Aerobic Base Builder: 75-Minute Easy Run for Triathlon Training

February and March are prime base-building months for UK triathletes. This 75-minute easy run is designed to build your aerobic engine without accumulating excessive fatigue — keeping you fresh for other training sessions. Consistency over intensity is the foundation of triathlon fitness, and this session exemplifies that principle.

Session Overview

• Duration: 75 minutes
• Location: Outdoor
• Type: Endurance
• Level: Beginner to Intermediate
• Effort: Zone 2 (conversational pace)
• Estimated distance: 10–13km depending on pace

What is Zone 2 Running?

Zone 2 is your conversational aerobic pace — an effort level where you could hold a full conversation without gasping. On a heart rate basis, this is typically 65–75% of your maximum heart rate. It feels deceptively easy, but consistent Zone 2 running builds the aerobic base that underpins all your faster training.

Many triathletes run too hard on easy days, turning Zone 2 runs into Zone 3 slogs. Resist the temptation to push — the adaptations happen at low intensity.

Session Structure

Minutes 0–10: Warm-Up

Begin at very easy walking pace for 2 minutes, then transition into a gentle jog. Keep pace below your Zone 2 ceiling for the first 10 minutes to allow your heart rate to stabilise and your joints to warm up. This is especially important in cold February weather.

Minutes 10–65: Main Run

Settle into your Zone 2 pace — conversational, controlled, and consistent. If running on hilly terrain, slow down on inclines to maintain heart rate (rather than maintaining pace and spiking heart rate). Use a flat or gently rolling route where possible for true aerobic base building.

• Heart rate target: 130–150bpm (adjust for your age and fitness)
• RPE: 4–5 out of 10 — comfortable, not challenging
• Check in every 15 minutes: can you still hold a conversation?

Minutes 65–75: Cool-Down

Reduce pace to an easy jog and finish the final 5 minutes at walking pace. Perform 5 minutes of static stretching post-run: calves, quads, hip flexors, and hamstrings.

How Often to Run This Session

Include one 75-minute easy run in your weekly training block throughout the base-building phase (January–March). It can be performed the day after a harder session (turbo intervals, threshold swim) as it is gentle enough to allow recovery while still adding aerobic volume.

Base-Building Tips for February

• Do not increase weekly run volume by more than 10% per week
• Track duration rather than pace in base phase — time on feet matters more than speed
• Prioritise consistency — five easy sessions per week beats one hard session
• Add a longer run every 2–3 weeks to build endurance