Zone 2 Training

What is Zone 2 Training?

Zone 2 training strengthens the mitochondria in our cells. You may remember learning in 8th-grade biology that mitochondria are the powerhouses of our cells, responsible for producing energy (ATP). These cellular engines generate energy by burning both fat and glucose. Maintaining the health of these structures is essential for metabolic health, brain function, and controlling inflammation and oxidative stress.

Zone 2 training is one of the five (sometimes six) zones described in cardiovascular exercise. These zones correspond to different levels of output and heart rate. To simplify: Zone 1 is akin to a leisurely walk in the park, while Zone 5 is an all-out sprint up a hill that leaves you gasping for air. Zone 2 lies in the middle, characterized by an intensity where you can hold a conversation, though some sentences may feel slightly strained.

Why to Zone 2

The better trained you are in Zone 2, the more powerful your mitochondria become. By improving your mitochondrial efficiency and number, your body is better able to produce ATP – the energy source required for all cellular function. This boost in mitochondrial health acts as a strong foundation for your fitness, making it possible to push harder in more intense exercise or allow you to have an extra gear when life throws you a curveball like having to sprint to your terminal at the airport.

Zone 2 training optimizes your body’s ability to burn fat as fuel. At Zone 2 intensity, your muscles rely predominantly on fat oxidation and prefer to store glucose for when it is needed most. The ability for your body to change from one fuel source to another is called “Metabolic Flexibility” and is something that we should all strive for. The enhanced metabolic flexibility that comes with Zone 2 training will support weight management, improve glucose regulation, and increase endurance because your body is able to produce energy from fat – our bodies most abundant and energy rich fuel source.

Zone 2 training adapts to your fitness level over time. For example, just six weeks ago, my Zone 2 runs had me jogging at an 11:30 per mile pace, with frequent stops to lower my heart rate. By consistently training in Zone 2, I can now sustain a 9:30 per mile pace without exceeding my Zone 2 heart rate—a two-minute improvement in only six weeks! Increased aerobic fitness from Zone 2 training translates into better endurance for everyday activities, such as playing with your kids without feeling out of breath, walking around all day while shopping, or enjoying an active day out without fatigue.

How to Zone 2

Finding your Zone 2 can be done easily using the “talk test.” If you can speak in complete sentences but find it slightly challenging to hold a long conversation, you are likely in Zone 2. If you’re gasping for air and unable to complete sentences, you’re in Zone 3 or Zone 4. Conversely, if you can chat effortlessly, you’re in Zone 1. Another method is heart rate monitoring, with Zone 2 typically falling between 70% and 85% of your maximum heart rate (see the end of this article for my Zone 2 calculations as an example).

Once you’ve identified your Zone 2, choose an exercise that fits your lifestyle and preferences, allowing you to maintain a steady pace. For example, I do much of my Zone 2 training by jogging, but I have recently added stationary biking, rowing, and the stair stepper to minimize the impact on joints. Many people achieve Zone 2 intensity with a brisk walk, while others may require a light jog. As you progress you may find that you need to change your methods or slightly increase the intensity you are exercising at to avoid falling back into Zone 1.

An excellent (and lofty) weekly goal is to accumulate 180 minutes of Zone 2 training per week. However, even as little as 60 minutes weekly can yield benefits, especially if you are new to this type of exercise. You can break up your Zone 2 training however you like. I currently spread it across four sessions of 30–45 minutes each. Use this time to listen to an audiobook or podcast, plan your day, connect with a loved one, or simply enjoy a mental break from the fast-paced, overstimulating world around you.

Example on How to Calculate Zone 2

Heart Rate Max HR = 192 bpm (according to my Garmin smartwatch)

Lower end of zone 2 : 70% x 192 bpm = 134 bpm

Upper end of zone 2 : 85% x 192 bpm = 163 bpm

So my goal when zone 2 training is to stay someone in between 134 – 163 bpm zone. If I find the effort feels a little to hard or I am not wearing a HR monitoring device I will just try to hold a short conversation with myself (probably look insane to people passing) and use this as a guide to get me into zone 2. If I’m on a run and my HR starts to elevate out of zone 2 I just stop and walk for a bit.

Stay Healthy,

Thomas Stevens