Triathlon••7 min read
20-Week Half Ironman Training Plan
Extended 20-week 70.3 training plan with gradual progression. Perfect for beginners or athletes returning from a break who need extra base building time.
A 20-week Half Ironman training plan provides extended base building for athletes new to long-course triathlon or those returning from a training break.
The extra four weeks compared to a 16-week plan allow for more gradual volume increases, reducing injury risk and building a stronger aerobic foundation for the 1.9km swim, 90km bike, and 21.1km run.
Who Should Choose 20 Weeks?
Ideal Candidates
- First-time 70.3 athletes
- Those new to endurance sports
- Athletes returning from injury or extended break
- Anyone with limited triathlon background
- Those concerned about injury risk
- Busy professionals who need flexible buildup
When 16 Weeks is Sufficient
- Experienced Olympic distance racers
- Athletes with strong single-sport background
- Those with solid aerobic base already
- Previous 70.3 finishers
Training Plan Structure
5-Week Block Approach
| Block | Weeks | Phase | Focus |
|---|---|---|---|
| 1 | 1-4 | Foundation | Basic fitness, routine |
| 2 | 5-8 | Base Building | Aerobic development |
| 3 | 9-12 | Build 1 | Volume increase |
| 4 | 13-16 | Build 2 | Race-specific fitness |
| 5 | 17-20 | Peak & Taper | Final preparation |
Weekly Volume Progression
| Week | Hours | Phase |
|---|---|---|
| 1-2 | 6-7 | Foundation |
| 3-4 | 7-8 | Foundation |
| 5-6 | 8-9 | Base |
| 7-8 | 8-9 | Base (recovery at 8) |
| 9-10 | 9-10 | Build 1 |
| 11-12 | 10-11 | Build 1 (recovery at 12) |
| 13-14 | 10-11 | Build 2 |
| 15-16 | 11-12 | Build 2 (recovery at 16) |
| 17-18 | 12-13 | Peak |
| 19-20 | 7-8 → 5-6 | Taper |
Block 1: Foundation (Weeks 1-4)
Goals
- Establish consistent training routine
- Build basic fitness in all three sports
- Learn proper technique
- Develop good habits
Sample Week (Week 3, ~7.5 hours)
| Day | Session | Duration | Intensity |
|---|---|---|---|
| Mon | Swim technique | 40 min | Easy |
| Tue | Easy run | 35 min | Zone 2 |
| Wed | Rest | - | - |
| Thu | Easy bike | 60 min | Zone 2 |
| Fri | Swim endurance | 35 min | Easy |
| Sat | Long bike | 90 min | Zone 2 |
| Sun | Long run | 50 min | Zone 2 |
Key Focus Areas
- Swimming: Technique drills, building comfort
- Cycling: Saddle time, bike handling
- Running: Easy, consistent miles
- All disciplines: Zone 2 effort
Block 2: Base Building (Weeks 5-8)
Goals
- Increase aerobic capacity
- Extend session duration
- Introduce first brick workouts
- Build confidence
Sample Week (Week 6, ~8.5 hours)
| Day | Session | Duration | Intensity |
|---|---|---|---|
| Mon | Swim technique + endurance | 50 min | Easy-Moderate |
| Tue | Easy run | 45 min | Zone 2 |
| Wed | Bike endurance | 75 min | Zone 2 |
| Thu | Rest | - | - |
| Fri | Swim endurance | 40 min | Easy |
| Sat | Brick: Bike + Run | 100 + 20 min | Easy |
| Sun | Long run | 55 min | Zone 2 |
Week 8: Recovery Week
Reduce volume by 30-40%:
- Shorter sessions
- All easy intensity
- Extra rest day if needed
- Mental and physical reset
Learn why recovery is essential: Triathlon Periodization Explained
Block 3: Build 1 (Weeks 9-12)
Goals
- Introduce threshold training
- Extend long sessions significantly
- Practice race nutrition
- Build race-specific fitness
Sample Week (Week 10, ~10 hours)
| Day | Session | Duration | Intensity |
|---|---|---|---|
| Mon | Swim CSS intervals | 50 min | Hard |
| Tue | Run tempo | 50 min | Moderate-Hard |
| Wed | Bike tempo | 80 min | Moderate |
| Thu | Easy swim | 40 min | Easy |
| Fri | Rest | - | - |
| Sat | Long brick | 2.5 hrs + 30 min | Race effort |
| Sun | Long run | 70 min | Zone 2 |
Key Workouts
Swim CSS Set:
Warm-up: 300m easy
Main: 5 x 200m at CSS pace, 15s rest
Cool-down: 200m
Use our CSS Calculator to find your pace.
