What is Zone 2 Cardio?

Zone 2 cardio is the easiest, but most boring form of cardio exercise.  However, it is the best place to start when building your cardiovascular fitness foundation.

In fact, anyone looking to improve their overall fitness and wellness should incorporate Zone 2 cardio into their training.  It is included in the Optimal Wellness System I’ve put together.

Cardio conditioning is generally broken down into five levels, with Zone 1 being the lowest and easiest level, akin to going for a walk, to Zone 5 (or 6, depending on who you are talking to), which involves the most intense and exhaustive effort.

These training zones are based upon your heart rate as you are training.  The higher the rate, the higher the zone.

Zone 2 training is done with a heart rate that is around 60% to 70% of your maximum heart rate.

Zone 2 has been identified as the level that is most efficient at burning fat, building long term stamina and endurance, and improving longevity.

To understand how Zone 2 cardio works, it is necessary to understand how your body uses food to power your existence.

ATP

ATP stands for adenosine triphosphate, the molecule that mediates energy exchange in living systems.

Nothing gets done without it. Sugars and fats may be the source of energy for the cell, but that energy has to be in the form of ATP to get used.

When a cell needs to do something or make something, it can’t just spend a sugar or fat molecule. The energy in food must be captured in the form of ATP for the energy to be spent.

Glycolysis (Step 1) splits glucose to yield ATP (Adenosine Triphosphate), high-energy electrons and pyruvate.

Pyruvate, electrons and fat all enter the mitochondrion. Pyruvate is “burned” in the Krebs Cycle (Step 2), producing a little ATP and a lot more hot electrons.

Fat is “burned” in the beta oxidation cycle (another Step 2), also producing electrons and fragments for the Krebs Cycle.

Electrons from glycolysis, Krebs Cycle, and beta oxidation are funneled into the ETS, where they are used with oxygen for oxidative phosphorylation and the production of a bounty of 32 ATPs (Step 3) from 1 glucose alone.

Most of the ATP ends up in the cytoplasm, where it is used to do work. So used, it can be rapidly recharged by the creatine cycle. Please note: everything happening inside the mitochondrion is aerobic. Everything happening outside the mitochondrion is anaerobic.

Yet the ATP produced by all these processes fills a common energy pool, and all of these processes work together.

Over the years, exercise scientists have developed “training zones” to help athletes and coaches understand which energy systems and muscle fibers they’re using at a given exercise intensity level.

One such system divides training intensity into six zones. Zone 1 is the lowest intensity (sitting down, walking around your house, etc.), and Zone 6 is the highest intensity (all-out sprinting, deadlifting a heavy set of five, etc.).

• Zone 1
  • Energy source mainly used: fat
• Zone 2
  • Energy source mainly used: fat trending into carbohydrates
• Zone 3
  • Energy source mainly used: fat trending into carbohydrates
• Zone 4
  • Energy source mainly used: carbohydrates
• Zone 5
  • Energy source mainly used: carbohydrates
• Zone 6
  • Energy source mainly used: carbohydrates trending into creatine phosphate

As you can see, the type of fuel your body uses to create ATP changes as you go up in intensity.

Jogging is typically done by most people in Zones 3 and 4

In zones 1 and 2, you’re using primarily fat. As you shift to Zone 3, you start using carbohydrates.

When you reach zone 6, you use creatine phosphate to create ATP.

In Zone 2, your exercise intensity is at a level in which you are stimulating your cells’ mitochondrial function the most.

It’s at this level where the mitochondrial function becomes more efficient and production of new mitochondria is stimulated.

For the trainee, the beauty of Zone 2 cardio is that it is easy to do.

Unfortunately, most people who do cardio exercise tend to work in Zones 3 and above.  The thinking is that training harder burns more calories.

The problem is they get burned out from this type of work fairly quickly and then stop training.

Zone 2 provides a solution to that problem.  Now let’s look at some of the benefits of Zone 2 cardio exercise.

