled, with a slightly quicker, shorter stride, and let your form settle before you chase pace.
6. Build into your target pace once the heaviness fades, usually after 5 to 10 minutes.

Do not panic when the run feels awful at the start, that is the session working, not a sign of poor fitness. Keep early bricks short and add length gradually. Use the run-off-the-bike to dial in your target pace with our pace calculator, and plan how your brick fits the wider race build with our triathlon calculator.

Sample brick sessions by race distance

A good brick scales with your race: a sprint athlete needs a short, sharp brick, while an Ironman athlete needs long rides finished with a moderate run. The builder below gives you a starting point for bike and run duration, how often to do it, and what to focus on for each phase of your training.

A few notes on reading those numbers. The run off the bike does not need to be long to be effective, especially early on. For a sprint or Olympic athlete, even 10 to 15 minutes teaches the transition. For 70.3 and Ironman, the value shifts toward long rides finished with a steady run that rehearses race-day fatigue and fuelling. In every case, the bike does most of the work and the run is the specific stimulus on top.

As your race approaches, the brick should look more and more like your event: race-pace effort on the bike, goal pace on the run, the exact nutrition you will use, and a transition you have practised. As we always say at TrainingZones.io, your peak-phase brick is a dress rehearsal, not a fitness test.

How often should you do brick workouts?

Most triathletes should do one brick workout per week, building to one or two in the final weeks before a key race. Bricks are demanding and specific, so more is not better, especially in your base phase when general fitness matters more than race specificity.

Early in the season, a brick every couple of weeks is plenty. As you move into the build phase, a weekly brick becomes the anchor of your training week, usually on the weekend when you have time for the longer ride. In the final three to four weeks before your race, a slightly shorter but very race-specific brick once or twice a week sharpens everything without digging a fatigue hole. During taper, keep one short, snappy brick to stay sharp, then back right off.

The classic mistake is treating every weekend ride as a brick and bolting a run onto all of them. That just leaves you constantly tired and your run quality suffers. One quality brick, done with intent, beats three half-hearted ones.

What to eat before and during a brick workout

Fuel a brick workout like a mini race: eat a carbohydrate-rich meal two to three hours before, and take on carbohydrate during the bike so you start the run already topped up. The run off the bike is where under-fuelling shows up first, because your stomach is jostled and your energy is already dipping.

For shorter bricks under about 75 minutes, water and maybe a single gel are enough. For longer 70.3 and Ironman bricks, treat the bike as your feeding window: aim for the carbohydrate intake you plan to use on race day, often in the range of 60 to 90 grams per hour for trained athletes, and practise drinking on the move. The long brick is the best place to find out that your race nutrition plan actually sits well when you start running, long before it matters. Dial in your fuelling numbers with our race nutrition tools, and never test something new on race day.

Common brick workout mistakes

The most common brick mistake is going too hard on the bike, so the run becomes a survival shuffle that teaches bad habits instead of good ones. A brick is about quality running off the bike, not destroying yourself on the bike and then jogging home broken.

Watch out for these traps:

• Sandbagging the run. Treating the run as a token 5-minute jog. Make it long enough to get through the heavy-legs phase and into real running.
• A slow, lazy transition. Sitting down, changing socks, scrolling your phone. The transition should be quick and race-like, or you lose the specific stimulus.
• Only ever doing easy bricks. As you near your race, you need bricks at race intensity, not just easy aerobic ones.
• Starting the run too fast. Overstriding in the first minute on heavy legs is how you tighten up or get injured. Control the start.
• Ignoring nutrition. Long bricks are your nutrition lab. Skipping fuelling practice is a wasted opportunity.

Get those right and the brick becomes the session that makes everything else in your triathlon training add up.

Frequently Asked Questions About Brick Workouts

What is a brick workout?

A brick workout is a triathlon session where you do two disciplines back to back, almost always a bike ride followed immediately by a run, with minimal rest. It trains your body to handle the bike-to-run transition that you face on race day.

Why is it called a brick workout?

The most common explanation is that you stack two workouts on top of each other like bricks. Triathletes also joke that it stands for Bike-Run-ICK, or that it describes how your legs feel like solid bricks when you start running off the bike.

How often should I do brick workouts?

Most triathletes do one brick per week, building to one or two in the weeks before a key race. In the base phase, once every two weeks is enough. Avoid turning every ride into a brick, as that just leaves you tired.

How long should a brick workout be?

It depends on your race. A sprint brick might be a 40-minute bike with a 10 to 15 minute run, while an Ironman brick can be a long ride finished with a 45 to 60 minute run. The run off the bike does not need to be long to be effective.

What should I eat before a brick workout?

Eat a carbohydrate-rich meal two to three hours beforehand, and take on carbohydrate during the bike so you start the run topped up. For long bricks, practise your exact race nutrition, around 60 to 90 grams of carbohydrate per hour for trained athletes.

Do brick workouts make you a faster runner?

Brick workouts make you a faster runner specifically off the bike, which is what matters in triathlon. They improve your run economy and form in the critical first minutes of the run, and build the confidence that your legs will come around.

References

• Bonacci, J., et al. (2010). Neuromuscular adaptations to training, injury and passive interventions. Sports Medicine, 40(3):203-213.
• Millet, G. P., & Vleck, V. E. (2000). Physiological and biomechanical adaptations to the cycle-to-run transition in Olympic triathlon. British Journal of Sports Medicine, 34(5):384-390.
• USA Triathlon (2023). How to Use Brick Workouts in Triathlon Training.