Ironman Bike Training: 10 Threshold Workouts!
What Are Threshold Bike Workouts?
Threshold cycling is a crucial part of Ironman training — it improves sustained power output, pacing efficiency, and fatigue resistance across the 180 km (112-mile) bike leg. These sessions help you ride harder for longer without breaking down, making them essential for building a strong, controlled performance on race day.These sessions focus on Functional Threshold Power (FTP), lactate clearance, and race-specific strength to ensure a strong and efficient ride.
In this post, you’ll find 10 focused threshold bike sessions for building sustained power, control, and race-day strength for Ironman training.
1. Sustained Threshold
Purpose: Build sustained power in Zone 4
Warm-Up: 15 min spin + 3 x 30 sec fast
Main Set: 2 x 20 min @ Zone 4 (5 min easy spin between)
Cool-Down: 10 min easy spin
2. Threshold Intervals
Purpose: Accumulate Zone 4 time with full control
Warm-Up: 15 min spin
Main Set: 4 x 10 min @ Zone 4 (3 min spin between)
Cool-Down: 10 min spin
3. Ladder Threshold Set
Purpose: Build duration and pacing through ascending and descending reps
Warm-Up: 15 min spin + drills
Main Set: 5 / 10 / 15 / 10 / 5 min @ Zone 4 (2 min spin between)
Cool-Down: 10 min spin
4. Alternating Blocks
Purpose: Stress aerobic control with shifts into Zone 4
Warm-Up: 12 min spin
Main Set: 3 x (5 min @ Zone 2 + 10 min @ Zone 4)
Cool-Down: 10 min spin
5. Split Repeats
Purpose: Break threshold into focused chunks to maintain quality
Warm-Up: 15 min spin + 3 high-cadence efforts
Main Set: 2 x (4 min @ Zone 4 + 3 min easy spin + 4 min @ Zone 4)
Cool-Down: 10 min spin
6. Progressive Build
Purpose: Shift from aerobic work into threshold
Warm-Up: 15 min spin
Main Set: 15 min @ Zone 2 + 10 min @ Zone 3 + 10 min @ Zone 4
Cool-Down: 10 min spin
7. Controlled Surges
Purpose: Practice shifting into Zone 4 without losing control of form
Warm-Up: 15 min spin + 3 x 20 sec high cadence
Main Set: 6 x (2 min @ Zone 3 + 3 min @ Zone 4)
Recovery between sets: 2 min spin
Cool-Down: 10 min spin
8. Long Intervals
Purpose: Improve sustained effort under Ironman fatigue
Warm-Up: 15 min spin + cadence work
Main Set: 3 x 15 min @ Zone 4 (5 min easy spin between)
Cool-Down: 10 min spin
9. Threshold Sandwich
Purpose: Combine endurance and threshold in one set
Warm-Up: 10 min spin
Main Set: 30 min @ Zone 2 + 20 min @ Zone 4 + 10 min @ Zone 2
Cool-Down: 10 min spin
10. Threshold Finish
Purpose: Train threshold fatigue resistance late in the ride
Warm-Up: 10 min spin
Main Set: 90 min @ Zone 2 + 20 min @ Zone 4
Cool-Down: 10 min spin
Mini FAQ: Threshold Bike Training for Ironman
What is threshold power on the bike?
Threshold power is the highest average power you can sustain for about an hour—typically measured as Functional Threshold Power (FTP).FLJUGA Training Calculators — set your zones and train smart. Try now.
Why is threshold training important for Ironman cyclists?
It boosts your aerobic capacity, muscular endurance, and ability to hold a steady effort for long periods—crucial for a strong bike split.
How often should I do threshold bike sessions?
Once per week during your build phase is ideal. Combine with long rides, tempo efforts, and recovery rides for balance.
How long should threshold intervals be?
Intervals typically range from 6 to 20 minutes. Start with shorter reps and increase duration as your fitness builds.
Can I do threshold sessions indoors?
Absolutely. Indoor training allows for precise control over intensity and is great for structured threshold work, especially using a smart trainer or power meter.
Final Thoughts
These threshold bike sessions improve sustained power, race-day pacing, and fatigue resistance. Integrate 1–2 per week alongside endurance and recovery rides to maximize your Ironman cycling performance.
Hit these sessions weekly and watch your power, speed, and confidence skyrocket.
Always consult with a medical professional or certified coach before beginning any new training program. The information provided is for educational purposes only and is not a substitute for personalized advice.