Benefits of Zone 2 Cardio

Improves mitochondrial function. Zone 2 is the level at which you’re stimulating your mitochondria the most to create ATP.

As you spend more time in Zone 2, your body will respond by creating more mitochondria to power your Zone 2 activity.

The more mitochondria you have, the more you’re able to create ATP through fat oxidation.

Zone 2 training not only increases the number of your mitochondria, but it improves their efficiency as well.

The more you exercise in Zone 2, the better your body gets at burning fat for energy.

Improves your performance as an endurance athlete.  Zone 2 cardio has been used for decades by elite athletes.

In fact, most elite endurance athletes train in Zone 2 upwards of 75% of the time.

The reason for this is that it creates a foundation of cardiovascular endurance that builds over time.

The more you do, the longer you will be able to train in higher zones.

Improves cardiovascular health. Besides exercising your mitochondria, Zone 2 cardio also gives your heart and blood system a workout.

Over time, your heart will get stronger and become more efficient.

Your body also expands its vascular system, better enabling it to deliver oxygenated blood to the different parts of your body.

This improvement in cardiovascular fitness will result in better performance when exercising as well as a lower resting heart rate.

Improves work capacity. This is something I’ve personally noticed since I started incorporating Zone 2 cardio into my own program.

Zone 2 cardio can help you recover more quickly between lifting sets which in turn can allow you to do more work in a training session.

Aids recovery. Zone 2 cardio also serves as great “active recovery exercise.”

When you’re in Zone 2, you get the blood pumping, which delivers nutrients to your muscles to help them bounce back from a weightlifting session.

I find it most useful to do a Zone 2 session on an exercise bike the day after I train the legs hard in the weight room.

How to do Zone 2 Cardio

Unfortunately, the best way to do a Zone 2 workout is indoors on a bike, elliptical, treadmill or rower where you can stay at an even pace for the entire workout.

This effectively means that Zone 2 cardio workouts are pretty boring.

You need to be able to stay at the same pace to keep your heart rate in Zone 2, which is about 60%-70% of your maximum heart rate.  Otherwise, if you start to creep up into Zone 3, you’ll stop burning fat and start using carbs for the energy source.

A rough way to calculate your maximum heart rate is to subtract your age from 220.  Then, multiply that figure by 70% to get your top line Zone 2 figure.

So, if you are 50 years old, your maximum heart rate will be somewhere around 170.  If you are in pretty good cardio shape already, it may be somewhat higher.  If you are untrained, it may be a good bit lower.

Therefore, the high figure for your Zone 2 will be around 120, if you are 50 through this calculation.  However, I think this is likely a bit low, based on experience.

An even more simple way is to come up with your top Zone 2 figure is to subtract your age from 180.

A good rule of thumb is that when doing Zone 2 cardio, you can have a conversation by talking in one or two sentences, but it will be difficult for you to sing for more than a minute or so.

You should also be able to breathe completely through your nose.

I do my Zone 2 Cardio on an indoor bike where I pedal at the same level of resistance at the same level of RPMs.

You can achieve something similar on just about any piece of indoor cardio equipment.

How much Zone 2 do you need?

The best information I have found on this subject suggests that you need a minimum of 2 hours of Zone 2 Cardio per week to start getting the most benefit (i.e., the mitochondrial efficiency).

The ideal range is 3 to 4 hours, and the ideal session length is 60 to 90 minutes.

With that said, you will still get some benefit with shorter sessions, but you will need them to be at least 30 minutes.

Personally, I have not been able to fit 3 hours of Zone 2 cardio per week into my schedule.

I typically do two sessions per week lasting from 45 to 75 minutes, and one higher intensity cardio session.

This has worked well enough for me.

If you are new to fitness training, start out by trying to get in three sessions of Zone 2 cardio per week at 30 minutes per session and build from there.

Over time, increase the length of your sessions and play around with other training protocols to see what works for you.

By the way, if you are looking for a decent machine for Zone 2 work, I use a Schwinn Recumbent Bike found on Amazon.  This one is a newer version.

Now, get to work!