5-Hour Ironman Bike Simulation Session

Session Overview

This 5-hour ride simulates the bike leg of a full IRONMAN and is one of the most demanding — and important — sessions in long-course training. Beyond building raw cycling endurance, this session trains your ability to pace over extended duration, tests your nutrition strategy at race intensity, and conditions your body to the physical demands of sitting in an aero position for hours. Schedule this session 8–10 weeks before your A-race, with sufficient recovery days either side.

What You'll Need

• Road or triathlon bike, fully maintained and race-ready
• Nutrition: aiming for 300–400 calories per hour (gels, bars, rice cakes, or liquid calories)
• Electrolyte drink — minimum 500ml per hour, more in warm weather
• Spare tube, tyre levers, CO₂ inflator
• GPS cycling computer with power meter if available
• Sunscreen, arm warmers or gilet for variable UK conditions

Warm-Up (20 minutes)

Begin with 20 minutes easy riding at zone 1–2 (RPE 3–4) to warm muscles and let heart rate settle. Include 4 x 30-second low-gear seated climbing efforts to engage glutes and prime the power systems. Then transition to your race position.

Main Set

Ride 4.5 hours at IRONMAN bike pace — RPE 6–6.5, approximately 65–70% of FTP. Keep the effort controlled throughout. The goal is to arrive at the 5-hour mark having conserved enough for a quality run, not to set a cycling PB.

• Hours 1–2: Settle into rhythm at 65–68% FTP. Resist pushing into zone 3 on climbs — back off, shift down, spin over hills.
• Hours 2–4: Maintain steady power. This is where discipline is tested. Eat and drink every 20 minutes regardless of hunger or thirst.
• Hours 4–5: If feeling good, you can edge up to 70% FTP. Avoid surging — consistency beats heroics.
• Throughout: Stay in aero position for as much of the ride as possible. Your goal is to run off this effort — practice that discipline now.

Cool-Down (15 minutes)

Spin the final 15 minutes in an easy gear, gradually reducing effort. Stretch hip flexors, glutes, and calves immediately after dismounting — extended aero position causes significant hip flexor tightening. Consume 60–90g carbohydrate with 20–25g protein within 30 minutes of finishing.

Coaching Notes

• This session is a nutrition rehearsal as much as a fitness session. Log exactly what you consumed, when, and how your gut responded. Refine the strategy for your next long ride.
• If you have access to a power meter, normalised power (NP) for the ride should be at or slightly above average power — high VI (Variability Index above 1.10) indicates too much surging on hills.
• Easier variation: 3.5 hours for athletes in their first IRONMAN build block.
• Do not run immediately after this session. Conduct a 10-minute walk only to assess legs, then save any run volume for the following day's short recovery jog.