Double Brick Session: Swim-Bike-Run-Bike-Run Ironman Simulation

Session Overview

A swim-bike-run-bike-run “double brick” that rehearses the specific fatigue pattern of racing on tired legs twice over, building the neuromuscular adaptation to run off the bike more effectively than a standard single brick session.

What You’ll Need

• Access to a pool or safe open water for the swim segment (or substitute a 15-minute steady turbo spin if swimming isn’t practical that day)
• Bike, helmet and running shoes staged together for fast transitions
• Race-day nutrition to practise fuelling between legs

Warm-Up (10 minutes)

10 minutes easy swimming or spinning to raise heart rate gradually before the structured work begins.

Main Set

Complete the full sequence back to back with minimal transition time, simulating race-day changeovers:

• Swim 20-30 minutes at steady aerobic effort
• Bike 60 minutes at race-pace effort (roughly 70.3 or Ironman intensity, not all-out)
• Run 15 minutes off the bike at an easy, controlled pace — focus on finding rhythm rather than speed
• Bike 30 minutes at race-pace effort
• Run 20 minutes off the bike, allowing pace to settle naturally as your legs adapt

Cool-Down (10 minutes)

10 minutes easy walking or gentle spinning, followed by rehydration and a recovery snack — this session creates real fatigue, so treat recovery seriously.

Coaching Notes

• The first few minutes of each run segment will feel heavy and awkward — that “jelly legs” sensation is exactly what this session is training your body to adapt to.
• Common mistake: riding both bike segments too hard. This session is about accumulating race-realistic fatigue, not testing your bike FTP.
• Practise your transitions with real urgency, not casually — the changeover speed itself is a skill worth training.
• Scaling: newer athletes can drop to a single bike-run brick at the same intensities and build up to the full double brick over several weeks as fitness allows.