The short answer
A brick workout is a bike ride followed straight away by a run, with no rest in between. It exists to rehearse the heavy, wobbly feeling in your legs when you start running after cycling, which is exactly what T2 feels like on race day. For race prep, one or two short bricks in the last month are enough to know what to expect.
Why the first minutes of the run feel so strange
After a long ride your legs have spent an hour or more turning a circle at 80 to 100 rpm, and then you ask them to run. Your stride is short and your pace feels higher than it is. For most people it passes within the first 5 to 10 minutes of the run (an estimate, it varies a lot).
The research is thin but points the same way. A small 2010 study of 12 athletes found that brick sessions made knee movement more adaptable when switching from cycling to running. A thesis comparing runners, cyclists and triathletes found that triathletes kept their running economy after cycling while the other two groups lost it, and that athletes more used to the transition rated it as easier. Neither measured race results, so treat the effect as real but modest. The bigger win is psychological: you stop panicking about the feeling.
How long to make a brick
For race prep, short beats long. These lengths are estimates drawn from common coaching practice, not from a trial:
| Your race | Bike | Run straight after |
|---|---|---|
| Sprint | 30 to 45 min | 10 to 15 min |
| Olympic | 45 to 75 min | 15 to 20 min |
| Half | 90 to 150 min | 20 to 30 min |
| Full | 2 to 4 hours | 20 to 30 min |
Ride the last part at around the effort you plan to race, then change shoes quickly and run the first kilometres slower than you want to. The point is to learn what a controlled start to the run feels like. Time your change with the transition time calculator so the practice includes the real thing: helmet off, shoes on, go.
Where a brick fits in the last weeks
A sensible pattern, again an estimate: one brick about 3 to 4 weeks out as a longer rehearsal, a second about 10 to 14 days out as a shorter one at race effort, and none in the final week. In the last week your job is to arrive fresh, which is what the taper calculator is for, and the race week checklist covers the rest.
Use the brick as a dress rehearsal for everything else too. Eat and drink what you plan to race with (see triathlon nutrition basics), wear the tri suit and the race shoes, and lay out a mock transition. Anything that rubs, flaps or upsets your stomach in a brick will do it on race day.
Common brick mistakes
- Running too fast too soon. The first kilometre after the bike always reads fast on your watch, so go by effort, not pace.
- Making every brick long. A long brick late in the build costs recovery you need.
- Skipping it entirely. Not knowing what T2 feels like is a common first-timer surprise. See your first triathlon for the others.
Sources
- Haworth et al., Training for the bike to run transition in triathlon, ISBS Conference Proceedings, 2010 (12 athletes, brick vs single-sport training)
- Rhodes University thesis on running economy after cycling in runners, cyclists and triathletes
- Session lengths and timing in the table and the third section are estimates from common coaching practice, not a published trial
Published 2026-10-20. Your race's athlete guide always has the final word on its rules and times.
Questions
What does brick mean in triathlon?
A brick is a bike session followed immediately by a run, so your legs practise the switch from cycling to running. The name is usually explained by how your legs feel at the start of the run.
How long should a brick workout be?
For race prep, keep it short: roughly a 30 to 45 minute ride and a 10 to 15 minute run for a Sprint, rising to a 90 to 150 minute ride and a 20 to 30 minute run for a Half. These are estimates, not rules.
How many brick workouts do I need before a race?
One or two is enough for most first-timers: one about 3 to 4 weeks before the race and a shorter one about 10 to 14 days before. Skip bricks in race week so you arrive fresh.
Why do my legs feel like jelly after the bike?
Your legs have been turning a fixed circle for a long time, and running asks them for a different movement. The feeling usually fades within 5 to 10 minutes of running, and practising the transition shortens it.
Do I need a brick workout for a Sprint triathlon?
It is not essential, but one short brick removes the biggest surprise of race day. A 30 minute ride followed by a 10 minute run is plenty.