Build Phase Training for Triathletes
Convert aerobic base into race-specific fitness
The build phase sits between base and peak. Volume plateaus or drops slightly while intensity climbs. This is where you start looking — and feeling — race-ready.
What Changes in the Build Phase
- • Intensity goes up: tempo, threshold, and VO2 work enter the plan
- • Sessions become more race-specific (race-pace intervals, open-water swims, brick workouts)
- • Strength shifts from foundational to power-focused
- • Nutrition and pacing start being rehearsed in longer workouts
Duration by Race Distance
| Race Distance | Build Length | Weekly Hours |
|---|---|---|
| Sprint | 3–4 weeks | 5–7 hours |
| Olympic | 4–6 weeks | 7–10 hours |
| Half Ironman | 6–8 weeks | 10–14 hours |
| Full Ironman | 8–12 weeks | 12–18 hours |
Key Workout Types
Threshold intervals
2 × 20 minutes at threshold pace (comfortably hard) with 5 minutes easy between. Builds lactate clearance.
Tempo efforts
30–60 minutes at "hard but sustainable" — the pace you could hold for a 10km race. Raises your sustainable race pace.
Brick workouts
Bike immediately followed by run, 2× per week. The single best session for triathlon-specific adaptation.
Race-pace long workouts
A long ride or long run where the middle portion is held at goal race pace. Teaches pacing and builds confidence.
Sample Build Week (Half Ironman)
- Monday: Rest / mobility
- Tuesday: Swim 60 min (threshold sets) + easy run 30 min
- Wednesday: Bike threshold intervals 75 min
- Thursday: Run tempo 60 min + swim drills 30 min
- Friday: Easy bike 45 min + core
- Saturday: Long ride 3–4 hours with race-pace middle hour
- Sunday: Brick: 90 min bike + 40 min run
Managing Fatigue
The 3:1 rule
Three weeks of progressive load, one week of deload (20–30% less volume, no hard sessions). Prevents overreaching.
Sleep is a workout
When volume goes up, sleep must too. Aim for 8+ hours. Adaptation happens during recovery, not during the session.
Red flags
Elevated resting HR, poor sleep, persistent heavy legs, or low motivation for 3+ days = cut intensity and take an extra rest day.
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Try a calculator
- Triathlon Training Plan Generator
Generate the full plan so you know exactly how much build phase you have.
- Triathlon Race Time Calculator
Check whether your build-phase paces are tracking toward your goal time.
Other Training Phases
Where build fits into the full season