Brick training is two disciplines performed back-to-back. For most triathletes, that means cycling, making a short and safe transition, then running. The name describes the session structure; it does not prove a particular physiological mechanism or prescribe how long either part must be.
This page owns Roadman’s broad brick training and brick workout answer. The brick-workout glossary entry is the short definition. The bike-to-run guide for cyclists and duathletes covers riders who are new to running. This guide explains the evidence, the programming choices and the long-course boundary.
The short answer: what a brick workout is for
A useful brick has one primary job:
- Transition familiarity: learn how easy running feels immediately after cycling and practise a calm kit change.
- Race execution: rehearse bike pacing, the first run kilometres, equipment, course cues and the complete fuelling plan.
- Schedule efficiency: combine two sessions deliberately when the athlete understands the extra fatigue and impact.
“Build fitness” is too broad. The bike and run can build fitness separately. A brick earns its place when their sequence matters.
What happens when you run after cycling?
The strongest current summary is a 2022 systematic review of 39 studies. Most included studies found a detrimental performance effect when running followed cycling, and perceived effort tended to rise. The same review found conflicting biomechanical and physiological results because cycling protocols, comparison runs, athlete levels and outcome measures differed.
That is the honest version of “jelly legs”. Some athletes change stride length, muscle activity, posture or running economy; some group averages change little; experienced triathletes may show smaller disturbances. The evidence does not justify telling every rider that blood is “pooled” in the wrong muscles, the brain is trapped in a pedalling pattern or the first run will be exactly 10–15% slower.
The earlier Millet and Vleck review reported that the energy cost of running after cycling varied with ability level and conditions. A 2019 crossover study in ten trained, non-elite triathletes found a shorter distance and 0.1 m lower stride length in a maximal 12-minute run after cycling than in an isolated run, with no reported difference in several other measured variables. That is useful evidence for a transition effect under one protocol—not a universal pace-loss formula.
What the evidence does not establish
One ideal weekly frequency
Acute cycle-to-run studies can show what changed in a test. They do not establish that every triathlete should do one, two or three bricks per week across a season.
Frequency depends on:
- whether the athlete has a real transition or execution problem;
- current running durability and impact tolerance;
- race distance and weeks remaining;
- the bike and run load already in the week;
- injury history and current symptoms; and
- the recovery cost of the proposed session.
The least brick work that solves the job is a better starting point than an internet quota.
One cadence trick before the run
Cadence advice is a good example of a plausible rule outrunning the evidence. In eight well-trained triathletes, cycling before a 10 km treadmill run slowed the run compared with an isolated effort, but low, preferred and high cadences did not change overall 10 km time. In a different eight-athlete laboratory study, finishing the bike 20% below freely chosen cadence increased subsequent running time to fatigue compared with freely chosen or higher cadence.
Different tasks produced different answers. Do not force an unfamiliar spin or grind because it appeared in a generic plan. Practise a sustainable race-relevant cadence and compare your own run response.
One mandatory monster brick
Roadman previously called a four-to-five-hour bike plus a 60-to-90-minute run “the single most predictive session” in an Ironman programme. We found no comparative evidence supporting that claim.
A long brick can rehearse pacing, kit, carrying and fuelling. It also creates a large training and recovery cost. Many of those jobs can be tested with a representative bike followed by a shorter run, while long-run durability is developed in a standalone session. A coach may still choose a longer rehearsal for a prepared athlete; that is an individual programming decision, not a validated requirement.
Five brick workouts, each with one job
These are templates, not prescriptions. Durations and intensities must fit the athlete’s recent training, event and recovery.
| Brick | Bike | Transition run | Primary job |
|---|---|---|---|
| First transition | 45–60 min easy | 8–12 min easy or run-walk | Learn the sensation and kit sequence |
| Aerobic maintenance | 75–120 min easy | 10–20 min easy | Repeat a calm transition without adding a second hard session |
| Bike-quality brick | Planned bike intervals inside 60–90 min | 10–15 min easy | Learn to control the first run after a demanding bike |
| Race-execution brick | Race-relevant bike duration and effort | 15–30 min at controlled planned effort | Test pacing, shoes, course cues and early-run restraint |
| Long-course rehearsal | Individually scaled long ride | Short enough to preserve the wider run plan | Test carrying, fuelling, comfort and the opening run plan |
1. First transition brick
Ride easily for 45–60 minutes. Transition without rushing, then run or run-walk for 8–12 easy minutes. The goal is observation: how quickly effort settles, whether equipment works and whether any pain or gait change appears.
