Zone 2 Isn’t Dead. But It Might Be Overrated.

The Climb (#195)

Introduction

For the last few years, Zone 2 has been everywhere.

Podcasts.

YouTube.

Instagram.

Training plans.

And if you spend enough time in cycling circles, you could be forgiven for thinking that Zone 2 is the answer to almost everything.

Want better mitochondrial health?

Zone 2.

Want to burn more fat?

Zone 2.

Want better endurance?

Zone 2.

Want to live longer?

More Zone 2.

But some recent research has challenged the idea that Zone 2 is somehow uniquely better than other forms of training.

And I think that’s a really useful conversation to have.

Because I’m not about to tell my clients to stop doing Zone 2.

Far from it.

But I also don’t think cyclists over 40 should spend all their available training time riding easy and assume that is automatically the best route to improving fitness.

The answer, as usual, is somewhere in the middle.

What The Research Actually Says

A 2025 review published in Sports Medicine looked at the claim that Zone 2 is the optimal intensity for increasing mitochondrial capacity and fat oxidation.

The conclusion?

The evidence does not support Zone 2 as being uniquely superior for those adaptations.

The authors found that higher-intensity exercise can also drive strong mitochondrial and cardiometabolic adaptations, and argued that higher intensities may be especially important for people who have limited time to train.

That matters for the cyclists I coach.

Because most of them are not professional riders doing 20 hours per week.

They have jobs.

Families.

Travel.

Stress.

Maybe 4–8 hours a week to train.

So if you only have limited training time, spending every session at low intensity probably is not the best use of that time.

That does not make Zone 2 useless.

It simply means it should not be treated like a magic bullet.

Why Zone 2 Became So Popular

The logic behind Zone 2 makes sense.

Professional endurance athletes spend a huge amount of time at lower intensities.

They also have exceptional mitochondrial density, aerobic fitness and metabolic health.

So the assumption became:

“They do loads of Zone 2, therefore Zone 2 must be the thing creating those adaptations.”

But there is a problem with that logic.

Professional cyclists spend huge amounts of time at low intensity because they have to.

If you are training 15, 20 or even 25 hours per week, you cannot do all of it hard.

You would be exhausted very quickly.

So large amounts of easy riding allow them to accumulate volume while still recovering enough to perform their harder sessions.

That is very different from the average cyclist who has only four or five hours available.

This is why context matters.

So Should You Just Do Intervals Instead?

Not quite.

High-intensity training is extremely effective.

And the research supports it.

Studies in older adults have shown that interval-based training can improve cardiorespiratory fitness and cardiometabolic markers, and some studies have found advantages over moderate continuous exercise for certain outcomes.

That is particularly relevant for cyclists over 40.

You absolutely can still improve VO2 max, power and cardiovascular fitness as you get older.

But here is the part that gets lost when people start arguing about whether Zone 2 or HIIT is “better.”

You cannot do high-intensity training all the time.

At least not productively.

If every ride becomes an interval session, eventually your legs feel flat, motivation drops, recovery suffers and performance starts going backwards.

That is exactly what I try to avoid with clients.

My Coaching Philosophy: Make The Hard Work Count

This is how I think about training.

If you are going to ride hard, I want that session to count.

I want you fresh enough to hit the numbers.

I want the session to create the stimulus we intended.

And I want you recovered enough afterwards to adapt to it.

What I do not want is five or six rides a week that all feel “a bit hard.”

That is where cyclists get stuck.

They turn their Zone 2 ride into Zone 3.

They chase people up climbs.

They smash the group ride.

They do intervals the next morning.

Then they wonder why their FTP has plateaued.

You are not short of training stress.

You are short of recovery.

The Problem With The Grey Zone

This is probably the biggest thing I see with cyclists over 40.

They do not train too easy.

They train too moderately hard, too often.

Every ride sits somewhere in the middle.

Hard enough to create fatigue.

Not hard enough to create a really clear high-intensity stimulus.

That makes recovery harder and often means the sessions that matter most are done on tired legs.

I would much rather see someone do:

One genuinely good interval session.

One or two genuinely easy Zone 2 rides.

One longer endurance ride.

And perhaps some strength work.

Than spend the whole week riding at an intensity that leaves them permanently tired.

Where Zone 2 Still Fits

Zone 2 is still incredibly useful.

It builds aerobic volume.

It helps develop endurance.

It allows you to train without accumulating huge amounts of fatigue.

It is useful for longer rides.

It gives you space to recover between hard sessions.