Bike Tempo:
Warm-up: 15 min
Main: 2 x 20 min at 85-90% FTP, 5 min easy
Cool-down: 10 min
Block 4: Build 2 (Weeks 13-16)
Goals
- Race simulation workouts
- Longest training sessions
- Fine-tune nutrition strategy
- Build confidence for race day
Sample Week (Week 14, ~11 hours)
| Day | Session | Duration | Intensity |
|---|---|---|---|
| Mon | Swim threshold | 55 min | Hard |
| Tue | Run intervals | 55 min | Hard |
| Wed | Bike sweet spot | 90 min | Moderate-Hard |
| Thu | Easy swim | 45 min | Easy |
| Fri | Rest | - | - |
| Sat | Race simulation brick | 3 hrs + 45 min | Race effort |
| Sun | Long run (progressive) | 85 min | Building |
Long Session Targets
| Week | Long Bike | Long Run | Brick Run |
|---|---|---|---|
| 13 | 3 hours | 80 min | 40 min |
| 14 | 3.5 hours | 85 min | 45 min |
| 15 | 3.5 hours | 80 min | 45 min |
| 16 | 2.5 hours | 65 min | 30 min (recovery) |
Block 5: Peak & Taper (Weeks 17-20)
Weeks 17-18: Peak
Highest training volume with race simulation:
| Day | Week 17 | Week 18 |
|---|---|---|
| Sat Brick | 4 hrs bike + 50 min run | 3.5 hrs bike + 45 min run |
| Sun Long Run | 100 min | 90 min |
Weeks 19-20: Taper
Week 19:
- 60% of peak volume
- Maintain some intensity
- Focus on rest and recovery
Week 20 (Race Week):
- 40% of peak volume
- Easy sessions only
- Mental preparation
- Final gear checks
See our complete Triathlon Taper Guide.
Training Tips for Success
Nutrition Practice
Start practicing race nutrition from Week 5:
- Same products you'll use on race day
- Same timing and amounts
- Note any GI issues
- Adjust as needed
Read more: Half Ironman Nutrition Plan
Recovery Management
With 20 weeks of training:
- Recovery week every 4th week
- Listen to your body
- Prioritize sleep (7-9 hours)
- Don't add extra sessions
Pacing Discipline
For 70.3 success:
- Bike at 70-75% FTP (not 85%!)
- Start run conservatively
- Save energy for second half of run
Learn more: Half Ironman Pacing Strategy
Why Extended Base Works
Research Findings
A longer aerobic base phase:
- Improves fat oxidation capacity
- Builds more mitochondria
- Creates lasting fitness adaptations
- Reduces overtraining risk
- Improves heat adaptation
Practical Benefits
- More time to build long sessions gradually
- Lower injury risk from rapid volume increases
- Better technique development
- More confidence on race day
- Flexibility for life interruptions
Estimate Your Race Time
Use our 70.3 Calculator to predict your finish time based on training paces.
Related Resources
- 16-Week Half Ironman Plan - Shorter alternative
- 24-Week Half Ironman Plan - Even more gradual build
- Half Ironman First Timer Guide - Complete beginner guide
- Triathlon Base Building - Foundation phase details
- Half Ironman Glossary - Key terms explained