Every triathlete has felt it. You step off the bike after a long effort, lace up the run shoes, and the first 5 minutes of the run feel like running through wet concrete on someone else's legs. Your cadence is wrong, your breathing is wrong, your stride is short, and the watch pace is somehow slower than you ran last week on fresh legs. Then, usually around the 10 to 15 minute mark, something clicks back into place — the legs remember what they're supposed to do, the pace drops, and the run starts to feel like running again. Those first minutes are what brick workouts exist to train.
This guide is the practical, evidence-based version of brick workouts. It will tell you exactly what physiology the bike-to-run transition actually involves, how often to schedule bricks in each phase of a triathlon training cycle, what session templates work for sprint, Olympic, 70.3, and full Ironman, why long brick runs are usually a mistake, and how to build race-rehearsal bricks that actually teach the body what race day will feel like. The word 'brick' has a dozen claimed origins — the most common are Bike-Run-I-C-K, or a tribute to the late triathlon coach Matt Brick, or just the sensation of the legs afterward. Whatever the origin, the session is central to triathlon training, and most amateurs execute it wrong.
What does the bike-to-run transition actually do to the body?
The bike-to-run transition is not just a change of equipment. It's a change of motor pattern, a change of muscle recruitment, a change of cardiovascular demand, and a change of vascular distribution — all happening in the span of a few hundred meters. Understanding what the body is doing explains why the transition feels so strange and why training for it matters.
On the bike, the dominant muscles are the quadriceps, the gluteus maximus, and (at higher efforts) the calves. Hip extension and knee extension drive the pedal stroke. The ankle stays relatively neutral, the foot doesn't leave the pedal, and the impact forces are essentially zero. When you step off the bike and begin running, the muscle recruitment flips: the plantar flexors (calves, Achilles tendon) become primary because every stride involves pushing off the ground, the hamstrings become active in the stance phase of running in a way they aren't during cycling, and the foot strike has to absorb 2 to 3 times body weight with each step. None of those patterns have been primed by the previous 2 to 6 hours of cycling.
At the same time, blood flow has to redistribute. During cycling, a disproportionate amount of blood is shunted to the cycling-dominant muscles (quads, glutes, cycling posture stabilizers). When running starts, blood has to redistribute to the calves, plantar flexors, and upper body stabilizers needed for running gait. This redistribution takes minutes, and during those minutes the run feels strangely inefficient — the legs are getting less blood than the demands require, and the overall cardiovascular system is working harder to deliver it.
The nervous system has its own transition problem. Running gait is a learned motor program, and switching from the cycling motor program to the running motor program while fatigued produces the characteristic 'jelly leg' feeling of the first 5 to 15 minutes of a brick. What's actually happening is that the central nervous system is reprogramming motor recruitment patterns in real time, and the initial output is sloppy and inefficient. This reprogramming speeds up with training — athletes who do regular bricks transition faster and feel less disoriented in those first minutes than athletes who don't.
What is the point of a brick workout if the adaptation happens in 15 minutes?
The critical physiological adaptation of brick training — the neuromuscular reprogramming, the vascular redistribution, the learned motor shift — happens in the first 15 to 20 minutes of the run off the bike. This is the window where the body is doing the thing the session is designed to train. After that window, you are essentially just running on tired legs, which is a different (and arguably less specific) training stimulus.
This has a surprising practical implication that many triathletes miss: most brick runs do not need to be long. A 20-minute brick run trains the transition. A 60-minute brick run trains the transition for 15 minutes and then does 45 minutes of generic fatigued running that could have been a regular long run the next day with less total fatigue cost. The 45 extra minutes add cost without adding adaptation for most athletes.
The exception is race rehearsal bricks in the specific phase of an Ironman or 70.3 build. These long bricks exist to rehearse the race experience — the duration, the fueling, the mental demands, the cumulative fatigue — not to train the transition physiology. They're valuable in the final 6 to 8 weeks of Ironman preparation, but they should be rare (1 to 2 per cycle), carefully positioned, and understood as a different session type than a normal training brick.
