The Ironman marathon is not a marathon. It is a run off 180km of cycling, 2.4 miles of swimming, and four to seven hours of accumulated fatigue. Training for it as if it were a standalone run is the single most common error I see in age-group programmes.
Brick workouts are the tool that bridges that gap. Done well, they rehearse the exact neuromuscular and metabolic transition that decides your race. Done badly — which is how most athletes do them — they leave you chronically fatigued and slower on race day.
This article lays out ten specific sessions, organised by training phase, with duration, intensity, and placement in the week. No generic "ride then run" advice.
What brick workouts actually train
A brick workout is two disciplines completed back-to-back with minimal rest. In Ironman context, that almost always means bike-to-run. The name comes from how your legs feel in the first kilometre off the bike.
Three specific adaptations are trained. First, the neuromuscular switch: cycling recruits the quads heavily in a closed chain, while running loads the posterior chain and requires cadence 80–90+ steps per minute per leg. The first five minutes off the bike is where that transition happens, and it's trainable.
Second, substrate utilisation. After three to five hours of cycling, muscle glycogen is depleted and fat oxidation is elevated. Running in that state teaches the body to hold pace on mixed fuel, which is exactly the Ironman marathon scenario. Prof. Stephen Seiler's work on endurance adaptation reinforces that specificity matters most as you approach race day.
Third, pacing discipline under fatigue. Running at target Ironman pace feels easy at kilometre one and brutal at kilometre 32. Bricks rehearse that feeling at shorter durations so you know what "sustainable" actually looks like.
The structure of the Roadman triathlon bike coaching approach is built around this: train the bike hard enough to race it well, but protect the run by matching brick intensity to phase. Skip the protection, and the bike gains cost you the marathon.
Base-phase bricks (weeks 1–6)
Base phase is about frequency and neuromuscular familiarity, not intensity. The goal is for your legs to stop registering the bike-to-run transition as novel.
Session 1: Short transition brick. 90 minutes on the bike at Zone 2 (65–75% of FTP), followed by a 15-minute run at easy aerobic pace. Do this once a week, mid-week. The run is short enough that it doesn't compromise your weekend long run.
Session 2: Cadence brick. 60 minutes on the bike with the last 20 minutes alternating 2 minutes at 95+ rpm with 2 minutes at 75 rpm. Then 10 minutes running at easy pace, focusing on a high cadence (180+ steps per minute total). This primes the neuromuscular switch.
Session 3: Long ride, token run. Your long aerobic ride of 3–4 hours, followed by 10 minutes of easy jogging. The run is almost symbolic in base phase, but it establishes the habit of lacing up after a long ride. That habit matters more than people think once volume increases.
Keep all base-phase bricks aerobic. The temptation to run hard off the bike is strong because it feels productive. It isn't, not yet. Dan Lorang's approach with his World Tour and long-course athletes has consistently emphasised patience in early blocks — aerobic capacity is the foundation that everything else sits on.
Build-phase bricks (weeks 7–12)
Build phase introduces intensity, but the key is that intensity lives on one side of the brick, not both.
Session 4: Threshold bike, easy run. 2 x 20 minutes at 90–95% FTP on the bike with 10 minutes easy between, total ride 90 minutes. Off the bike, 20 minutes easy running. The bike does the hard work; the run is purely aerobic.
Session 5: Easy bike, tempo run. 2 hours Zone 2 on the bike, then 30 minutes running with the middle 15 minutes at half-marathon pace. This is the first session where the run carries real load, and the easy bike sets it up.
Session 6: Descending brick. 3-hour ride with the final hour at 80–85% FTP, followed by 25 minutes running at marathon pace. This starts teaching the body what target race pace feels like under fatigue, but without the full duration of a race-specific session.
Session 7: Double brick. 45 minutes bike at steady Zone 3, 15 minutes run at tempo, 30 minutes bike at steady Zone 3, 15 minutes run at tempo. This rehearses multiple transitions and builds fatigue resistance in both disciplines simultaneously. Once every two to three weeks is plenty.
One brick per week in early build, two per week by week 10 or 11. Weekend long ride remains the anchor of the programme; bricks serve it, not the other way around.
Race-specific bricks (weeks 13+)
The final six to eight weeks before race day are where brick sessions become the most important workouts in the programme. Every session now rehearses a specific piece of race day.
Session 8: The race-pace rehearsal. 4–5 hours on the bike at Ironman race pace (70–75% of FTP, or whatever your pacing plan specifies), followed by 60–90 minutes running at target Ironman marathon pace. Do this twice in the race-specific block, ideally four and six weeks out. This is the single most predictive session you'll do.
Session 9: Race nutrition brick. 3-hour bike at race pace executing your exact race nutrition plan (90g carbs/hour, specific products, specific bottle timing), followed by 45 minutes running while continuing race-pace fuelling. Tim Spector's work on individual metabolic response underlines that gut training is as specific as any other adaptation. Rehearse the exact plan.
Session 10: The short sharp brick. 75 minutes on the bike with 3 x 8 minutes at 95% FTP, then 20 minutes running with the first 10 at threshold pace. Used in the final three weeks to keep top-end sharpness without accumulating fatigue. Short, specific, leaves you feeling good.
The race-specific phase is where coaching pays for itself. Pacing errors here cost weeks of preparation.
How often to brick and how long to make them
The working dose for most age-group Ironman athletes is one to two bricks per week. One in base, one to two in build, two in race-specific.
Total brick duration — bike plus run — scales with phase. In base, 90–120 minutes total. In build, 2–3.5 hours. In race-specific, 4.5–6.5 hours for the key session, with shorter sharpener bricks at 90 minutes.
The run portion is where most athletes get it wrong. The ratio of run to bike should stay low. For a 5-hour bike, 60–90 minutes of running is plenty. Running longer than 90 minutes off a long ride, unless you've built to it over months, is where injuries happen. Joe Friel has written consistently that durability is built progressively, not heroically.
Place bricks so they don't compromise your long run. If Sunday is long ride plus brick run, the dedicated long run belongs on Wednesday or Thursday, not Saturday.
Mistakes that make bricks counter-productive
Three mistakes show up repeatedly in athlete training logs.
First, running too hard off every bike session. If every brick run is tempo or harder, you accumulate fatigue, compromise the midweek long run, and arrive at race day overcooked. Match intensity to phase.
Second, making bricks too long too early. A 4-hour bike plus 90-minute run in week 6 of a 20-week programme is not base training. It's a race simulation done four months too soon, and it usually produces a stress injury by week 12.
Third, neglecting race nutrition in bricks. The bike leg of an Ironman is where you fuel the marathon. If you haven't rehearsed 90g of carbs per hour on the bike and kept it down through a 60-minute run, you haven't trained for Ironman. You've trained for a long duathlon.
Audit your last four weeks of bricks. Count the sessions, measure the intensity, check the ratio of run to bike. If every run was hard, pull back. If you haven't done a race-pace brick within six weeks of your event, schedule one this weekend.
