‘Zone In’ for Cardio that Works

Whenever I start talking to clients about ‘cardio,’ responses typically fall into one of three categories:

1. Cardio is life (and they tend to do too much; often too high-intensity)
2. Cardio sucks (and they tend to do too little or none)
3. I do cardio because I sort of think I have to (but they aren’t quite sure if they’re doing enough, too much, or even what kind of cardio is ‘worth it’ to do)

With the Type 1 clients (aka the “cardio bunnies,” the HIIT addicts, the Spin-classers), I find myself trying to explain the importance of moderate-intensity cardio and not blowing past their anaerobic threshold (or worse, getting injured from all the jumping around).

With the Type 2 clients (aka the “heavy lifters,” the ones that skip all cardio for fear of losing their gainz), I find myself trying to explain the importance of regular cardiovascular exercise for heart health, and why some level of cardio is helpful for body recomposition if that is also a goal.

And with the Type 3 clients (aka “everyone else,” the people who are a little confused about the role of cardio in a regular exercise program), I find myself trying to advise around everything from F45 to marathon running to hot Pilates to answer the question, “what’s the ‘best’ kind of cardio to do?”

Luckily, there’s a singular answer for all three types of folks, and it’s backed by science: ZONE 2 cardio.

“Zone 2” exercise has gotten a lot of press lately as the cardio format du jour of experts like Peter Attia. The idea is that at a specific “zone” of intensity (measured most accurately by indirect calorimetry testing, or VO2Max), your mitochondrial activity is stimulated the most – meaning you burn the most fat (versus carbs) for fuel.

Sounds great, right?

Problem is, most recreational athletes are jumping straight to higher Zones – think 3, 4, and 5 – which burn primarily carbs for fuel, missing out on the mitochondrial and fat-burning benefits of zone 2 entirely.

The great – and confusing, to seasoned exercisers – thing about Zone 2 cardio is that it isn’t actually painful, and it doesn’t take any great efforts to achieve. In fact, most professional (think Olympian) runners spend 80% of their training time in Zone 2 – meaning that, contrary to popular belief, what separates the pros from the amateurs is that they spend more time going slow and easy (relative to their own respective training abilities, of course).

So how does this apply to us non-Olympians out here just tryin’ to get lean and fit?

It means that if one of your top fitness goals is to lose body fat, Zone 2 cardio is the most effective form of cardio to help you do that. Take note:

If you’re really committed to knowing your exact, personalised Zone 2 threshold (because, yes, it is highly individualised depending on a variety of factors), your best bet is to schedule a VO2Max test at LIFT Clinic and find out the exact intensity of exercise at which your body burns fat for fuel (as well as the exact point at which it stops doing that, so that you can stay beneath that level if fat burn is your main goal).

If you want an easier approximation of Zone 2 effort, you can use your heart rate (Apple Watches and other trackers automatically record this data when you log your workouts – check the “heart rate” section of your Activity app afterwards to see your zones!). A “Zone 2” heart rate is generally 68-82% of your maximum heart rate, which you can approximate here (this calculator calls it the “moderate aerobic zone”).

If you want something even easier than that, consider the “talk test” – if you were on a phone call while performing Zone 2 exercise, the person on the other end of the line should be able to tell you’re exercising, but you wouldn’t be so out of breath you can’t talk comfortably for the full hour.

…which, yeah, brings me to my next point.

Ideally, you’ll need to perform Zone 2 cardio for 45-60 minutes per bout, for a total of 120-180 minutes per week. The minimum effective dose is 45 minutes per bout, so this isn’t one of those “break it up throughout the day” things – to get your mitochondria really rockin’, you need to hit the 45-60 minute minimum duration, and maintain Zone 2 intensity throughout (no fair dropping down to Zone 1 to “recover” or pushing hard to Zones 3 and 4 to “get that burn”).

A final note on Zone 2, in case I haven’t convinced you of its necessity already – Zone 2 cardio can be any form of cardio, as long as it’s steady & sustainable for 45-60 minutes for you personally. You can swim, bike, hike, row, dance or ruck your way into Zone 2 – just make sure you stay there, and its engaging enough for you to (at least somewhat) enjoy.

Coming back to my three types of clients – as you can tell, there is a “best practice” when it comes to cardio, and it’s a bit of a blend of all three approaches. You need some (not none), you need it to be moderate intensity (not too high, not too low), and you need to do it 120-180 minutes per week (an exact amount) to get the max benefits.

Now take your marching orders and get Zone 2-ing!