The rule of thumb is: a brick trains the transition; a race rehearsal trains the race. Most of the brick work in a plan should be the former. Long bricks every week are a classic amateur over-training pattern that produces fatigue without adding specific adaptation.
How often should you schedule brick workouts? (By training phase)
Brick frequency scales with training phase and race distance. The general pattern is to introduce bricks during base phase, increase frequency during build, and include at least one race-rehearsal brick in the specific phase before the race. The table below is the practical reference.
| Phase | Frequency | Structure | Purpose |
|---|---|---|---|
| Base | 1/week | Weekend ride + 15–20 min easy Z2 run | Keep the transition pattern alive |
| Early build | 1–2/week | Weekend + midweek brick, with race-pace segments in the run | Introduce race intensity off the bike |
| Late build / specific | 1–2/week | One progressing toward race-rehearsal length | Rehearse the race experience |
| Taper | 1 short/week | 60 min ride + 10–15 min easy run | Pattern fresh without fatigue |
| Race week | 0–1 very short | 30 min spin + 10 min easy run 3–5 days before | Transition rehearsal, no intensity |
Sprint and Olympic triathletes use fewer bricks than long-course athletes. Long-course athletes (Ironman, 70.3) need more because the bike is long enough to substantially alter the neuromuscular state before the run begins.
What does a good brick workout actually look like?
The structure depends on race distance and training phase, but a few session templates are standard in coaching practice.
- Base-phase easy brick (90 min total): 60 to 75 minutes of Zone 2 riding, T2 transition under 5 minutes (rack bike, change shoes, hat, drink), 15 to 20 minutes of Zone 2 running. No intensity, no stress, just pattern-building. Ideal for a weekend morning during base.
- Build-phase race-pace brick (90 to 120 min total): 60 to 90 minutes of riding including 2 to 3 race-pace intervals of 5 to 10 minutes, T2 transition under 3 minutes, 20 to 30 minutes of running with the first 10 minutes at race pace and the rest easy. This is the session that teaches the legs and lungs what race pace feels like off the bike.
- 70.3 race-rehearsal brick (2h15 to 2h45 total): 90 minutes riding at 70.3 race IF (0.78 to 0.85), realistic transition with race-day shoes and kit, 30 to 40 minutes running at goal race pace. This is the key rehearsal session in the 4 to 6 weeks before a 70.3. Do 2 of them in the build.
- Ironman race-rehearsal brick (5h to 6h30 total): 4 to 5 hours riding at Ironman IF (0.65 to 0.72), full race-day fueling rehearsed, realistic T2, then 45 to 75 minutes running at Ironman goal pace (which is usually 30 to 60 seconds per km slower than open marathon pace). Peaks 4 to 8 weeks before the race. Usually done once or twice in the final build.
- Reverse brick (less common, 60 to 90 min total): a short run followed by a short ride. Useful for nervous-system coordination and for swimmers transitioning from a swim-to-bike race morning, but not a substitute for bike-to-run bricks. Most plans do not need reverse bricks.
A well-executed brick spends more time on the planning than the execution. The transition has to be rehearsed: bike racked where you can find it, run shoes unlaced and ready to go, hat and race belt laid out, nutrition accessible. The first time you practice T2 in training should not be race morning. Most time lost in real-race transitions is to decisions that could have been pre-made in a training brick.
How does fueling interact with brick workouts?
Fueling on a brick should match the fueling planned for the race. The point of the brick is not just to train the body — it's to rehearse the entire package of bike pace, fueling rate, hydration, and run execution in the order they'll happen on race day. A brick done without the race-day fueling plan is missing half the value.
For a 70.3 race-rehearsal brick, the athlete should take in 75 to 100 grams of carbs per hour on the bike portion and practice taking a gel plus water in the first 10 minutes of the run. For an Ironman race-rehearsal brick, the athlete should hit race-day fueling on the bike (80 to 100 g/h) and rehearse the early-marathon nutrition pattern they plan to use — typically 60 to 90 grams per hour on the run, with specific attention to how the gut responds in the first 20 minutes after T2, when many Ironman athletes experience GI distress.
