Triathlon requires your body to run on legs that were just cycling. Brick training rehearses that switch before the start line — and shows whether your Race Pacing Targets on the bike leave enough run for the second half. That is a neuromuscular switch problem, not a fitness gap — and it is what bricks are designed to solve. For T1/T2 kit and transition layout on race day, see Your First Triathlon Explained.
Why bricks
Why Legs Feel Like Bricks
Cycling favours quads and a shorter hip range. Running needs glutes, longer stride, and a different kinetic chain. For 30 seconds to several minutes your nervous system still fires for cycling — you run inefficiently until the pattern updates.
More rehearsed transitions mean faster normalization. That is the entire point of brick training.
Definition
What a Brick Session Is
Two disciplines back-to-back with minimal rest. In racing, legs go swim → bike → run; in training, bike → run bricks deliver the most run-specific adaptation. Swim → bike sessions help T1 rhythm with less carry-over to the run.
On WattX, brick sessions are built into your WattX Race Plan PRO — scheduled in base, build, and peak phase according to the distance you are training for.
Formats
Brick Formats
Endurance ride → endurance run.
Builds fatigue on the bike, then teaches pacing on heavy legs. Most common in base.
Quality for build and peak — not base. Rehearse race-day leg feel.
4 × (10 min bike / 3 min run).
Many switches per hour — neuromuscular learning for Olympic and sprint.
70.3 ~3 h → 60 min run · IM ~4 h → 2 h run.
Long-course specificity; highest recovery cost of the week.
Scheduling
Scheduling in Your Week
Olympic / sprint: base — short neuromuscular brick; build — multi-repeat (10/3); peak — race simulation brick.
See Race Planning Explained for how phases fit the full plan.
Practice real transition flow when you can — the clock includes T2.
A WattX Race Plan PRO slots brick sessions into the right weeks by phase and distance.
Mistakes
Common Mistakes
Cycling legs make pace feel easier. Hold [Training Zones](/guides/triathlon-training-zones) or power until stride normalizes.
20 minutes often suffices off the bike. Save long runs for standalone endurance sessions.
Start at least 8 weeks out for 70.3 — the switch needs repetition.
One per week is plenty for most age-group athletes.
Pacing tie-in
Tie-In to Pacing and Analysis
Bricks rehearse the same percentages as your Race Simulator and Race Pacing Targets.
After race day, Race Analysis Explained shows whether your brick work translated — or whether the bike was still too hot.
Keep CSS, FTP, and FT up-to-date on our Test tool — or sync from a clean race in the Race Vault. Protocols: How to Test Your Thresholds.