Long Run: 90-Minute Aerobic Base Builder

Session Overview

The long run is the foundation of triathlon run fitness. This 90-minute aerobic base session builds your fat-burning engine, strengthens tendons and connective tissue, and teaches your body to run efficiently when fatigued — exactly what you need coming off the bike in a 70.3 or full Ironman.

What You’ll Need

• GPS watch for pace and distance tracking
• Energy gels or chews (1 gel per 45 minutes of running)
• Hydration vest or handheld bottle for runs over 75 minutes
• Heart rate monitor (recommended to stay in the correct zone)

Warm-Up (10 minutes)

Begin with 10 minutes of very easy jogging — genuinely easy, where conversation flows freely. If you use heart rate, aim for Zone 1 (below 70% max HR). The long run should never start with high intensity; let your joints and muscles warm gradually before settling into your target aerobic pace.

Main Set

The bulk of this session is a continuous aerobic run at strictly controlled intensity. This is NOT a junk miles session — pace and effort control are what make it effective.

• 70 minutes continuous running at aerobic pace (RPE 5–6/10, Zone 2 heart rate: 70–80% of max HR)
• Fuel at the 45-minute mark with a gel and water — don’t wait until you feel hungry
• If you feel the effort creeping above Zone 2, slow down — even walk if needed to keep heart rate controlled

Cool-Down (10 minutes)

Finish with 10 minutes of walk/easy jog, bringing your heart rate down below 120 bpm before you stop completely. Follow with 5 minutes of stretching: focus on hip flexors, glutes, and calves, which take the most load in long running. Drink at least 500ml of water or electrolyte drink in the 30 minutes after finishing.

Coaching Notes

• The most common long-run mistake is going too fast. If you finish feeling good, you’ve done it right. If you finish feeling destroyed, you went too hard and compromised recovery.
• Build long-run duration by no more than 10% per week. If this session is new to you, start at 60 minutes and add 5–10 minutes each week until you reach 90 minutes comfortably.
• Scaling harder: add 4 x 1km at marathon pace in the middle of the main set (minutes 30–50) for a progressive long run variation.
• Run this session once per week, ideally the day after a rest day so you’re fresh. Never run long the day after a hard bike session.