Heat Brick: Bike-to-Run Race-Week Heat Acclimatisation Session

Session Overview

A combined bike-to-run session designed to rehearse racing in late-summer heat: a controlled-effort ride straight into an off-the-bike run, done in the warmest part of the day you can safely train in. It’s for anyone with a hot-weather race coming up who wants their body — and their pacing discipline — used to running on tired legs in the heat before race day.

What You’ll Need

• Bike set up as close to race position as possible
• Race-day nutrition and hydration (test what you’ll actually use on race day)
• Running shoes and kit staged for a fast transition
• A route or turbo session in direct sun or the warmest available conditions — optional but recommended if racing in heat

Warm-Up (10 minutes)

10 minutes easy spinning to raise core temperature gradually rather than starting the main set cold — in heat, your body is already working to cool itself, so there’s no need to force the warm-up.

Main Set

Ride at your target race-pace effort (roughly 75-80% of threshold for a 70.3-style effort, adjust for your target distance), then transition straight into a run at your intended race pace. Focus on hitting your fuelling and hydration plan exactly as you would on race day — heat sessions are where nutrition mistakes show up fastest.

• 40 minutes bike at steady race-pace effort, fuelling every 15-20 minutes as planned for race day
• Quick transition (aim for under 90 seconds — this is also transition practice)
• 15 minutes run off the bike at intended race pace, focusing on form as fatigue and heat both build

Cool-Down (10 minutes)

Walk or jog easy for 5-10 minutes, then rehydrate deliberately — weigh yourself before and after if you can, since post-session weight loss is the simplest way to estimate your sweat rate and refine your race-day fluid plan.

Coaching Notes

• Heat sessions increase cardiovascular strain even at “easy” paces — if you feel dizzy, stop sweating, or your heart rate climbs well above normal for the effort, stop and cool down immediately.
• Don’t do your first-ever heat session the week of a hot race — heat adaptation takes 7-14 days of repeated exposure to build meaningfully.
• Scaling down: shorten the bike to 20-25 minutes and the run to 10 minutes if this is your first heat brick.
• Scaling up: repeat the bike-run block twice with a short recovery between for a race-simulation version closer to sprint or Olympic distance.