If you've been training for a while, you'll have heard the term "brick session" thrown around. If you're heading into an autumn IRONMAN or 70.3, now is exactly the time to make sure they're a proper fixture in your week — not just an afterthought tacked on when there's time.
What Is a Brick Session?
A brick is simply a bike session followed immediately by a run, with little or no transition time in between. The name comes from the "heavy legs" feeling that catches almost every triathlete out the first time they try it. That feeling is the whole point of the session.
Why Bricks Matter
Cycling and running use overlapping but distinct muscle patterns. After hours in the saddle, your running form, cadence, and perceived effort change — often dramatically. Racing without ever having practised this transition means the first 10-15 minutes of your race run become a costly, unplanned adaptation period rather than controlled effort. Brick sessions train your body (and your head) to handle that shift, so it's familiar rather than alarming on race day.
How to Structure Brick Sessions
Not every brick needs to be a mini-race simulation. Depending on where you are in your training block:
Early-to-mid build: Short, frequent bricks. A 45-60 minute steady ride followed by a 10-15 minute easy run, focused purely on getting the legs used to the transition.
Peak weeks (where most of you sit now): Longer, race-specific bricks. Think a 2-3 hour ride at goal race intensity, straight into a 20-40 minute run at target race pace. This is where you rehearse pacing, nutrition, and mental strategy together, not just fitness.
Race week: Short and sharp only — a 20-30 minute ride with a 5-10 minute run off the bike, just enough to keep the legs sharp without adding fatigue.
Common Mistakes to Avoid
- Skipping the transition practice. Even 60 seconds of simulating a T2 routine (helmet off, shoes changed, race belt on) pays off on race day.
- Going too hard on the bike, every time. If every brick is a bike time trial, you'll burn out before race day. Save max-effort bricks for key sessions only.
- Doing bricks in isolation from the rest of your week. Fit them where they make sense in your overall training load — this is exactly the kind of periodisation we build into every athlete's plan.
Bringing It Together
Brick sessions are one of the simplest, highest-return additions you can make to an autumn race build. If you're not sure how to fit them into your week without overloading, our 1-2-1 coaching builds this in from day one around your life, not a generic template. Training for your first 70.3 or full? Our guide on how to train for your first IRONMAN 70.3 covers where bricks fit into the bigger picture.
Want a second opinion on your current plan? Get in touch for a free consultation.
Coach Ross