Ironman Brick with GI Stress Test: Race-Effort Fuelling Session

Session Overview

This session rehearses your full race-day fuelling plan under real fatigue — a long race-effort bike block straight into a race-pace run — so you find out which products and intake rates your gut can handle before race day, not during it. Best used by athletes in the final 6–8 weeks of Ironman-distance build.

What You’ll Need

  • Your full race-day nutrition products (gels, drink mix, chews) at your planned race intake rate
  • A bike computer or power meter to hold race effort
  • A safe, uninterrupted bike route (or turbo setup) plus a run route or treadmill straight afterwards
  • A notebook or notes app to log GI symptoms as they happen

Warm-Up (15 minutes)

15 minutes easy spinning, building gradually so you’re at race effort by the end of the warm-up.

Main Set

A long race-effort bike block, fuelling exactly as planned for race day, straight into a race-pace run with fuelling continuing on schedule.

  • Bike: 2.5–3 hours at roughly 65–75% FTP / race effort, fuelling on schedule from the first 20 minutes at your full target carb intake rate (e.g. 60–90g/hour)
  • Transition: under 5 minutes, exactly as you’d do it on race day — no extended break
  • Run: 40–45 minutes at goal Ironman run pace, continuing your scheduled fuelling
  • Optional harder variation: extend the run to 60 minutes for athletes targeting a sub-10-hour day

Cool-Down (10 minutes)

Easy walk or jog, then rehydrate as normal.

Coaching Notes

  • Log exactly what you ate and drank, when, and any GI symptoms (bloating, nausea, cramping) with a rough severity score — this becomes the basis of your race-day fuelling plan.
  • Run this session at least twice in the final 6–8 weeks before race day, adjusting products or intake rate based on what you learn each time.
  • If something causes distress, don’t just reduce the dose — test whether a different product or format (liquid vs gel vs chew) solves it instead.
  • See our guide to training your gut for Ironman nutrition for the full reasoning behind this session.

Training at your own risk. The information provided is for general guidance only and is not a substitute for professional medical advice. Please consult a doctor before starting any new exercise programme, especially if you have any pre-existing health conditions.