Zone 2 Training: Why Slowing Down Could Help You Get Fitter, Faster and Healthier

You don't always have to train harder to get fitter. In fact, sometimes the smartest thing you can do is slow down.

If you've spent any time reading any fitness content recently, you'll probably have heard the term Zone 2.

Zone 2 training has become something of a fitness buzzword, with claims that it is the secret to better endurance, improved fat burning, healthier mitochondria and even longevity.

But what actually is Zone 2? and is it really the magic bullet that social media sometimes makes it out to be?

So, what exactly is Zone 2?

Heart rate training divides exercise intensity into different zones, usually from Zone 1 through to Zone 5. Broadly:

• Zone 1: very easy/recovery

• Zone 2: easy aerobic work

• Zone 3: moderate/challenging aerobic work

• Zone 4: hard/threshold work

• Zone 5: very hard/maximal efforts

Zone 2 is generally considered a low-to-moderate intensity aerobic effort, where your body can produce most of its energy aerobically.

For runners, cyclists or any form of aerobic exercise this usually means an effort that feels relatively comfortable and controlled. The simplest way to judge it?

• You should be able to talk: Not necessarily deliver a speech without pausing, but you should be able to hold a conversation without gasping between every sentence.

• Zone 2 can feel ridiculously slow: You may even find yourself thinking: "Surely this can't be doing anything?" But it is.

Why is Zone 2 useful?

One of the biggest benefits of Zone 2 training is that it allows you to accumulate a decent amount of aerobic work without creating huge amounts of fatigue.

That's incredibly useful.

When you're running, cycling, rowing or using another cardiovascular modality at a lower intensity, you're training your aerobic energy system while putting less stress on your body than you would during repeated hard sessions.

Over time, this can contribute to improvements in cardiovascular fitness and your ability to sustain exercise for longer.

For endurance athletes, that's obviously important.

But it's also important for everyday health.

We don't all need to be training for a marathon to benefit from improving our aerobic fitness.

But here's where things get interesting...

There's a lot of discussion around Zone 2 improving mitochondrial function and your body's ability to use fat as a fuel source.

And there is good physiological reasoning behind why aerobic training can improve our ability to produce energy and sustain exercise.

However, the current evidence doesn't support the idea that Zone 2 is uniquely superior to higher-intensity exercise for improving mitochondrial health.

A 2025 review published in Sports Medicine specifically challenged the increasingly popular claim that Zone 2 is the optimal exercise intensity for improving mitochondrial and fat-oxidation capacity.

The researchers concluded that the evidence doesn't support Zone 2 as the optimal intensity, and that higher-intensity exercise can be particularly important for improving cardiorespiratory fitness and cardio-metabolic health – especially when people have limited time to exercise.

So, no...

You don't need to spend hours in Zone 2 to "fix" your mitochondria.

And you definitely shouldn't think that a Zone 2 walk or jog means you can forget about doing anything harder.

Zone 2 isn't about training exclusively at Zone 2

This is probably the most important point I want you to take away.

Zone 2 is one tool in the toolbox. Not the whole toolbox.

• If you're training for a marathon, half marathon, Hyrox, cycling event or simply trying to improve your fitness, your body benefits from exposure to different intensities.

• Easy training helps you build your aerobic base and accumulate volume.

• Harder training challenges your cardiovascular system in a different way and can improve things such as VO₂ max and high-end aerobic performance.

• Strength training provides another stimulus entirely.

• And recovery allows your body to actually adapt to all of the above.

Think variety rather than "one perfect zone".

Research into endurance training supports this idea.

A 2024 systematic review and meta-analysis found that a polarised approach, combining substantial low-intensity training with some high-intensity work, can be particularly effective for improving VO₂ peak, although the advantages aren't universal across every measure of endurance performance.

In one recent systematic review, approximately 75–80% low-intensity training combined with around 15–20% higher-intensity training appeared effective for improving VO₂ max and exercise economy in endurance athletes.

That doesn't mean everyone needs to obsess over hitting exactly 80/20.

Training needs to be individualised.

But it does reinforce the idea that most training shouldn't be hard – while some training probably should be.

Runners often get Zone 2 wrong?

I see this all the time. Someone decides they're going to "run easy"...then they head out the door and run every mile a little bit faster than they should.

They're not running hard enough to get the full benefits of a quality speed session.

But they're not running easily enough to make it a genuinely easy aerobic run either.

