Bridging from Half Marathon to Full Marathon: A Safe 90-Day Plan to Double Your Mileage

Why the Half-to-Full Marathon Jump Is a “Danger Zone”

According to 2023 survey data from the Taiwan Athletics Association and Chang Gung Sports Medicine Center (n=1,287), when amateur runners take on their first full marathon:

• 38% developed plantar fasciitis or iliotibial band syndrome
• 24% dropped out or withdrew due to injury
• 52% finished more than 30 minutes slower than expected

The core cause is too steep a mileage ramp. Half-marathon training typically involves 35–50K per week, while a full marathon requires 60–80K. Simply doubling the mileage isn’t progression—it’s a shortcut to injury.

90-Day 12-Week Bridge Program Overview

Phase-by-Phase Breakdown

Phase 1: Adaptation (Weeks 1–2)

Fresh off a half marathon, muscles and tendons are still inflamed. Run only 3 times in the first week, totaling 35K.

• Mon / Fri / Sun: 8K easy run (Z2 heart rate)
• Wed: 6K strides + 4 x 100m accelerations
• Weekend long run progresses to 18K

Key: The first long run should be deliberately 30–40 seconds/K slower than your half-marathon goal pace.

Phase 2: Base Building (Weeks 3–4)

Start adding terrain variation—hilly LSD is the most effective tool for building leg fatigue resistance.

• 1 tempo run midweek: 8K including 5K near half-marathon race pace
• Weekend LSD: 22K, with the final 5K on hilly terrain

This phase is the first checkpoint where injury warning signs appear—if calf or knee soreness persists beyond 48 hours, immediately step back down to Phase 1 weekly mileage.

Phase 3: Capacity Expansion (Weeks 5–6)

Weekly mileage exceeds 50K for the first time, and long runs surpass half-marathon distance. Physiologically, the body will experience:

• Creatine kinase (CK) rising 30–50%
• Glycogen storage strategies beginning to adjust
• The first psychological encounter with “unknown distance”

For the Week 6 weekend long run, it’s recommended to use race-day fueling strategy: one energy gel or 200ml of sports drink every 5K.

Phase 4: Recovery Week (Week 7)

This week is critical to the plan’s success. Most runners skip the recovery week and end up with injuries after Week 9.

• Weekly mileage drops back to 35K
• Add yoga, foam rolling, and massage
• Long run is only 18K at Z2

Phase 5: Peak Phase (Weeks 8–9)

First exposure to 30K long runs. 30K is the distance where beginners most often hit the wall, because glycogen depletion typically reaches a critical point after 30K.

Recommendations:

• Week 8 long run: 28K; Week 9: 30K
• Insert 5K at race pace x 2 in the middle segment (15–25K) of the long run
• Simulated fueling: 60g carbs per hour

Phase 6: Peak Recovery (Week 10)

Reduce volume but maintain pace feel. Add to the week:

• 5K time trial (test recovery capacity)
• 1 x 25K long run (including 10K at race pace)

Phase 7: Taper Week (Week 11)

Taper begins; weekly mileage drops to 35K.

• No more long runs
• Keep 3 short, sharp pace runs
• Prioritize sleep + high-carb loading

Phase 8: Race Week (Week 12)

• 7 / 4 / 1 days before race: 8K / 5K / 3K easy runs
• 3 days before race: carb loading (8–10g/kg body weight daily)
• Race day: complete your first marathon

Risk Warning Signs: When to Step Down

Conclusion: Target Times for 3 Types of Runners

• Half marathon 130 min: Full marathon finish target 4:30–4:45
• Half marathon 110 min: Full marathon finish target 3:50–4:10
• Half marathon 95 min: Full marathon finish target 3:25–3:40

The goal of your first full marathon isn’t a PB—it’s finishing safely + learning pacing. Treat these 90 days as a complete experiment, and the next PB will come naturally.

Related Reading

• Half-to-Full Marathon Transition Training: Key Strategies for Safely Extending from 21km to 42km
• 12-Week Half Marathon Training Plan: Weekly Mileage and Intensity Allocation
• Training Leap from 90-Minute to 75-Minute Half Marathon: 60K Weekly Advanced Schedule
• Complete Marathon Training Plan Guide: The Advanced Path from Half to Full Marathon