Ironman 70.3 Training: 10 Zone 4 / Threshold Run Workouts
Summary:
These 10 Zone 4 / Threshold workouts target 87–93% of your max heart rate (RPE 7–8) to improve pacing control, stamina and lactate clearance for the half marathon. Ideal for weeks 4–10 of a 12-week plan, these sessions help make race pace feel easier, especially in the final miles when fatigue sets in.
Zone 4 Half Marathon Threshold Workouts
Threshold training builds the strength to run fast without falling apart. These Zone 4 sessions help improve your ability to clear lactate, sustain harder efforts and stay in control when the pace rises. For half marathon runners, that means holding your goal pace longer and finishing strong. This post shares ten Zone 4 workouts designed to sharpen your threshold and boost performance on race day.
Why Zone 4 / threshold Training Matters for the Half Marathon
Success over 13.1 miles isn’t just about mileage, it’s about learning how to stay fast when your legs want to slow down. That’s where Zone 4 / threshold training plays a key role. Threshold running targets the point just below where your body starts to accumulate lactate faster than it can clear it. It’s often described as the hardest effort you can hold for an hour and it trains your body to resist fatigue while maintaining rhythm.
Zone 4 / threshold training develops:
Lactate clearance and buffering
Efficiency at controlled high-end effort
Mental and physical discipline under load
Race-day pacing control at goal pace or just above
Threshold work makes race pace feel smoother and more sustainable. Especially from mile 9 onward, when most runners start to fade.
What Is Zone 4 / Threshold Running?
Zone 4 / threshold, typically falls at:
87–93% of max heart rate
RPE 7–8 (hard but sustainable)
Faster than half marathon pace, slower than 10K pace
Use the FLJUGA calculator to find your zones before starting.
You’ll know you’re in Zone 4 / threshold when talking becomes difficult, but you can still speak in short phrases. It’s “controlled discomfort”, not sprinting, but not relaxing either. Perfect for training that tough, middle ground needed for racing well.
How to Use These Sessions
Include one Zone 4 / threshold session per week during your half marathon build, especially in weeks 4–10 of a 12-week plan. Avoid placing them the day before or after your long run. Always warm up properly and finish with a controlled cool-down. These sessions aren’t about going all-out, they’re about sustaining just-below-redline effort with discipline and precision.
1. Classic Threshold Intervals
Purpose: Establish sustainable high-end aerobic pace
Warm-Up: 15 min jog
Main Set: 4 x 8 min @ Zone 4 (2 min jog between)
Cool-Down: 10 min jog
2. Broken Threshold Blocks
Purpose: Develop mental control and pacing under fatigue
Warm-Up: 15 min jog
Main Set: 3 x (3 min @ Zone 4 + 2 min @ Zone 4 with 60 sec jog between) (2 min jog between sets)
Cool-Down: 10 min jog
3. Threshold Ladder
Purpose: Challenge control across varying durations
Warm-Up: 15 min jog
Main Set: 5 min – 8 min – 10 min @ Zone 4 (2 min jog between)
Cool-Down: 10 min jog
4. Threshold + Tempo Combo
Purpose: Mix intensity to reinforce pacing discipline
Warm-Up: 15 min jog
Main Set: 10 min @ Zone 3 + 10 min @ Zone 4 + 5 min @ Zone 3
Cool-Down: 10 min jog
5. Long Threshold Repeats
Purpose: Build stamina at high aerobic load
Warm-Up: 15 min jog
Main Set: 2 x 15 min @ Zone 4 (3 min jog between)
Cool-Down: 10 min jog
6. Threshold Hill Repeats
Purpose: Combine strength and sustained effort
Warm-Up: 15 min jog
Main Set: 6 x 3 min uphill @ Zone 4 (jog down recovery)
Cool-Down: 10 min jog
7. Double Threshold Day
Purpose: Accumulate Zone 4 volume across two runs
AM Session:
3 x 8 min @ Zone 4 (2 min jog between)
PM Session:
4 x 6 min @ Zone 4 (90 sec jog between)
Each with 10 min warm-up and cool-down
8. Wave Threshold Intervals
Purpose: Improve pacing control under changing loads
Warm-Up: 15 min jog
Main Set: 4 x (2 min @ Zone 3 + 4 min @ Zone 4)
Cool-Down: 10 min jog
9. Long Run with Threshold Finish
Purpose: Simulate end-of-race fatigue
Warm-Up: 10 min jog
Main Set: 60 min @ Zone 2 + 20 min @ Zone 4
Cool-Down: 5 min jog
10. Progressive Threshold Set
Purpose: Teach patience before intensity
Warm-Up: 15 min jog
Main Set: 10 min @ Zone 3 – 10 min @ Zone 4 – 5 min @ Zone 4
Cool-Down: 10 min jog
FAQ: Zone 4 / threshold Training for Half Marathon Runners
What is Zone 4 / threshold training for half marathoners?
Threshold training targets the effort just below your lactate tipping point. It helps you run fast without burning out, sharpening both aerobic and mental fitness. It’s ideal for 10K to half marathon prep.
How often should I do Zone 4 / threshold sessions?
One focused threshold session per week is enough. As race day approaches, you can blend these into longer workouts or combine with pace work.
Can beginners do Zone 4 workouts?
Yes. Just scale the intervals. Beginners can start with 4–6 minutes per rep and build up to longer blocks over time. Always keep effort sustainable.
Do these replace tempo or race pace runs?
Not exactly. Threshold is slightly above race pace, so it complements race pace work rather than replaces it. Think of it as a gear that builds your ability to hold effort longer.
Can I combine Zone 4 and Zone 2 in the same session?
Absolutely. Many sessions in this post do just that, blending threshold intensity into aerobic base runs to simulate real race fatigue.
FURTHER READING: BUILD YOUR HALF MARATHON BASE
Running: Running Zones 1–5 Explained
Half Marathon Training: 10 Zone 3 / Tempo Workouts
Half Marathon Training: 10 Zone 5 / VO2 Max Workouts
Half Marathon Training: 10 Essential Sessions
Half Marathon Training: What Is Zone 4 / Threshold?
Final Thoughts
Threshold training is one of the most effective tools for half marathon success. By consistently training in Zone 4, you’ll improve control, confidence and fatigue resistance, all while making race pace feel more manageable. Choose one of these sessions each week and layer them into your plan for strong, sustainable gains that show up on race day.
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.
