Triathlon Brick Training Calculator

A brick workout is a training session combining two triathlon disciplines back-to-back, most commonly bike followed immediately by run. The term “brick” likely comes from the heavy, leaden feeling in the legs during the run portion, as if they were made of bricks.

Brick training serves two purposes:

1. Physiological adaptation: Training the muscles to switch from the cycling movement pattern (quadriceps-dominant, circular) to running (hamstring and glute activation, linear). That adaptation takes weeks and it is sport-specific. Running fitness on its own does not prepare you for running off the bike.
2. Mental practice: Learning to manage the uncomfortable transition period and pace yourself before your legs “come around” (usually after 1–2 km).

Target paces for brick sessions:

• Bike: 75-85% of race bike speed. This page uses 80%, which sits in the middle and leaves enough in the legs that the run is worth doing. The temptation is always to ride it at race effort, and the run is what pays for that.
• Run: start the first kilometre about 20 seconds per km slower than your race run pace, then let it come down to race pace by roughly the eight-minute mark. The average the calculator reports is worked out from that whole curve, not from a single flat pace, which is why a short brick shows a slower average than a long one at the same effort.

Brick session structures by race distance:

• Sprint prep: 30 min bike + 15 min run, 2× per week in the last 4 weeks
• Olympic prep: 60 min bike + 20 min run, 1–2× per week in last 6 weeks
• 70.3 prep: 90–120 min bike + 30–45 min run, 1× per week
• Ironman prep: 3–4 hr bike + 45–60 min run, 1× per week in peak training

The first brick: expect the run to feel terrible the first few times. That is the normal experience and it improves quickly. Chase smooth turnover rather than pace for the first few sessions and let the speed arrive on its own.