by Valerie Demetros
Zone 2 training is one of the most important, and underrated, training forms.
Experts define zone 2 as keeping your heart rate between about 70% and 80% of its maximum, meaning it’s an easier run in which you can maintain a conversation.
Your body depends on adenosine triphosphate (ATP), the molecules in your body that give you energy. What you eat also gives your body the fuel to create ATP. Further, you create more ATP as you exercise.
Which type of fuel your body uses is determined by which heart-rate zone you’re in.
Sports scientists classified the six heart-rate zones and which energy sources they use. For reference, zone 1 is scrolling Instagram while sitting and zone 6 is an all-out sprint.
Zones 1 and 2 use fat and oxygen for energy. Zone 3 uses fat and carbohydrates while zones 4 and 5 use just carbohydrates. Finally, zone 6 uses mainly carbohydrates and creatine phosphate.
Since zone 2 training uses fat (and some oxygen) as its energy source, this is why it doesn’t feel as hard as zone 3 or above.
Usually spin classes, HIIT workouts and runs are done above zone 2. But even though it doesn’t feel hard enough, you could be missing out on some great benefits.
Working out in zone 2 can improve your aerobic base. Improving your ability to exercise with a lowered heart rate without going up a zone can increase your capacity to work at higher intensities by making your cardiovascular system stronger.
This enables you to take on more training load because you’ll have a stronger aerobic capacity, making the harder workouts feel easier.
Zone 2 workouts also increase your mitochondrial function and density. Mitochondria are the generator of your cells, producing chemical energy using oxygen.
The healthier your mitochondria the better. Mitochondrial dysfunction is seen in people with heart disease, dementia, Type 2 diabetes, metabolic syndrome, cancer and obesity. Mitochondrial dysfunction also is a root cause of insulin resistance.
Zone 2 training increases the number of mitochondria you have and how efficiently they work by stimulating the production of oxygen. If you surpass zone 2 and train harder, your body starts to use carbs to create adenosine triphosphate.
By working different energy systems in your body through a variety of heart rate zones, your body becomes more adept at switching between these fuel sources. With zone 2 training, your body becomes more familiar with burning fat for energy.
Another important benefit of zone 2 training is that it lowers your resting heart rate.
This means your body manages higher intensities easier. And with a larger aerobic capacity, you are better able to flush out lactic acid, which builds up in your muscles and causes DOMS (delayed onset muscle soreness).
This means you can go again earlier and push consecutive sets of training harder.