Push Your Limits: Zone 5 Training for Ironman 70.3!
Want an Edge When Everyone Else is Holding Back?
Most athletes training for an Ironman 70.3 focus on building aerobic endurance—and they should.
But if you want to surge past the pack, power over hills, and finish strong? You need Zone 5.
What Is Zone 5 Training?
Zone 5 is the anaerobic zone—where intensity is sky-high, and efforts are short, sharp, and unsustainable for long durations. It’s where your body maxes out its oxygen use and generates high lactate levels.
Zone 5 Training Metrics:
Heart Rate: ~90–100% of Max HR
Cycling Power: 106–120% of FTP
Running Pace: 3K–5K pace or faster
Effort Level: 9–10/10 (very hard to maximal)
Duration: 30 seconds to 3 minutes per interval
Primary Energy System: Anaerobic with some aerobic contribution
This zone demands a lot—but it gives back even more when used right.
Why Use Zone 5 in Ironman 70.3 Training?
1. Increases VO2 Max
Zone 5 pushes your cardiovascular system to its max, improving your body’s ability to deliver and utilise oxygen. That means you can go faster at lower perceived effort.
2. Boosts Speed and Power Output
High-intensity intervals improve neuromuscular coordination and explosive strength, making your bike and run more efficient and powerful.
3. Enhances Lactate Tolerance
Training at this level teaches your body to tolerate and buffer high lactate loads, which helps delay fatigue during tough segments or surges on race day.
4. Prepares You for Race-Day Surges
Climbing, passing, pushing to the finish—you need gear changes, even in an endurance race. Zone 5 trains your body to respond when it matters most.
How to Use Zone 5 Training in Your 70.3 Prep
Zone 5 is powerful, but it’s also demanding. Use it strategically, not excessively.
Here’s how:
1. Limit to 1–2 Sessions Per Week
Too much Zone 5 can lead to burnout. Schedule 1–2 high-intensity sessions per week during key phases.
2. Time It Right in the Season
Base Phase (Early): Focus on aerobic zones. Save Zone 5 for later.
Build Phase (Mid): Introduce 1–2 Zone 5 sessions weekly to sharpen speed.
Peak Phase (4–6 Weeks Out): Reduce volume but keep intensity for race sharpness.
Taper (Final 1–2 Weeks): Avoid excessive Zone 5; shift to race pace and recovery.
3. Combine with Endurance Work
Insert short bursts of Zone 5 within longer endurance workouts to mimic race fatigue and improve aerobic/anaerobic crossover.
4. Prioritize Recovery
Zone 5 creates deep fatigue. Allow ample recovery (Zone 1–2 or rest) between efforts and sessions to adapt without overreaching.
Zone 5 Workout Examples for Ironman 70.3
Cycling Workouts
VO2 Max Intervals: 4–6 x 2–3 minutes @ 110–120% FTP, 2–3 min recovery
Hill Repeats: 6–8 x 30–60s uphill @ max effort, 2–3 min spin down
Tabata Intervals: 8–10 x 20s all-out / 10s rest (advanced)
Running Workouts
Hill Sprints: 8–12 x 30s hard uphill, walk or jog down
400m Repeats: 6–10 x 400m @ 5K pace or faster, equal time recovery
Fartlek Sets: 5 x 2 min hard / 3 min easy jog
Swim Workouts
Sprint Sets: 10–15 x 50m all-out, 30s rest
Threshold Repeats: 6–8 x 100m hard, 1:1 work:rest
Broken 400s: 4 x 100m with 15s rest between reps
When to Skip Zone 5
Don’t force Zone 5 work if:
You’re already carrying fatigue
Your aerobic base isn’t established yet
You’re in the final taper
Your technique breaks down under intensity
Remember: Zone 5 is the icing—not the cake.
Mini FAQ
Q: Is Zone 5 training necessary for Ironman 70.3?
A: It’s not essential, but it’s highly effective when used strategically. It boosts speed, VO2 max, and race-day strength.
Q: When should I start adding Zone 5?
A: Introduce it during the build phase, about 12–6 weeks before race day. Limit to 1–2 sessions per week.
Q: Can Zone 5 training make me faster at race pace?
A: Yes—by raising your VO2 max and improving lactate clearance, it allows you to go faster with less effort at your race pace.
Final Thoughts: High Effort, High Return
Zone 5 training pushes your boundaries—and builds the kind of speed, power, and resilience that sticks when racing gets hard.
Use it to sharpen. Use it to surge. Use it to break through. But above all—use it smart.
Ready to unlock your speed and power? Zone 5 is where races are won…one brutal interval at a time.
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.