Athletes without recent running should build standalone run tolerance first. Cardiovascular fitness from cycling does not automatically prepare bone, tendon and muscle for an abrupt increase in impact load.
2. Aerobic maintenance brick
Add a 10–20-minute easy run after a familiar aerobic ride. Keep both components controlled. This works when the athlete needs repeated transition familiarity but the week cannot absorb another hard run.
3. Bike-quality, easy-run brick
Complete the day’s planned bike intervals, then run easily for 10–15 minutes. The run is not a second threshold test. It teaches the athlete to stop chasing speed when effort perception is altered after a hard bike.
4. Race-execution brick
Use the bike intensity you actually plan to hold, make the real transition and run the opening 15–30 minutes at planned effort. Record power or effort on the bike, transition time, early-run pace and RPE. The question is whether the plan remains controlled—not whether the athlete can win training.
5. Long-course rehearsal
Choose only the duration required to expose the practical problem: aero comfort, bottle access, clothing, pacing drift, stomach tolerance or the first run kilometres. Do not copy a five-hour-plus-ninety-minute formula without considering recent long rides, long runs and recovery.
For race-specific bike work, use the Ironman bike training-plan guide. For target power, use the Ironman pacing guide. Those are separate decisions from the brick’s run duration.
How to progress brick training
Progress one variable at a time:
- establish an easy transition without pain or uncontrolled effort;
- repeat it until equipment and pacing are calm;
- extend the ride or make it more race-specific;
- only then extend or intensify the run when that serves the event; and
- protect the next key standalone run and bike session.
Do not increase bike duration, bike intensity, run duration and run pace together. If the next two days are materially worse, the brick may have exceeded its job even when the session itself looked impressive.
Pacing the bike and the first run
The simplest brick metric is execution drift.
On the bike, compare planned with completed power, heart rate or RPE. On the run, compare the first ten minutes with the settled portion. A large early pace surge, rising effort at the same pace or inability to hold the planned run can point to bike pacing, heat, fuelling, durability or an unrealistic run target. It does not diagnose which one by itself.
Start the run at planned effort, not at the pace that fresh legs could hold. Let the measured response decide whether the target survives contact with the bike.
Fuelling a brick workout
Roadman’s previous page prescribed 90 g of carbohydrate per hour as though it applied to every race-specific brick. It does not.
Published guidance commonly uses 30–60 g/h for longer exercise and up to 90 g/h for events beyond roughly 2.5 hours when multiple transportable carbohydrates are useful and the dose has been practised (Burke et al.; Jeukendrup). A 2023 meta-analysis supports carbohydrate during endurance exercise overall while showing that duration, protocol and training status affect the result.
For a race-fuelling brick:
- set the hourly carbohydrate target from duration and demand;
- count drink, gels, chews and food in one total;
- plan fluid separately for conditions and access;
- count total caffeine, not caffeinated packets;
- continue only what the athlete expects to tolerate on the run; and
- change one variable between rehearsals.
Use the in-ride cycling-nutrition guide and fuelling calculator to build the complete plan. Gut practice can help some athletes, but the systematic review of gut-training studies does not establish a guaranteed adaptation schedule.
When not to do a brick
Skip or reduce the brick when:
- the athlete cannot yet complete the proposed run comfortably on fresh legs;
- there is new or worsening pain, altered gait, illness or unresolved injury;
- the session would compromise the week’s priority standalone run;
- heat, route or traffic makes the transition unsafe;
- the only goal is proving toughness; or
- recovery from the previous block is incomplete.
Persistent pain, swelling, inability to bear weight, chest pain, fainting, severe breathlessness or neurological symptoms require appropriate medical assessment. A brick is not a diagnostic test.
Roadman’s brick-training verdict
Practise the sequence because triathlon requires the sequence. Keep the claim proportional to the evidence: cycling often makes the following run harder, but individual response and mechanisms vary, and research does not establish one perfect cadence, weekly frequency or long-course simulation.
Give every brick one job. Start with a short easy transition, progress one variable, rehearse race execution when the foundation exists and count the run as real training load. The best brick is the smallest session that answers the race question without damaging the rest of the plan.
This guide was last checked on 26 August 2026. For a cyclist-first introduction, use brick workouts for cyclists and duathletes. For an individual training route, see triathlon cycling coaching. Corrections can be submitted through the Roadman corrections page.