The Basics of Zone 4 & Zone 5 Training for Hybrid Athletes

You can’t just grind your way to peak fitness.

If you’re doing every hard effort at the same intensity or skipping hard efforts entirely, you’re leaving performance on the table.

Whether your goal is to race Hyrox, set a PR in the 5K, or just become fitter in general, you need top-end training.

That means knowing how and when to tap into Zone 4 and Zone 5.

And if you're still figuring out where performance training fits into your identity, What is a Hybrid Athlete? breaks it all down, and shows why both strength and conditioning matter more than ever. 

Zone 4: Threshold Work ("Controlled Suffering”)

What it is:

Zone 4 is just below your max sustainable effort.

Roughly 30-60 minute race pace, or the hardest effort you could hold without completely crashing.

Feels like:

You’re working hard. Your breathing is deep and labored, but you’re not quite redlining. You could talk in short bursts, but you really don’t want to.

Purpose:

Zone 4 builds your lactate threshold: your ability to clear and tolerate lactate. That means you can go faster for longer without slowing down.

Real-world example:

-20 minute run at threshold

-3x6:00 at threshold pace with 1:00 standing rest

-5-6x1,000m at threshold with 1:00 standing rest

Why it matters for hybrids:

This is your engine-building zone.

Whether you're doing burpee broad jumps in a Hyrox race or a hilly 10K, Zone 4 increases the ceiling of your sustainable power.

Zone 5: VO₂ Max Training (Redline Efforts)

What it is:

Zone 5 is 93-100% of your max heart rate.

These are shorter, near-all-out efforts that you can only hold for a few minutes.

Feels like:

Heavy breathing, full focus. Talking is not happening. Your brain is saying “this better end soon.”

Purpose:

Zone 5 improves your VO₂ max, your body’s ability to use oxygen. A higher VO₂ max means more energy for both endurance and strength.

Real-world example:

-4x3:00 @ 5K pace with 2:00 easy between. 

-5-6x2:00 @ 5k pace with 1:00 easy between 

How to Use These Zones in Your Training

1. Don’t stack them back-to-back.

   They’re demanding. Give yourself 48+ hours between hard sessions.

2. Use Zone 4 for longer intervals or steady-state sessions.

   1-2x/week depending on your goals. Threshold runs, sustained bike efforts, or longer rowing intervals.

3. Use Zone 5 for shorter intervals.

   1x/week is plenty for most. And you don't need to be doing them year round. In fact, you really only need them for sharpening, roughly 4-8 weeks out from an event. 

4. Stick to the intended zone.

   Don’t let Zone 4 workouts drift into Zone 5. That defeats the purpose. And don’t hold back on Zone 5, go hard and recover.

5. Mix modalities.

   Run, bike, ski erg, especially if you want to reduce impact while pushing intensity.

It's very easy to screw up this type of training.

Many people go too hard on threshold work (and some not hard enough).

And many people go way too hard on sets 1 and 2 of a VO2max workout, and then output falls off a cliff the rest of the workout, completely missing the desired training effect.  

Call to Action

This week, pick one Zone 4 workout and/or one Zone 5 workout to add to your training.

If you’re unsure where to start, send me and email or a DM, and I’ll recommend a workout for you.

And if you want a fully customized training plan that balances strength, endurance, and recovery, without guessing or burning out check out my 1-on-1 coaching here.

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