Brick Workouts in Triathlon: Master the Bike-to-Run

Every triathlete knows the feeling: you step off the bike after the ride leg and your legs feel like concrete. Your stride is short, your heart rate spikes, and race pace seems out of reach. Brick workouts — back-to-back bike and run sessions with no break — are the fix. They are the most specific training session in triathlon and often decide whether you can actually show your run strength on race day. This guide explains how bricks are structured, how often you need them, and which mistakes to avoid.

What is a brick — and why the name?

A brick is a workout that couples two disciplines back to back — classically, cycling followed immediately by running. The name comes from stacking two building blocks ("bricks") on top of each other; some read it as a nod to the "brick legs" feeling after dismounting. Swim-to-bike bricks exist too, but they are far less common because the swim-to-bike transition is physiologically less critical.

The point is not to pile up kilometres but to trigger a specific adaptation: your body learns to switch into an efficient running stride while carrying bike fatigue. This is trainable — and surprisingly fast. After four to six bricks spread over several weeks, most athletes find their running pace after the switch normalises within a few minutes instead of dragging on for a kilometre or more.

The physiology: why legs feel foreign after the bike

The "concrete legs" phenomenon has several causes, and all of them respond to targeted training:

• Muscle recruitment switch. Cycling mainly loads the quads and glutes through a narrow range of motion — concentric work with no impact. Running demands eccentric braking, active hip extension and a functional calf-foot chain. Recruitment patterns have to be completely re-switched.
• Blood redistribution. On the bike, blood is distributed for a seated position. Standing up and running forces the cardiovascular system to re-regulate — heart rate often jumps 10 to 15 beats at the transition without an equivalent rise in actual load.
• Neuromuscular fatigue. After long aerobic pedalling, the ability to run quickly and with coordination is temporarily reduced. Cadence drops, ground contact time lengthens, and running economy measurably worsens.

This is exactly where the brick comes in: it trains the switch as a performance goal of its own. Research on triathlon-specific fatigue shows that experienced triathletes lose far less running economy after cycling than novices — and that advantage comes almost entirely from combined sessions.

How to structure a brick

The good news: the right structure is simple and scales with race distance.

The bike part

The bike leg of a brick is not a time trial. Its purpose is to create realistic bike fatigue — not to destroy you. For most athletes that means an easy-to-moderate ride of 60 minutes (short distance) up to 3 to 5 hours (long distance), mostly in zone 2. If you train with a power meter, aim for 65 to 75 percent of FTP; without one, ride at a conversational but purposeful effort. In the late preparation phase, add blocks at your planned race power — this tests your pacing under realistic conditions.

The transition

The switch itself is part of the workout. Target: under two minutes from bike to running shoes. Lay everything out before the session — shoes, drink, maybe a gel. A fast transition is part of the skill, because this is exactly what you will face in T2 on race day. Use the chance to test your whole setup: lacing system, helmet on or off, race belt.

The run part

Keep it short and controlled: 15 to 25 minutes for sprint and Olympic distance, 20 to 45 minutes for half and full distance. The first 10 minutes almost always feel clunky — that is normal and part of the adaptation. Then steer towards your goal: an easy jog, or in the race-specific phase 10 to 20 minutes at planned race pace. Important: the brick run is not an extra hard run. If you are wrecked after the ride anyway, the bike part was too hard.

How often and when: bricks in the training plan

More is not better. Bricks are demanding because they bundle two sports plus transition stress into one session. A sensible dosage:

• Base phase: A short brick every two weeks (60 to 90 min bike plus 15 to 20 min run), mainly to get used to the switch.
• Build phase: A longer brick every two weeks, with the bike part growing towards race-distance character.
• Race-specific phase (final 8–10 weeks): One brick per week, usually at the weekend as the key session, with race-pace segments and rehearsed fueling.
• The final two weeks before the race belong to the taper — one last short, easy brick 10 to 12 days out is enough as a reminder.

Place the brick so an easy day or a recovery phase follows. Stacking a brick on Saturday and a long run on Sunday piles fatigue on fatigue — the classic route into overload, whose warning signs you should take seriously (overtraining symptoms).

