Marathon Training: What Is Zone 5 / VO2 Max?

MarathonZone 5 / VO2
Written By FLJUGA

SUMMARY:
Zone 5 sits around 93–100% of max heart rate with an RPE of 9–10. It represents VO2 max training. It feels intense, sharp and maximal. In marathon training, short sessions in this zone increase oxygen efficiency and develop the speed reserve that makes race pace feel more manageable. In this guide, we’ll explain what Zone 5 running is, how it boosts marathon performance and how to use it without risking burnout.

Black and white photo of elite marathon runners mid-stride during a race surrounded by cheering crowds.

Unlocking your speed ceiling

Zone 5 is not where marathoners live but it is where speed gets built. This is the intensity where your cardiovascular system works at full capacity. You cannot sustain it for long but training here lifts all other zones underneath. When you increase your VO2 max, you improve how easily you can run at lower intensities. For marathoners, that means cruising more efficiently and finishing with strength.

What is Zone 5 running?

Zone 5 is your VO2 max zone. The highest level of intensity in structured training. It is fast, hard and designed to challenge your upper limits.

Zone 5 Defined:

  • Heart Rate: 93–100% of max HR

  • Effort Level: 9–10 out of 10

  • Breathing: Heavy, unbroken effort

  • Pace: Faster than threshold pace, close to all-out

You will not hold this for long, but the gains can be lasting.

Why Zone 5 matters in marathon training

Marathon training is built on endurance but speed matters too. The ability to stay strong in the final miles or to surge through fatigue depends on your capacity at the top end. That is what Zone 5 builds.

Top Benefits of Zone 5 Running:

  • Increases VO2 Max
    Improves the maximum volume of oxygen your body can process

  • Boosts Anaerobic Power
    Enhances your ability to surge, respond and finish strong

  • Develops Neuromuscular Speed
    Trains fast-twitch fibers and running economy at high speeds

  • Sharpens Form Under Stress
    Improves running mechanics during high-intensity fatigue

  • Builds Mental Toughness
    Pushes you to stay focused under serious discomfort

Even though you will never race a marathon in Zone 5, the benefits filter down through every pace zone.

How to use Zone 5 in a marathon plan

You only need small amounts of Zone 5 to see big returns. These sessions should be used sparingly, with plenty of recovery and only after a solid aerobic base has been developed.

When to Use It:

  • During sharpening phases in the final 6 to 8 weeks

  • After building base in Zones 2 and 3

  • In short intervals with full recovery

When to Avoid It:

  • Early in a base-building cycle

  • When fatigued or injured

  • Without accurate pacing and control

Sample Zone 5 Workouts for Marathon Runners

Option 1: Short VO2 Max Repeats

  • 6 x 1 minute fast

  • 2 minutes Zone 1 between

  • Focus on form and controlled turnover

Option 2: Long Hill Repeats

  • 6 x 90 seconds uphill

  • Walk or slow jog back down

  • Power-based session to develop strength and speed

Option 3: VO2 Max Fartlek

  • 4 sets of: 2 minutes fast, 2 minutes easy

  • Zone 5 during effort, Zone 1 or 2 recovery

  • Controlled pacing with sharp effort and full recovery

Use no more than one Zone 5 workout per week. More is not better. Strategic timing is everything.

How do you know you are in Zone 5?

Zone 5 does not feel moderate. You will be working near your full capacity.

Key Indicators:

  • Heart Rate: 93–100% of max

  • Breathing: Hard, no conversation possible

  • Effort: 9 to 10 RPE

  • Pace: Faster than 5K pace

You should feel spent after each rep. This zone is designed to push your upper limit.

Common Mistakes with Zone 5 Training

Doing Too Much
Zone 5 training is intense. More volume does not mean more gains. It only leads to burnout.

Poor Recovery Between Intervals
Inadequate rest reduces the quality of each effort and increases injury risk.

Incorrect Pacing
Running too slow does not reach VO2 max. Running too fast sacrifices form and quality.

Adding Without Purpose
Zone 5 should only be added when specific performance goals require it.

Zone 5 vs Other Training Zones

Each zone serves a purpose in marathon training. Zone 5 is the highest gear. Use it to sharpen all other zones.

Use our free FLJUGA calculator to find your exact heart rate zones before you begin.

Why Zone 5 Works for Marathoners

It might seem counterintuitive, but training at very high intensity boosts your capacity at lower intensities. By raising your ceiling, you make marathon pace feel easier and more sustainable.

Why It Works:

  • Increases your aerobic power ceiling

  • Helps you run more efficiently at marathon pace

  • Gives you a finishing gear

  • Improves running economy and turnover

  • Adds variety and mental sharpness to training

Zone 5 is not about running longer. It is about running smarter.

FAQs: Zone 5 and Marathon Training

Can beginners use Zone 5?
Not at first. Focus on Zones 1 and 2. Add Zone 5 only after a strong aerobic base is built.

How often should I train in Zone 5?
Once per week at most. Quality matters more than quantity.

Do elites use Zone 5 for marathons?
Yes, especially in sharpening phases. Even though they race slower than VO2 max pace, they train to raise their aerobic ceiling.

Is it better than threshold training?
No. It is complementary. Use Zone 4 for sustainable intensity and Zone 5 for short, sharp stimulus.

FURTHER READING: EXPLORE THE FULL MARATHON ZONE SERIES

Training Sessions:

Final Thoughts: Use It to Lift Everything Else

Zone 5 isn’t where your marathon is raced, it’s what helps you finish fast, push through tough moments and lift your entire training ceiling. Use it sparingly. Pair it with a strong aerobic base and watch your performance sharpen as race day approaches.

These sessions aren’t about volume, they’re about precision. Just a few minutes at this intensity can drive major gains in speed, oxygen uptake and mental sharpness. When added at the right time, Zone 5 gives you the ability to surge, to respond and to hold form when the race starts to hurt. It’s not about going hard all the time. It’s about knowing when to go hard and making it count.

Ready to boost your VO2 max and finish your next marathon stronger?

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.

FLJUGA
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