Triathlon Training: What Is Zone 4 / Threshold Training?
SUMMARY:
Zone 4 — around 87–93% of max heart rate, 91–105% of FTP, and 99–104% of CSS swim speed (RPE 7–8) — is the threshold zone that pushes your aerobic limit across all triathlon disciplines. It feels hard but controlled, sitting just below your redline. Training in Zone 4 improves lactate tolerance, fatigue resistance, and your ability to hold race effort under pressure — especially in the final stages of hard sessions or competition.
What is Threshold Training?
Triathlon training isn’t just about going long and slow or sprinting at top speed — it’s about mastering the in-between efforts, too. That’s where threshold training comes in. Threshold training is the sweet spot between aerobic endurance and all-out effort.
It’s where the body learns to sustain high-intensity work without fading, helping triathletes push harder, race stronger and delay fatigue. Training at this level boosts speed, builds endurance, and improves overall race performance.
Whether training for a sprint triathlon or an Ironman, threshold sessions are a game-changer for taking fitness to the next level.
Threshold training focuses on working just below or at lactate threshold—the intensity where the body starts producing more lactate than it can clear. At this effort, breathing is deep but controlled, muscles are working hard, and sustaining the pace feels challenging but doable.It’s the point where the body learns to handle higher intensities without burning out.
Triathlon Zone 4 / Threshold Guidelines
Zone 4 is where performance gains start to sharpen. This is the effort level where you train just below your redline — building stamina, control, and high-end endurance without tipping into burnout.
Heart Rate: 87–93% of Max HR
Bike Power: 91–105% of FTP
Swim Pace: 99–104% of CSS
RPE (Perceived Effort): 7–8 out of 10
Effort: Hard but sustainable
Use FLJUGA’s free calculators to find your exact training zones.
Why Threshold Training is Important for Triathletes
Builds Race-Day Speed and Stamina
Threshold training allows triathletes to hold a faster pace for longer without feeling drained. This means stronger bike splits, faster run legs, and better overall race times.
Delays Fatigue
By increasing the body’s ability to process and clear lactate efficiently, threshold training helps athletes push harder without hitting the wall too soon.
Improves Pacing and Control
Triathletes who train at threshold effort develop a better sense of race pacing, making it easier to stay in control and avoid early burnout.
Increases Aerobic Power
Threshold sessions strengthen the heart, lungs, and muscles, improving overall endurance and making race pace feel easier over time.
How to Incorporate Threshold Training into a Triathlon Plan
Cycling Threshold Workout Example
Warm-up: 15 minutes easy spinning
Main Set:
• 3 x 10 minutes @ Zone 4
• 5-minute easy spin recovery between efforts
Cooldown: 10 minutes easy spinning
Running Threshold Workout Example
Warm-up: 10-15 minutes easy jogging
Main Set:
• 4 x 8 minutes @ Zone 4
• 3-minute jog recovery between efforts
Cooldown: 10 minutes easy running
Swimming Threshold Workout Example
Warm-up: 400m easy swim + drills
Main Set:
• 5 x 200m @ Zone 4
• 30 seconds rest between reps
Cooldown: 200m easy swim
When to Use Threshold Training
Zone 4 training is most effective when your body is primed to absorb the intensity.
Ideal moments to include threshold work:
During the build phase of a triathlon plan
After establishing a strong aerobic base
When training for Olympic, 70.3, or Ironman races
On days when you’re rested, fueled, and focused
To sharpen pacing and endurance close to race day
Aim for 1–2 sessions per week depending on your experience and phase of training.
When to Avoid Threshold Training
Threshold work is powerful, but timing matters.
Avoid Zone 4 efforts if:
You’re recovering from illness or injury
You’re feeling sleep-deprived, fatigued, or run down
You’re early in a base-building block
You’ve done a recent high-intensity session or race
You’re struggling with motivation or form — pushing hard won’t fix it
Threshold training works best when it’s purposeful, not forced. Prioritise quality over quantity to avoid burnout.
Mini FAQ: Threshold Training in Triathlon
What is threshold training in triathlon?
Threshold training focuses on working just below or at lactate threshold—the intensity where the body starts producing more lactate than it can clear.
Why is threshold training important for triathletes?
It builds your ability to hold a strong pace without burning out, especially critical for sustained efforts on the bike and run.
How often should triathletes do threshold workouts?
Most triathletes benefit from one threshold session per week, ideally after building a strong aerobic base.
What do threshold workouts look like?
Common sessions include intervals like 3 x 10 minutes at threshold pace with short recoveries, or longer efforts at around 87–93% of max heart rate (run), 91–105% of FTP (bike), and 99–104% of CSS swim speed (RPE 7–8). Check your heart rate and FTP zones with FLJUGA’s free calculators. Start here.
When should I include threshold training in my plan?
Include threshold work during the build phase of your training to boost race-specific endurance and improve pacing control.
Final Thoughts
Threshold training is a key ingredient in triathlon success, bridging the gap between endurance and speed. By consistently training at this effort level, triathletes can race harder, last longer, and perform stronger when it matters most.Adding threshold workouts to a training plan helps increase sustainable speed, improve pacing, and build resilience against fatigue, making race day feel smoother and more controlled.
Are you ready to dial into your sweet spot and unlock new endurance with threshold training?
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.
