Marathon Pace Run: 15km at Race Effort

Session Overview

This 15km threshold run at marathon race effort is a key session for IRONMAN build training. Running at the pace you intend to hold for your IRONMAN run leg (approximately 26-mile equivalent pace) trains the specific aerobic and muscular systems needed for long-distance racing. This session should feel controlled but challenging — sustainable, not comfortable.

What You'll Need

• GPS watch with pace display
• Running shoes (ideally your race shoes to check fit and feel)
• 1–2 gels if testing race nutrition
• Water or sports drink (especially if it's warm)

Warm-Up (15 minutes)

Jog 2km easy at a fully conversational pace (RPE 3–4). Follow with dynamic drills: leg swings, high knees, heel flicks, and 4 x 80m strides at close to your target pace. The strides prime your neuromuscular system for the pace effort ahead without generating pre-fatigue.

Main Set

Run 15km at your target IRONMAN marathon pace — RPE 7/10. This equates to approximately 80–85% of maximum heart rate. You should be working hard enough to make conversation difficult but not impossible in short sentences.

• 0–5km: Settle into pace. Resist the urge to run faster than planned in the first 3km — early speed costs you disproportionately in the final third.
• 5–10km: Maintain pace, stay relaxed in the shoulders and hands. Check your cadence every 2km — aim for 170–180 steps per minute.
• 10–15km: Stay disciplined. If your pace is drifting, it's a sign your target pace is too aggressive — adjust for next time. If you feel strong, maintain (don't accelerate).
• Optional: Take one gel at 8km to practice mid-run fuelling

Cool-Down (10 minutes)

Jog 1km easy, then walk 5 minutes. Complete calf stretches, quad stretches, and hip flexor holds (60 seconds each side). This session creates significant muscular fatigue — take an easy or rest day the following day.

Coaching Notes

• Run this session fresh — not after a hard bike day. The quality of this session depends on arriving with adequate glycogen and muscle recovery.
• Your IRONMAN run pace should be approximately 30–45 seconds per km slower than your standalone half marathon pace. Don't set your target based on road race pace.
• Easier variation: 10km at marathon pace for athletes early in their training build.
• HR zone target: Zone 3–4 (approximately 75–85% max HR) throughout.