Build phase transitions training from aerobic foundation (base phase) to race-specific fitness. It maintains much of the volume from base while adding quality intensity work.
Key characteristics:
- Moderate-high volume (80-95% of peak)
- Increased intensity
- Race-specific workouts
- Progressive overload
| Goal | How It's Achieved |
|---|
| Raise threshold | FTP/lactate threshold work |
| Develop speed | VO2 Max intervals |
| Race specificity | Simulate race demands |
| Maintain aerobic | Continue Zone 2 volume |
| Intensity | % of Training |
|---|
| Zone 1-2 (Easy) | 70-80% |
| Zone 3-4 (Threshold) | 15-20% |
| Zone 5+ (VO2 Max) | 5-10% |
More intense than base, but easy work still dominates.
| Race Distance | Build Duration |
|---|
| 5K | 4-6 weeks |
| 10K-Half Marathon | 6-8 weeks |
| Marathon/Half Ironman | 8-10 weeks |
| Ironman | 10-12 weeks |
| Day | Workout | Focus |
|---|
| Monday | Recovery | Zone 1-2 |
| Tuesday | Intervals | VO2 Max |
| Wednesday | Endurance | Zone 2 |
| Thursday | Tempo/Threshold | FTP work |
| Friday | Rest or easy | Recovery |
| Saturday | Long + intensity | Race-specific |
| Sunday | Easy endurance | Zone 2 |
| Weeks | Focus | Intensity |
|---|
| 1-2 | Introduction | 2 quality sessions/week |
| 3-4 | Develop | Quality sessions harder |
| 5-6 | Absorb | Recovery week in middle |
| 7-8+ | Race-specific | Peak quality work |
| Workout | Structure | Benefit |
|---|
| Sweet spot | 2×20 min @ 88-94% FTP | FTP with less fatigue |
| Cruise intervals | 4×10 min @ threshold | Threshold tolerance |
| Long threshold | 1×45 min @ 95% FTP | Race simulation |
| Workout | Structure | Benefit |
|---|
| Classic intervals | 5×5 min @ 105-110% FTP | Aerobic ceiling |
| Short/sharp | 8×3 min @ 110-115% FTP | Power at VO2 Max |
| Hill repeats | 6×4 min uphill | Power and specificity |
| Race | Build Workout Example |
|---|
| 5K run | 6×1000m at goal pace |
| Triathlon | Brick workout at race intensity |
| Century ride | 3-hour ride with 60 min @ race power |
| Element | Details |
|---|
| Tempo runs | Weekly, 20-40 min |
| Intervals | 800m-mile repeats |
| Long run | Include race-pace miles |
| Total quality | 15-20% of weekly miles |
| Element | Details |
|---|
| Sweet spot | 2×/week |
| VO2 Max | 1×/week |
| Long ride | Include harder efforts |
| Total quality | 20-25% of weekly hours |
| Element | Details |
|---|
| Bricks | 1-2×/week |
| Sport-specific | Intervals in each discipline |
| Race simulation | Monthly dress rehearsal |
| Balance | Don't neglect weakest discipline |
Build phase creates more fatigue than base. Manage it through:
Every 3-4 weeks, reduce volume and intensity:
| Week Type | Volume | Intensity |
|---|
| Build week | 100% | 100% |
| Build week | 105% | 100% |
| Build week | 110% | 100% |
| Recovery week | 70% | 80% |
| Practice | Benefit |
|---|
| Adequate sleep | 7-9 hours |
| Nutrition timing | Carbs around workouts |
| Easy days truly easy | Don't add junk miles |
| Listen to body | Back off when needed |
| Indicator | What It Means |
|---|
| FTP improving | Threshold rising |
| Can handle more intervals | Fitness adapting |
| Strong in final reps | Good fatigue resistance |
| Race simulations go well | Ready to compete |
| Indicator | What It Means |
|---|
| Can't complete workouts | Too much intensity |
| Chronic fatigue | Need more recovery |
| FTP declining | Overtraining |
| Motivation dropping | Mental fatigue |
Don't jump from base to maximum intensity. Build progressively.
Easy days allow adaptation. Don't turn them into moderate efforts.
Maintain 70-80% easy work. Dropping volume too much hurts aerobic fitness.
Regular rest weeks prevent burnout and allow adaptation.
| Indicator | Ready for Taper |
|---|
| Fitness markers high | Best FTP/times of season |
| Workouts feel hard but manageable | Appropriate fatigue |
| 2-4 weeks until race | Timing right |
| Motivation high | Mentally ready |
| Week | Approach |
|---|
| Final build week | Last hard efforts |
| First taper week | Reduce volume 30%, maintain intensity |
| Race week | Reduce volume 50%+, short sharpening |
Add 2-3 intensity sessions per week, but keep total intensity below 25% of training time.
No—vary workouts to target different systems:
- Week 1: Threshold focus
- Week 2: VO2 Max focus
- Week 3: Race-specific focus
- Week 4: Recovery
Yes—B and C races are excellent training. Don't fully taper; treat them as harder training days.
Consider:
- More recovery
- Different workout structure
- Nutrition optimization
- Sleep quality
