Triathlon Run Training: What Is Zone 4 / Threshold?
SUMMARY:
Zone 4 — around 87–93% of max heart rate (RPE 7–8) — is the threshold zone for triathlon run training. It feels hard but controlled, demanding focus and rhythm to sustain. Training in this zone improves lactate tolerance, running efficiency, and your ability to maintain race effort under fatigue — especially critical for strong finishes and run segments off the bike.
What Is Zone 4 / Threshold Running?
Zone 4 running — often referred to as threshold training — is the effort right at your lactate threshold. It’s hard, steady, and sustainable. In this zone, your body adapts to faster speeds without breaking down, helping you run faster for longer.
Zone 4 / Threshold Running Characteristics:
Heart rate: 87–93% of max (Try FLJUGA’s free calculator to find your zones)
Effort level (RPE): 7–8
Breathing: Deep, controlled
Sustainable duration: 20–40 minutes of work
Training in Zone 4 helps you build pace endurance — the ability to hold your target race pace without fading.
Why Zone 4 / Threshold Running Matters
Improves Sustainable Race Pace
Zone 4 running trains your body to maintain a strong pace without blowing up. It helps bridge the gap between comfortable training and real race-day intensity.
Delays Fatigue
Threshold workouts improve your body’s ability to manage lactate buildup, allowing you to push harder, longer.
Sharpens Pacing and Control
Training at this intensity teaches you what a hard but manageable pace feels like, so you can dial in your race effort without overdoing it.
Builds Endurance Under Stress
These sessions strengthen your heart, lungs, and running muscles — all while simulating race-level effort.
How to Know You're in Zone 4 / Threshold Running Effort
You're likely in Zone 4 when:
Your breathing is heavy but under control
You can speak short phrases, but not full sentences
You feel like you're working near your limit, but can maintain the effort
Your heart rate is between 87–93% of your max
(Try FLJUGA’s free heart rate calculator to check your zones accurately)
Sample Zone 4 / Threshold Running Workout
Warm-up:
15 minutes easy jog + 4 × 20-second strides
Main Set:
4 × 8 minutes at Zone 4 / threshold effort
Jog 3 minutes between each
Cooldown:
10 minutes easy running
This threshold session teaches your body how to stay efficient under pressure — the exact intensity you'll rely on in your next race. Want more structured workouts? Explore these
When to Use Zone 4 / Threshold Running in Your Plan
Zone 4 / threshold workouts should come after building a solid aerobic base (mainly in Zone 2). Once per week is typically enough during your build phase.
To progress your threshold training:
Increase interval duration
Add more reps
Reduce recovery time
Pair with steady Zone 2 running for contrast
Zone 4 / Threshold Running Compared to Other Training Zones
Here’s how Zone 4 fits within the broader training zone model:
Zone 1 (Active Recovery): Very easy effort, used for recovery runs and cooldowns
Zone 2 (Endurance): Easy aerobic running for base building
Zone 3 (Tempo): Moderate effort, used for steady-state runs
Zone 4 (Threshold): Hard but sustainable, race-specific pace development
Zone 5 (VO2 Max): Very hard, short-duration intervals to boost peak performance
Zone 4 sits at the edge of control — it’s not a sprint, but it’s not easy. It’s where you prepare to race, not just train.
Zone 4 / Threshold Running for Different Distances
While the effort stays the same, how you use Zone 4 depends on the distance you're training for. Here’s how threshold training supports different race goals:
5K:
Improves your ability to sustain speed without fading. Zone 4 helps sharpen your control at high intensities and builds confidence in the final kilometre.
10K:
Zone 4 closely matches your race pace in this distance. Training here improves efficiency, pacing, and tolerance to discomfort.
Half Marathon:
Threshold workouts increase the pace you can hold over long periods — especially useful in the middle to late stages of a half marathon.
Marathon:
While marathon pace is slower (often Zone 3), Zone 4 sessions expand your aerobic ceiling, help with surge control and improve strength for hill sections and final pushes.
Mini FAQ: Zone 4 / Threshold Running Explained
What is Zone 4/ Threshold Running?
It’s a threshold-level effort — hard but sustainable — that builds endurance and speed together.
Is Zone 4 the same as threshold?
Yes. Most modern training systems equate Zone 4 with threshold intensity (LT2).
How often should I do Zone 4 workouts?
One session per week during race build-up is ideal to see strong results.
What pace is Zone 4 for me?
It’s the pace you can hold for around 40–60 minutes. Use FLJUGA’s heart rate or lactate threshold calculator to set it precisely.
Can beginners do Zone 4/ Threshold?
Yes — but only after building a strong base in Zone 2. Start with shorter reps like 4–6 minutes and build up from there.
Final Thoughts: Why Zone 4 / Threshold Running Works
Threshold training — or Zone 4 running — is one of the most effective ways to improve your race fitness. It helps you hold faster paces, delay fatigue, and stay mentally in control. It’s not glamorous, but it’s powerful. If you’re ready to level up your training and take ownership of your pace, make Zone 4 a consistent part of your weekly schedule. Just one session a week can change how you race — and how you recover.
Is Zone 4 the edge your run training needs?
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.
