I trained in zone 2 for my half marathon, and it made me a faster runner

A half marathon is just a 5km warm-up, a 10k run, and a 5k recovery run, right? Yes, it’s that easy—especially when you tap into Zone 2 training.

With 6 full marathons and over 20 half marathons under my (running) belt, this is the first time I’ve actually slowed things down to speed things up—and I loved the training process.

Here’s how and why zone 2 training made me a faster, more efficient runner.

What is zone 2 training?

I’ll be honest. When I was asked to run the Royal Parks Half Marathon with Sweaty Betty, I was a little nervous. It had been seven years since my last race, and I wasn’t worried so much about the commitment to the training—but more about the hunger, burnout, and injuries that I’ve experienced when training for long distances.

So when I sat down with my coach, Kieran Driscoll, he suggested I do most of my training in zone 2. I was surprised. In the past, I’d always been about pushing my body to the limit—get the heart rate up, hit top speed, and log the miles as quickly as possible. Not this time, though!
“It’s not about going all-out,” Kieran told me. “It’s about working smarter.”

According to Kieran, Zone 2 training plays a critical role in building the aerobic base needed for sustained performance. It’s the foundation that helps your body endure for longer periods without fatiguing. Plus, it teaches your body to become more efficient at using fat as fuel, meaning you can run longer without hitting that dreaded wall.

In other words, you’re not just training for endurance; you’re teaching your body how to keep going without burning out too soon.

How does it feel to run in zone 2?

Like I’m cheating! It feels steady and comfortable—like I could run for hours (if boredom doesn’t get to me first). I even asked Kieran if I was doing something wrong. I wasn’t.

“Zone 2 training typically corresponds to a moderate intensity level where your heart rate is elevated, but you can still maintain a conversation without feeling notably breathless,” he explains. It makes sense.

I get a work call mid-run, and I can chat without gasping for air. I even drag my 11-year-old daughter out with me, knowing my pace will be slow and steady enough for us both to enjoy it.

Suddenly, training for a half marathon and running most days feels manageable. It feels less intimidating and less of a slog.

How do I work out my heart rate range for zone 2 training?

The specific heart rate range for Zone 2 training varies based on individual fitness levels, but it generally falls between 60% and 75% of your maximum heart rate. Luckily, my Garmin Lily 2 Active tracks it for me, buzzing whenever I drift out of range—something most of the best running watches and fitness trackers can do for you, too.

If you want to calculate it manually, here’s a quick and easy formula:

1. Subtract your age from 220 to estimate your maximum heart rate (MHR).
2. Multiply that number by 0.6 and 0.75 to get your Zone 2 range.

For example, if you’re 40 years old:

• 220 - 40 = 180 (MHR)
• 180 × 0.6 = 108 bpm
• 180 × 0.75 = 135 bpm

So, your Zone 2 heart rate range would be 108–135 bpm.

If you don’t have a watch or heart rate monitor, a good rule of thumb is the talk test—you should be able to hold a conversation without gasping for breath, but still feel like you're putting in some effort.

Why zone 2 makes great half marathon training

Zone 2 training is the foundation for developing the aerobic base that supports sustained effort over long periods. It improves the efficiency of your heart and lungs, making your cardiovascular system stronger and more capable of handling extended activity without excessive fatigue.

“Going slowly also lets your body use fat as fuel,” explains Kieran. “Training your body to do so helps improve stamina for long-distance events. It works by building slow-twitch muscle fibers (also known as type 1 muscle fibers), which have the highest mitochondrial density,” adds Kieran. “This makes them incredibly efficient at using fat for energy—an essential trait for endurance running and improving your overall running performance.”

The result? You'll be able to sustain your pace for longer periods of time and maintain a steady pace. Plus, Zone 2 running is great for recovery and reduces the risk of injury.

For half-marathon runners, this means better endurance, fewer energy crashes, and the ability to sustain a race pace without burning out too soon.

Final thoughts: is zone 2 training here to stay?

During previous training cycles, I’ve followed rigid running plans that involved hill sprints, speed intervals, and pushing through weekly miles without much thought to my heart rate. This time around, I’m taking a different path, quite literally. Most of my runs are now in Zone 2, with the occasional hill sprint thrown in when I feel like it. I’m currently training for the Landmarks Half Marathon, and surprisingly, I’m doing so with minimal stress or fatigue.

While I can't say it's all down to Zone 2, I do think it’s played a significant role in helping me manage the physical and mental challenges of training. I’m not as hungry after my long runs, and the pressure to hit ‘fast’ paces has been replaced by a focus on staying in Zone 2. That shift has made my running far more enjoyable, and it’s given me space to really dial in on my form—how’s my cadence? My foot placement? My arm swing? These little details are easy to overlook when you’re pushing the pace and just trying to tick off the miles as quickly as possible. So my biggest takeaway on zone 2 training has to be slowing down doesn’t mean falling behind.

"There’s certainly no shame in training at an easier pace," says Kieran. "It doesn’t make you any less of a runner. In fact, it makes you a smarter one. You’re training your body to go the distance without burning out, and you’re learning to pace yourself properly. This allows you to run strong and consistently all the way to the finish line. And that’s quite a feeling!"

Now, that’s a PB, (I mean, a feeling) worth chasing!