Got your place locked in for the London Marathon or another spring marathon? First off—congratulations! Crossing that finish line will be an unforgettable milestone. But right now, sitting in autumn, race day can feel like a world away.
A common trap runners fall into is either diving into intense training far too early (hello, early burnout and overuse injuries) or coasting through winter and realizing in February that they are woefully underprepared.
To help you get the timing spot on, here is your definitive roadmap on when to start formal marathon training and what you should be doing right now to ensure a strong, healthy build-up.
When Does Formal Marathon Training Actually Begin?
For a spring marathon taking place in late April (like the London Marathon), formal, structured marathon training blocks typically run between 16 and 20 weeks.
Counting backward from late April, here is when your official schedule kicks off:
THE MARATHON TIMELINE
[ Autumn ] [ Dec / Jan ] [ April ]
──────┬─────────────────────┬────────────────────┬──────►
BASE-BUILDING FORMAL PLAN RACE DAY
• Easy miles • Structured mileage • Peak performance
• Gear check • Long runs • Taper week
• Foot check-up • Speed & tempo
1. The 20-Week Plan (Starts Early December)
- Best for: First-time marathoners, runners building up after a break, or those who want a lower-stress progression.
- Why it works: The extra 4 weeks give your muscles, tendons, and joints extra time to adapt to higher mileage without sharp spikes.
2. The 16-Week Plan (Starts Early January)
- Best for: Experienced runners or anyone who already maintains a consistent weekly running baseline.
- Why it works: 16 weeks is the sweet spot for peak cardiovascular fitness while keeping mental focus sharp through the cold winter months.
WHAT SHOULD YOU DO RIGHT NOW?
(THE PRE-TRAINING BASE PHASE)
If formal training doesn't kick off until December or January, what should you do between now and day one?
Think of autumn as your foundation-building phase. You shouldn't be running soul-crushing 18-milers yet, but you shouldn't be sitting on the couch either.
1. Build an Aerobic Base (3 to 4 Easy Runs per Week): Keep your runs conversational and manageable. Aim to consistently cover 15–25 miles (25–40 km) a week depending on your level. This strengthens your heart, capillaries, and mitochondria so you can handle formal training without feeling overwhelmed on Week 1.
2. Audit & Optimise Your Running Footwear The shoes you wear for base building are the ones taking you into your high-mileage months. Are your trainers feeling slightly dull, rubbing your toes, or causing arch discomfort? Getting a Free Running Shoe Check-Up early gives you time to assess your footwear's volume, examine pressure points on a force plate, adjust lacing techniques, or introduce proper insoles before mileage ramps up. Definitely need new shoes? Book in for a Run Shoe Selection!
3. Add Strength & Mobility Work (1 to 2 Short Sessions Weekly): Marathons test joint stability as much as endurance. Spend 20 minutes twice a week strengthening your calves, glutes, quads, and ankles. Stronger feet and legs act as natural shock absorbers when long runs start increasing.
4. Get Familiar with Your Pacing Use tools like a Running Pace Conversion Chart to understand your target race paces and easy training zones. Knowing the difference between an easy recovery pace and a tempo effort now will prevent you from running your long training runs too fast later.
The Road Ahead: How Your 16-to-20-Week Block Progresses
Once your formal plan begins in December or January, your training will naturally follow three major phases:
| Phase | Duration | Core Focus |
| 1. Base & Endurance Build | Weeks 1–8 | Gradual increase in weekly volume and weekend long runs. All about building stamina. |
| 2. Peak Mileage & Specificity | Weeks 9–14 | Incorporating marathon-pace intervals, tempo efforts, and peak long runs (18–20+ miles). |
| 3. The Taper | Final 3 Weeks | Reducing mileage by 40–60% while keeping intensity brief, allowing your muscles to repair and fully store glycogen for race day. |
Ready to Start Your Spring Marathon Journey?
Every great marathon performance starts with smart preparation—and having the right expert support makes all the difference.
Whether you're unsure of your current shoes, or need direction on new shoes, specialized running analysis, or tailored 1-on-1 coaching services to fine-tune your form and pacing strategy, our expert team at The Active Foot Co is here to help you move efficiently and stay injury-free throughout your training block.
👉 Explore our full range of Running Analysis & Coaching Services today and get your marathon build-up off to the best possible start!