The second point of brick fueling is discovering gut tolerance limits in a controlled environment. If 100 g/h on the bike followed by a gel in the first mile of the run produces cramping or nausea in training, that's the best possible time to find out — while you can still adjust the plan. Race day is a bad time to discover that your pre-planned fueling rate doesn't survive the transition.
What are the most common brick workout mistakes?
Five mistakes catch most amateur triathletes during brick training.
- Making every brick run too long. The neuromuscular adaptation of a brick happens in the first 15 to 20 minutes. Running 60 minutes off every long ride adds fatigue without adding specific adaptation and is a fast route to overtraining. Short bricks, often, beat long bricks, rarely.
- Skipping the transition rehearsal. Stepping off the bike, walking to the shoes, casually changing over, and taking 8 minutes to start the run defeats the purpose of the session. The transition should be rehearsed as if it were race day — quick, pre-organized, and under time pressure. If T2 in training is more than 2 to 3 minutes, something is wrong.
- Riding the bike portion too easy. A brick is only specific if the bike leg is ridden at something close to the intensity you'll use in the race. A 2-hour Zone 2 bike followed by a run trains the general transition pattern, but it doesn't replicate the neuromuscular state of a race-paced 70.3 or Ironman bike. At least some bricks should include race-intensity bike work.
- Not practicing race-day nutrition. Brick workouts are rehearsal sessions. Fueling during the brick is part of the rehearsal, and athletes who 'don't bother' with gels on training bricks are training a different session than they'll race.
- Running the brick run as hard as possible. The point of the brick is specific adaptation and rehearsal, not a second race. Most brick runs should be at race pace or slower, not at all-out effort. Hammering the brick run reliably produces overtraining without making the race go better.
How do you measure whether brick training is working?
The clearest sign that bricks are working is that the first 10 to 15 minutes off the bike stop feeling strange. Experienced triathletes with good brick training transition into run pace within 2 to 5 minutes; untrained athletes take 10 to 20 minutes and sometimes never fully find their run cadence during a race. If your brick runs still feel like running through concrete at mile 3 of a 70.3, you're not doing enough bricks or you're not doing them at race intensity.
A secondary measure is the delta between open-run pace and run-off-the-bike pace. A well-trained triathlete can run off the bike within 10 to 20 seconds per km of their open-run pace at the same effort. An under-trained triathlete is 30 to 60 seconds per km slower. Tracking this over time is one of the better indicators that brick training is delivering.
A third, subtler measure is stride rate and cadence at the start of the brick run. Athletes who train the transition consistently have normal-looking cadence within a minute or two of starting the run. Athletes who don't have noticeably shorter, shufflier strides for 5 to 10 minutes. This is visible in running watch cadence data or on video if you care to check.
Key takeaways
- A brick workout is a training session where a run immediately follows a bike ride, designed to train the bike-to-run transition physiology.
- The transition involves distinct muscle recruitment changes, vascular redistribution, and motor-pattern reprogramming that happen in the first 15 to 20 minutes of the run.
- Most brick runs do not need to be long. 15 to 20 minutes is enough for the transition adaptation; longer runs off the bike mostly add fatigue without adding specific benefit.
- Brick frequency is 1 per week in base, 1 to 2 per week in build, and includes 1 to 2 longer race-rehearsal bricks in the specific phase before an Ironman or 70.3.
- Race-rehearsal bricks are a different session type than normal bricks and should include full race-day fueling, realistic transition, and race pace.
- The transition itself (T2) should be rehearsed under time pressure in training, not experienced for the first time on race day.
- Fueling during brick workouts is part of the rehearsal and should match the race-day plan, including the first 10 minutes of the brick run where most in-race GI distress shows up.
- Progress shows up as faster transitions (legs find running cadence within 2 to 5 minutes instead of 10 to 15) and smaller gap between open-run pace and brick-run pace.
Frequently asked questions
How long should a brick run actually be?
