Marathon Run Training: 10 Threshold Sessions
SUMMARY:
Threshold running (87–93% max HR, RPE 7–8) helps Ironman athletes build sustained speed, pacing control and fatigue resistance. By targeting your lactate threshold, these sessions improve your ability to run strong in the final miles. This post includes 10 Zone 4 workouts designed to boost form, focus and finishing strength on race day.
What Is Threshold Running in Ironman Training?
Threshold running is critical in Ironman training as it helps build sustained speed, endurance, and efficiency while improving your ability to clear lactate and maintain a strong pace deep into the marathon.
These workouts train your body and mind to hold form under fatigue, manage effort more precisely and stay strong through the later miles when most athletes fade. With the right threshold sessions, you’ll build the resilience to run with control — not just survive the marathon, but finish it strong.
In this post, you’ll find 10 threshold run sessions designed to build sustained speed, pacing control, and marathon strength for Ironman race day.
Threshold Run Metrics (Zone 4)
Use these training zone markers to guide your threshold sessions:
Heart Rate: 87–93% of max HR
Effort (RPE): 7–8 — hard but sustainable
Pace: Your threshold pace — the fastest pace you can hold for 45–60 minutes
Breathing: Laboured, but controlled — speaking is limited to short phrases
Form Cue: Focused posture, smooth cadence, and rhythm under pressure
Use FLJUGA’s free Heart Rate and Threshold Calculators to dial in your personalised training zones.
1. Straight Tempo Threshold
Purpose: Sustain uninterrupted time in Zone 4
Warm-Up: 15 min easy jog
Main Set: 20 min @ Zone 4
Cool-Down: 10 min jog
2. Cruise Intervals
Purpose: Break threshold work into manageable repeats
Warm-Up: 12 min jog + 4 strides
Main Set: 4 x 8 min @ Zone 4 (2 min jog recoveries)
Cool-Down: 10 min jog
3. Broken Threshold Ladder
Purpose: Build cumulative Zone 4 load with changing durations
Warm-Up: 15 min jog + drills
Main Set: 5 min / 10 min / 15 min / 10 min / 5 min @ Zone 4 (2 min recovery jogs)
Cool-Down: 12 min jog
4. Alternating Threshold Blocks
Purpose: Teach pace control within Zone 4
Warm-Up: 12 min jog
Main Set: 3 x (3 min easy + 9 min @ Zone 4)
Cool-Down: 10 min jog
5. Split-Set Threshold
Purpose: Divide a long rep into short, manageable chunks
Warm-Up: 12 min jog
Main Set: 3 x (4 min + 2 min) @ Zone 4 (1 min between reps)
Cool-Down: 10 min jog
6. Progressive Threshold Build
Purpose: Increase effort gradually into Zone 4
Warm-Up: 15 min jog
Main Set: 10 min @ Zone 2 + 10 min @ Zone 3 + 5 min @ Zone 4
Cool-Down: 10 min jog
7. Threshold Fartlek
Purpose: Build Zone 4 time with unstructured rhythm
Warm-Up: 12 min jog + 3 strides
Main Set: 8 x 3 min @ Zone 4 (1 min jog between)
Cool-Down: 10 min jog
8. Long Repeats
Purpose: Extend duration of Zone 4 intervals
Warm-Up: 15 min jog + drills
Main Set: 3 x 12 min @ Zone 4 (3 min jog recoveries)
Cool-Down: 12 min jog
9. Threshold Sandwich
Purpose: Combine easy and threshold for real-world pacing control
Warm-Up: 10 min jog
Main Set: 15 min @ Zone 2 + 15 min @ Zone 4 + 10 min @ Zone 2
Cool-Down: 10 min jog
10. Marathon-Specific Threshold Finish
Purpose: Train fatigue resistance at threshold
Warm-Up: 10 min jog
Main Set: 30 min @ Zone 2 + 20 min @ Zone 4
Cool-Down: 10 min jog
Mini FAQ: Threshold Run Workouts for Ironman
What is threshold pace in running?
Threshold pace is the fastest pace you can sustain for about an hour—comfortably hard, but just below the point where fatigue rapidly builds.
Why are threshold sessions important for Ironman athletes?
They improve your lactate clearance, running efficiency, and mental strength—especially critical for staying strong in the final miles of the marathon.
How often should I include threshold runs?
Once per week is ideal during your build phase. Combine with aerobic and long run sessions for a balanced program.
What’s a typical threshold run session look like?
Example: 10-minute warm-up, 4 x 5-minute intervals at threshold pace with 90 seconds jog recovery, followed by a 10-minute cool-down.
Can beginners do threshold workouts?
Yes—just scale the intervals to your fitness level. Start with shorter reps (e.g., 3–4 minutes) and build as your endurance improves.
Final Thoughts:
These threshold sessions help improve speed, endurance and pacing for the Ironman run. Integrating them 1–2 times per week in a structured plan will help you hold race pace longer and finish strong.
Add these sessions to your weekly plan and turn strength and speed into your race-day weapon!
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 personalised advice.