And for people who enjoy riding socially or spending time outside, it is also sustainable.

That last point matters more than people think.

The best training plan is not the one that looks perfect in a study.

It is the one you can actually stick to.

If every session is brutal, people eventually stop enjoying the bike.

And when motivation goes, consistency usually follows.

Why Intervals Matter More When Time Is Limited

This is where higher-intensity work becomes especially useful.

If you only have a few hours per week, intervals give you a lot of return for your time.

You can create a strong cardiovascular stimulus in 30–60 minutes.

That makes them ideal for busy cyclists.

This is exactly why I often programme one key interval session each week.

Sometimes two, depending on the rider, the phase of training, and the rest of their life.

But those sessions need to be protected.

If you are already tired from three days of moderately hard riding, the interval session becomes much less effective.

So once again, the easier work has a job.

It helps you arrive fresh enough to make the harder work count.

What About Age?

One of the more interesting parts of the discussion in the transcript was research around ageing and mitochondrial function.

A 2025 study looking at physically active men across the adult lifespan found that habitual physical activity was associated with preserved mitochondrial energetics and function, although some age-related changes in calcium handling still occurred.

The practical takeaway is simple.

Keep exercising.

Keep challenging the cardiovascular system.

Keep moving.

You do not need to accept that your fitness must collapse simply because you are getting older.

But you do need to train intelligently.

The Balance I Use With Clients

For most cyclists over 40, I like a simple balance.

One key interval session.

One or two easy Zone 2 or endurance rides.

One longer ride.

One or two strength sessions.

Then adjust around work, sleep, stress and recovery.

Some riders can tolerate more intensity.

Some need less.

Some have 10 hours per week.

Some have four.

The structure changes.

The principle does not.

Easy enough to recover.

Hard enough to adapt.

That is the balance.

How To Know If You’re Doing Too Much Intensity

There are some obvious signs.

Your legs constantly feel heavy.

Your interval numbers are dropping.

Your resting heart rate is higher than normal.

You are sleeping poorly.

You feel irritable.

You are losing motivation.

Your “easy” rides feel harder than they should.

You start needing more caffeine just to train.

That is not a sign that you need another interval session.

It is usually a sign that the training load is too high for your current recovery capacity.

How To Know If You’re Doing Too Much Easy Riding

The opposite can happen too.

If all you ever do is Zone 2, you may build a good aerobic base, but eventually you need a stronger stimulus if you want to keep improving performance.

That is especially true if your training time is limited.

If your FTP has not moved for months and every ride is steady, the answer may not be more steady riding.

It may be adding one properly structured high-intensity session.

A Simple Week You Could Try

If you train around 5–7 hours per week, something like this can work well:

Monday: Rest or strength.

Tuesday: Interval session.

Wednesday: Easy Zone 2.

Thursday: Strength or recovery.

Friday: Rest.

Saturday: Longer endurance ride.

Sunday: Easy ride or optional recovery.

That is not complicated.

And that is the point.

You do not need an exotic training system.

You need enough intensity to drive adaptation and enough easy riding to allow you to recover from it.

Action Steps

Look at your last two weeks of training.

Count how many rides were genuinely easy.

Count how many were genuinely hard.

Then ask whether too many sessions sat somewhere in the middle.

If you are training 4–6 hours per week, make sure you have at least one properly structured interval session.

If you are training more volume, protect your easier days so that the hard sessions stay high quality.

And if you constantly feel tired, reduce intensity before you add more.

The goal is not to prove how much training you can survive.

The goal is to create the right amount of stress for your body to adapt to.

Final Thought

Zone 2 is not dead.

And interval training is not the answer to everything either.

The problem starts when cyclists treat either one as the only thing they need.

Zone 2 helps you accumulate volume, build endurance and recover.

Intervals give you a powerful stimulus and are incredibly efficient when time is limited.

You need both.

And for cyclists over 40, the balance becomes even more important.

Because the healthier you are off the bike, the more consistently you can train on it.

So stop asking:

“Should I do Zone 2 or intervals?”

Start asking:

“What balance of easy and hard training can I recover from and repeat consistently?”

That is where the real progress happens.

Whenever you're ready, here are the ways I can help you:

1. The Cycle Lean Coaching: Personalised 1:1 Coaching for Cyclists Who Want to Drop 6–12 kg and Add Up To 60 Watts of FTP While Riding 6-8 hours a Week!
2. The Cycle Lean Blueprint: The science-backed 12-week blueprint to cycle leaner, climb stronger, and become the most resilient version of yourself.