For most training bricks, 15 to 20 minutes is enough. The neuromuscular adaptation of running off the bike happens in that first window, and additional running beyond it mostly adds fatigue without adding transition-specific adaptation. Race-rehearsal bricks in the specific phase of an Ironman build can be longer (45 to 75 minutes) because their purpose is different — they're rehearsing the race, not just training the transition. Every other brick run should usually be short.
How often should I do brick workouts?
1 per week in base phase, 1 to 2 per week in build phase, and 1 to 2 race-rehearsal bricks in the specific phase before an Ironman or 70.3. More than 2 bricks per week is almost always too many for amateur triathletes — the recovery cost of run-off-bike sessions is high, and the marginal benefit of adding more drops quickly. Shorter, more frequent bricks beat longer, more exhausting ones.
Should I run faster or slower than my open-run pace on a brick?
Most of the time, match your open-run pace at the same effort — which will feel slower for the first 5 to 10 minutes until the legs catch up. Build-phase bricks often include a 5 to 10 minute segment at race pace in the middle of the run. Race-rehearsal bricks are run at goal race pace, which for Ironman is typically 30 to 60 seconds per km slower than a standalone marathon would be. Very few brick runs should be all-out efforts.
Is a 10-minute run off a weekend ride enough to count as a brick?
Essentially yes, for base-phase pattern maintenance. A 10-minute run off a long ride keeps the transition alive, trains the legs to accept running after cycling, and adds minimal fatigue. It's not a race rehearsal, but it's a functional brick. Many coaches use short run-offs like this throughout the season to maintain the neuromuscular pattern without the recovery cost of longer brick runs.
Do I need to do bricks for a sprint or Olympic triathlon?
Yes, but less frequently than for 70.3 or Ironman. Sprint and Olympic races still have a bike-to-run transition, and the transition still costs time if you don't train it. But the shorter races are less neuromuscularly demanding, and one brick per week in build phase is usually enough. The specific-distance athlete who does a couple of race-rehearsal bricks before their key race is in a good position — the physiology is easier to train when the race is shorter.
What about swim-to-bike transitions? Should I train those?
Less commonly, and mostly in the final weeks before a race. Swim-to-bike (T1) is less neuromuscularly disruptive than bike-to-run — the transition from horizontal swimming to the bike is more about getting your heart rate under control and managing the early-bike chaos than about retraining muscle patterns. Most triathletes do not need formal T1 training sessions in a block. Some specific-phase swim-bike bricks in the final 4 to 6 weeks before a race are useful for rehearsing the full race start sequence, but they're not a frequent session type.
How CoreRise schedules brick workouts across your triathlon season
When you build a triathlon plan in CoreRise, brick workouts are scheduled deliberately across the phases of the season — not as a single template, but as progressively harder sessions that match where you are in the training cycle and where your next race is. Base-phase bricks are short and easy. Build-phase bricks introduce race-pace segments. Specific-phase bricks include full race-rehearsal sessions with the exact fueling protocol you'll use on race day, timed to the course profile and conditions. The coach spaces them so that recovery is protected and the quality of each brick session is high.
Cora will also walk you through how to structure the transition itself in training — the T2 rehearsal, the equipment layout, the fueling handoff from bike to run, the mental reset you'll need on race day. Most amateurs who lose 5 to 10 minutes to clumsy transitions in their first race have never actually practiced T2 under time pressure. The coach makes that rehearsal explicit and repeatable, so race morning is familiar instead of improvised.
- Brick workouts are phased across base, build, and specific, with length and intensity matched to your race distance and training phase.
- Race-rehearsal bricks are scheduled in the final 4 to 8 weeks before an Ironman or 70.3 with full fueling and transition practice.
- Most brick runs in the plan are short (15 to 25 minutes) because the neuromuscular adaptation happens early and longer runs add fatigue without extra benefit.
- T2 transition practice is built into the plan explicitly, not assumed — including equipment layout and timing targets.
- Brick fueling matches your race-day nutrition plan, so the gut gets rehearsed for the exact intake pattern race day will require.
Antoine Boudet is the founder of CoreRise. He finished Ironman 70.3 Oceanside in 2026 and writes the evidence-based Learn hub articles for runners, cyclists and triathletes, drawing on the research literature and his own training.