What’s the Deal with Zone 2 Cardio?
Cardiovascular exercise, in general, is divided into four zones, defined by the rough percentage of your max heart rate (MHR) that your heart is beating at while you’re working out. They are as follows:
Zone 1 (very light): 50-60% MHR
Zone 2 (light): 60-70% MHR
Zone 3 (moderate): 70-80% MHR
Zone 4 (hard): 80-90% MHR
These zones are important to know and understand when designing a cardio workout program, as they all serve a specific purpose, but for today we’re just going to focus on Zone 2, or, as I like to call it, The Infinity Zone.
Enter The Infinity Zone
As per usual, we’ll get to the practical first: how to do the exercise. In this case, the first thing you need to do is find your max heart rate. While there are a bunch of fancy test options in sports labs to figure this out exactly, there’s also a simple formula for estimating it that’s more than accurate enough for our purposes. That formula is…
208- (0.7 x your age)=your estimate max heart rate
So for me, it’s 208 – (0.7 x 35) = 183.5 Beats Per Minute
Which means, for zone 2 cardio, I should doing some activity that keeps my heart between 60-70% of that, OR 110-128 heartbeats per minute.
“But Dan,” you say, “What if I’m not wearing a fancy heart rate monitor while working out?”
Good question! In that case, a good estimation of zone 2 cardio is “elevated heart rate, but still able to hold a conversation.” Meaning if you’re moving at an intensity that’s enough to increase your breathing and heart rate noticeably, but NOT to the point where you can’t comfortably have a conversation with someone. Basically, you want to be breathing a bit heavier, but never gasping for air.
The other element of good zone 2 cardio is time. In order to really be effective, zone 2 cardio should be performed for at least 45-60 minutes without break (we’ll get to the “why” a little later.) Additionally, you should be shooting for at least two zone 2 cardio sessions a week (again, we’ll talk bout the “why” for this in a minute.)
Finally, there’s the “how,” and that one’s basically up to you! My favorite zone 2 cardio exercises are ruck walks with my weighted vest, or light trail running sessions, but the choice is really up to you! You just need to pick a low impact activity that you can do for a long time. Cycling, elliptical, and rowing can all be great options as well, or just going for a regular old walk!
So now that you know the how (45-60 minutes of elevated heart rate but still talking pace cardio twice per week,) we can move on to the why.
The Heart is a Muscle, Too!
Of course, the idea of the heart being a muscle isn’t a new one, but have you ever thought about how one trains that muscle? You can’t make your heart hold a dumbbell or pull on resistance bands. The answer is, of course, by making it beat more. Zone 2 cardio gives a unique opportunity in that it allows your heart rate to stay elevated for an extended period of time. Your heart is accustomed to working constantly, obviously, so it can be difficult to push it to the point where you’re actually shocking the cells enough to make it adapt.
Sure, sprints and other things in higher cardio zones make your heart work hard, and that’s ONE way to work out your heart muscle, but it’s very explosive and intense, so it’s not going to build your heart’s stamina or muscular endurance. Zone 2 cardio allows you to elevate your heart rate for an extended period of time, building your heart’s overall capacity for an increased workload. This means the rest of your body also gains the capacity for increased workload (since the muscle responsible for getting blood to them has a higher capacity for pumping.)
The reason why I refer to Zone 2 cardio as “The Infinity Zone” is because increasing your heart’s capabilities enough enables you to perform athletic activities, functionally, “forever.”
The Mitochondria is the Powerhouse of the Cell
Making your heart stronger and more efficient isn’t the only long term physiological benefit of zone 2 cardio! I’m sure many (MANY) of us remember learning about mitochondria back in grade school, but for those who don’t, here’s a brief refresher. Mitochondria are the cell structures responsible for producing adenosine triphosphate (ATP), the “fuel” that powers basically every cellular function in your body (including your muscle tissue.) Zone 2 cardio not only increases the size and capability of existing mitochondrial matrices, it also increases the overall number of mitochondrial structures in your body as well!
Basically, this means your body gets way better at producing energy from both the food your consume and the fat your body already has stored inside it, making your muscles more efficient, raising your overall energy levels, and even improving your cognitive functions.
Speaking of fat…
Zone 2 is Also Known As “The Fat Burn Zone.”
We are very much a body positive fitness site, however we also believe there are plenty of mentally healthy reasons for losing body fat, if you choose to do so. Zone 2 cardio is particularly good at this function, and next to increasing your overall metabolism through lean muscle mass, it’s probably the best activity for burning body fat. This is, again, because of the nature of how your body produces energy. For the first few minutes of exercise, your body relies on the glucose that’s already existing in your muscles and bloodstream for energy, through various anaerobic methods. However, once you clear these temporary, short-term energy stores, your body starts using what’s known as the “oxidative energy system.”
To oversimplify the idea a bit, once you’ve used your short term energy supply, your body starts to break down fat cells for longer term energy options, capable of sustaining you for long periods of time. They’re generally not used for short term, high intensity activity, but low intensity, long term cardio is basically the reason your body stores fat. We’re built to be long distance pursuit predators and migration specialists. Zone 2 cardio causes all of these systems to fire up and use those long term energy stores (body fat,) to keep you going through long, low-impact activities. As such, adding in some extra zone 2 cardio is the best way to increase your overall fat burn in a week without significantly increasing hunger cues.
But Doesn’t Cardio Kill Gains?
So, if you only do zone 2 cardio, your body will start to utilize unneeded muscle tissue as a source of fuel (losing some of your gains.) However, this is super easy to prevent just by engaging in regular resistance training (weightlifting, bodyweight exercises, etc.) Basically, your body tries not to break down anything it needs to use regularly, and by regularly engaging your muscles in resistance training, your body will work to hold on to the muscle tissue even if you’re performing zone 2 cardio a couple of times a week. In fact, through the above mentioned adaptations you’ll gain through zone 2 cardio, your muscles will actually see an overall performance increase!
Let’s wrap it up!
In short: If you want to become a real life superhero, do zone 2 cardio. One hour, twice a week, get it done.
That’s it.
Live boldly, change the world, and continue to be awesome!
Dan Wallace