Bricks by race distance

• Sprint (750 m / 20 km / 5 km): 60 to 90 minutes on the bike with 2 to 3 race-pace blocks of 8 minutes, then 15 to 25 minutes of running with 10 minutes at target pace. A fast transition matters more than duration.
• Olympic (1.5 / 40 / 10): 90 minutes to 2:30 on the bike, then 20 to 30 minutes of running. From the build phase, insert 10 to 15 minutes at 10k race pace.
• Half distance (1.9 / 90 / 21.1): 3 to 4 hours on the bike, mostly zone 2 with 2 to 3 blocks at race power, then 30 to 45 minutes of running, partly at half-marathon race pace.
• Full distance (3.8 / 180 / 42.2): 4 to 6 hours on the bike, then 30 to 60 minutes of running. Here the brick doubles as your most important fueling rehearsal — see the full Ironman preparation guide.

Fueling during bricks: the forgotten training goal

A brick is the best dress rehearsal for race nutrition there is. Whatever you eat and drink on the bike has to sit well on the run that follows — and this is exactly where many athletes fail on race day. In the race-specific phase, test systematically: 60 to 90 grams of carbohydrates per hour on the bike, adequate fluids and 400 to 800 milligrams of sodium per hour depending on temperature and sweat rate. If your stomach protests after the switch, reduce intake in the last half hour of the ride or change the gel format. The fundamentals are covered in our guides to fueling and electrolytes.

The five most common brick mistakes

• The bike part is too hard. Riding the bike like a time trial does not simulate a race — it simulates a blow-up. The ride should create race fatigue, not exhaustion.
• The run part is too long and too fast. A 90-minute tempo run after four hours of riding is no longer a brick but a second race, with the recovery bill to match. Keep the run short and controlled.
• Too many bricks. Two or three combined sessions a week create more fatigue than adaptation. One well-placed brick per week is the maximum, even in the race-specific phase.
• Not practising the transition. Showering and having a coffee between bike and run does not train the race transition. Under two minutes from saddle to road — that is the goal.
• No pacing concept. The brick is the perfect chance to calibrate your race-pace feel. After each session, note how the first 10 running minutes felt and which pace proved realistic. That is gold for your race-day planning.

The indoor version: bricks on the trainer

In winter or bad weather, bricks work brilliantly on the indoor trainer — in fact, they become more precise: power targets are exactly controllable, the transition takes seconds, and the run starts on a treadmill or a short loop right outside your door. Many pros deliberately do their race-pace bricks indoors because pacing and fueling can be tested reproducibly there.

How Peakora schedules your bricks

Peakora automatically places combined sessions at the right time in your triathlon plan: short familiarisation bricks in the base phase, weekly key sessions with race-pace segments in the specific phase — matched to your race distance and time budget. The recovery monitor makes sure the brick does not land on an already fatigued week, and the taper scales combined sessions back in time for the start.

Frequently asked questions about brick workouts

How often should you do brick workouts per week?

One brick per week is plenty during the race-specific phase; one every two weeks is enough in the build phase. More adds fatigue without extra adaptation, because combined sessions are demanding and extend recovery time.

How long should the run be after the bike in a brick?

For most athletes, 20 to 45 minutes of running after the ride is ideal. Sprint and Olympic distance athletes often need only 15 to 25 minutes; long-distance athletes can extend it to 60 minutes.

Why do legs feel so heavy after cycling?

Cycling works the muscles concentrically in a limited range of motion, and heart rate runs lower at a given effort. Switching to running forces blood flow, muscle recruitment and stride frequency to readjust — this takes 10 to 15 minutes and can be shortened significantly with regular brick training.

Do I need brick workouts for a sprint triathlon?

Yes, but shorter and more intense. For sprint and Olympic distances, short bricks work well: 60 to 90 minutes of riding with race-pace blocks, then 15 to 25 minutes of running with 10 minutes at target race pace. Transition adaptation matters at every distance.