What Is Zone 2 Cardio, and Do You Actually Need It?

You've probably heard "Zone 2" thrown around and quietly had no idea what it meant. Here's the plain-English answer and whether you actually need to think about it.

Zone 2 is just a name for a sustained, conversational pace: the effort level where you could talk without gasping, hold for 30-60 minutes, and finish feeling like you could do more. It's the specific intensity that builds your aerobic engine most efficiently, and for most women who aren't training for athletic performance, the easiest way to get it isn't a treadmill program. It's walking more than you currently are.

One of my long-term clients came to me recently with a specific anxiety: she'd heard Zone 2 was important for heart health and had no idea if she was getting it or what she should be doing. She already does strength training and Pilates consistently. She's active. She just didn't know if it was enough.

We didn't add a cardio program. We looked at where she was already moving and found the gaps. She was Ubering to the train station and back. We switched that to a 15-minute walk each way. On her rest day, instead of staying home, she started walking to see family: 30 to 60 minutes, easy pace. That was it. Problem solved, anxiety resolved, no treadmill required.

That's Zone 2 in practice for most women. Not a program: a practice.

What the five heart rate zones actually are

Think of your heart as having five gears:

• Zone 1: Easy recovery: light movement, very low effort
• Zone 2: Steady highway speed: you could hold a full conversation, sustainable for an hour or more
• Zone 3: Picking up pace: you're working, breathing harder, short sentences only
• Zone 4: Hard intervals: one-word answers, max
• Zone 5: All-out sprint: can't talk at all

A warm-up typically moves you from Zone 1 into Zone 2 as your heart rate rises — Zone 1 is where you start, not where you stay.

What the research actually says about Zone 2, and where it gets complicated

Zone 2 has been positioned in popular media as the optimal intensity for building mitochondria, burning fat efficiently, and supporting long-term cardiovascular health. That case was built primarily by Dr. Iñigo San-Millán, an exercise physiologist at the University of Colorado who spent decades testing elite endurance athletes including Tour de France winners and found that Zone 2 was where they saw the biggest improvements in mitochondrial function and fat oxidation.

The context: elite endurance athletes train 20-30 hours a week. Extrapolating from their training to a general population recommendation is a significant leap, and a June 2025 narrative review published in Sports Medicine makes exactly that challenge.

The review challenges the broad endorsement of Zone 2 training for members of the general public, arguing it contradicts substantial evidence supporting high-intensity exercise for improving mitochondrial capacity and cardiometabolic health. Much of the research cited in support of Zone 2 actually studied moderate intensity continuous training at intensities above Zone 2, meaning the Zone 2 label was being applied to findings that don't strictly support it.

The honest takeaway for someone training a few hours a week: consistent moderate movement matters, and some higher intensity work may be more efficient for cardiovascular and mitochondrial benefits than true Zone 2 specifically. If you're sedentary, any movement helps significantly. If you're already active, the Zone 2 versus higher intensity distinction matters less than showing up consistently.

This is an area where the science is actively evolving and genuinely contested, and I'll share more about where I personally land on it below. What I can tell you is what I actually recommended to my client, and why it worked.

How to know if you're actually in Zone 2

The simplest check is the talk test. Zone 2 is the pace where you could actually have a real conversation: share what's going on, tell a story, chat without gasping. The moment talking becomes effortful, you've drifted into Zone 3.

The most common mistake isn't picking the wrong zone on purpose; it's drifting higher without noticing. True Zone 2 feels almost suspiciously easy. If it doesn't feel a little boring, you're probably not in it.

For a more precise number, there's a formula called the Karvonen method that factors in both your age and your resting heart rate to give you a personalized Zone 2 heart rate range, more accurate than the standard 220-minus-your-age estimate. Most wearables (Garmin, Apple Watch, Oura) can calculate this automatically, worth using if you're a data person, not necessary if you're not.

A note on where this sits in my own practice

Full disclosure: I spent years doing exclusively cardio, stairmaster, treadmill, elliptical, hours on machines, before I discovered strength training in my late twenties and haven't looked back. Cardio isn't where my coaching expertise lives. I prioritize strength training, 6-8K steps a day, and recovery. I probably drift into Zone 3 myself when I do cardio.

But Zone 2 is a question I get consistently from clients, and I wanted to give you the clearest answer I could, grounded in the research that actually exists on it, not personal experience I don't have. Dr. San-Millán's work in particular is worth going deeper on if this topic interests you.

How much Zone 2 do you actually need

The American Heart Association recommends at least 150 minutes a week of moderate-intensity activity: a conversational pace, roughly Zone 2. That's five 30-minute sessions, three 50-minute sessions, or a 15-minute walk to the train station twice a day on most days.

Worth noting: the AHA's full guidance isn't just cardio. It also includes at least two days a week of muscle-strengthening activity, spending less time sitting, and the observation that even light-intensity movement offsets some of the risks of being sedentary. That's a framework that maps almost exactly onto what I coach, strength training plus consistent daily movement, with moderate aerobic work alongside it, not instead of it.

You don't need Zone 4 or 5 for basic heart health. Those zones build athletic performance and top-end capacity, valuable if you're training for a specific event, less necessary if your goal is cardiovascular health and longevity.

What this means if you're already strength training

If you're lifting two to three days a week and your daily movement is consistent, 6-8K steps at a purposeful pace, not a slow stroll, you're likely already accumulating meaningful Zone 2 time without labeling it as such. The talk test is still the authority: if you're moving at a pace where you could hold a real conversation, you're in Zone 2. A leisurely window-shopping pace probably isn't. A purposeful walk to the train station probably is.

If you're anxious about cardiovascular health specifically and want to be more intentional: start with your existing routine and find the gaps. Where are you currently sitting still that you could be walking? That's usually the answer before any structured cardio program.

The bottom line

Zone 2 isn't complicated once you strip away the jargon. It's a sustained, conversational pace that builds your aerobic engine in a way strength training doesn't, and it doesn't require a heart rate monitor, a treadmill program, or any new equipment. It requires moving at a pace where you could talk, consistently, for 150 minutes a week.

For most of the women I work with, that's not a new program. It's walking more than they currently are.

If you want help figuring out where this fits in your specific routine, or whether you're already getting more of it than you think, that's exactly what a first conversation is for. Book a free Wellness Strategy Session.