They end up living in the grey zone.....Every run becomes moderately hard.

And that can make it difficult to recover properly before the next session.

Instead, imagine your week looking more like this:

• Easy days = genuinely easy.

• Hard days = deliberately hard.

• Recovery days = actually recover.

That's a much more sensible approach to training.

But what about weight loss?

Another reason Zone 2 has become so popular is because of the idea that it is the "fat-burning zone".

This needs a little clarification.

• Yes, at lower exercise intensities, a greater proportion of the energy you use can come from fat oxidation but that doesn't mean Zone 2 = automatic fat loss.

Fat loss ultimately depends on overall energy balance over time.

Your body doesn't suddenly switch into a special "fat-burning mode" at a particular heart rate.

For someone trying to lose body fat, Zone 2 can be incredibly useful because it allows you to increase physical activity without necessarily generating the same level of fatigue as repeated high-intensity sessions.

But it works best alongside:

• resistance training

• sufficient protein

• a nutritious, sustainable diet

• adequate sleep

• daily movement

• and appropriate higher-intensity exercise where suitable

There is no magic heart-rate zone that overrides the basics.

This matters even more as we get older

For my 40+ clients, I don't want every training session to feel like a battle.

There is enormous value in being able to train consistently.

Consistency is much easier when your programme includes different levels of intensity rather than asking you to go hard every time you exercise.

As we get older, maintaining cardiovascular fitness, muscle mass, strength, power, balance and mobility all become important parts of healthy ageing.

That's why I don't believe in choosing between cardio OR strength or Zone 2 OR HIIT or running OR lifting weights. We need a combination.

The current physical activity guidelines recommend adults accumulate 150–300 minutes of moderate-intensity aerobic activity per week, or 75–150 minutes of vigorous activity, alongside muscle-strengthening work on at least two days per week.

How can you actually use Zone 2?

You don't need to overcomplicate it.

For runners, Zone 2 is particularly useful for:

• Easy runs: These should feel comfortable rather than competitive.

• Long runs: Especially during marathon and endurance training, where the aim is to build your ability to keep moving for a prolonged period.

• Recovery runs: If you've completed a hard session, an easy aerobic run can help you keep moving without adding another big training stress.

• Cross-training: Cycling, rowing, swimming, incline walking and other cardiovascular activities can all provide an aerobic stimulus.

• Don't underestimate walking: A brisk walk can be a fantastic way of accumulating aerobic activity, particularly if you're new to exercise, returning from injury or simply having a lower-energy day.

Do you have to use a heart-rate monitor?

No. This is another area where I think we can overcomplicate things.

Heart rate can be useful, particularly if you're training for an endurance event, but it's not essential.

Your heart rate can be affected by:

• heat

• dehydration

• caffeine

• stress

• poor sleep

• illness

• hormones

• hills

• accumulated fatigue

So don't panic if your Garmin tells you you're suddenly in Zone 3 when you feel perfectly comfortable.

Use the numbers as information, not instructions from the fitness gods.

The talk test and perceived exertion are still incredibly useful tools.

So, should I be doing more Zone 2?

Probably.

But not necessarily because Zone 2 is some magical training intensity.

You should probably be doing more easy aerobic exercise because it is an effective, sustainable way to improve your fitness, accumulate training volume and build your aerobic base without constantly beating yourself up.

But I'd encourage you to think bigger than Zone 2.

Build your fitness from multiple directions.

• Easy aerobic work to build endurance.

• Higher-intensity work to challenge your cardiovascular system.

• Strength training to maintain and build muscle, strength and resilience.

• Mobility and movement to keep you moving well.

• Recovery so your body can adapt.

• And plenty of everyday movement outside your formal workouts.

The goal isn't to train harder. It's to train smarter.

• Sometimes that means pushing yourself.

• And sometimes the smartest thing you can do is slow down.

• So next time you're out for an easy run and you're tempted to speed up because everyone else seems to be overtaking you...Let them go.

Your ego might not thank you. But your training plan probably will.

Want help working out how to use Zone 2 in your own training?

If you're training for a marathon, improving your fitness, returning to running or simply want to become stronger and fitter as you get older, your training shouldn't be based on doing the same thing every session.

It's about getting the right balance of intensity, strength, recovery and progression for YOU.

If you'd like help putting that together, get in touch.

Train smart. Get stronger. Stay active for life.