Zone 2 Exercise - The "Fat Burning" Zone

By: Dr. Gary Huber

Posted 09/27/2021

What is Zone 2 Training? It’s simple. Those of us that exercise live longer, healthier lives. We have less risk for diabetes, heart disease, Alzheimers and yes even cancer. We essentially all know this to some degree. But what constitutes “exercise”? Let’s look at one simple aspect of exercise which is “exertion” measured as heart rate.

Physiologically we divide exercise intensity into 5 different heart rate zones. These zones are a general start point for discussion, but your age and overall fitness will move them left or right quite a bit.

First, we should calculate your maximal heart rate using the following equation:

  • 220 – age = maximum heart rate.

This is merely a physiologic guess based on age alone and could be way off if you are in great shape. It also doesn’t account for genetic differences as some people run a lower or higher baseline resting heart rate. But let’s use a 50-year-old man as our example for the sake of demonstration.   220 – 50 = 170.  No this doesn't mean a 50-year-old man will die if he exceeds 170 beats per minute and no he won’t have a heart attack either. Yes, this is safe to exercise towards. The 170 mark is simply setting expectation of what is possible. Most people will never push themselves hard enough to ever see 170. If you do, then congrats . . . you are a bad ass.

Zone 1 training: This is nothing more than “activity” for most people. If you work a job with heavy lifting or if you are doing yard work, you might get your heart rate into this zone. For those of you who say “walking is my exercise” just know that this is barely exercise and will not contribute greatly to longevity. That's doesn't mean you should stop walking but consider elevating your game a bit.

  • Zone 1 is 50-60% of your Max - so in our example for a 50 year old this would translate to 85 to 102 beats per minute. Not very difficult.
  • Rate of perceived exertion is only a 1-2 out of 10

Zone 2 training: There are 2 ways to calculate zone 2 and some varied opinion on how high this should be. You are not exceeding lactate threshold which is the rate of exertion where you begin to accumulate lactic acid. The benefit of zone 2 is that although it is not terribly grueling, it is stimulating your mitochondria to make ATP and forcing your cell to increase the number of mitochondria you have. This has tremendous benefit for overall health, fat burning, and sets the stage for tougher workouts later. It’s your base upon which all good athletes rely.

The exertion level in Zone 2 is low enough that your body can provide a good portion of the energy you need from burning fat. This is why it is called the fat burning zone. As you intensity or exertional level increases your body becomes more dependent on glycogen (stored sugar) for energy.

  • Zone 2 is 60-70% of your Max = 102 to 119 in our 50 year old example.   
  • Some authors feel it should be up to 80% so this would make it 136

The second way to calculate Zone 2 is using the Phil Maffetone method:

  • 180 – age = x   Then drop it 10 beats to get the range and add 5 beats if well-conditioned
  • 180 – 50 = 130   Range would be 120 to 130. 
  • If in great shape, regular exerciser, then increase it 5 beats to 125-135.
  • If in poor shape or unfamiliar with exercise, then lower it by 5 to 10 beats until you are in better shape.

The goal with Zone 2 training is to exercise at a pace that allows you to sustain your heart rate just below the lactate threshold for a prolonged time period (typically 30 minutes+). This zone is comfortable enough to speak in short sentences and hold a conversation. Most endurance athletes spend about 80% of their training time in Zone 2. This creates an aerobic base where you better utilize fat as fuel. Our goal is to develop better capacity for utilizing FAT as fuel. At higher intensities our body switches over to more carb or glycogen for fuel.

NASAL BREATHING is the goal here. Not so fast that you need to breathe through your mouth. Practice performing this pace with your mouth closed.

Zone 3 & 4 are higher heart rates at 80 to 90% of max and have value for other reasons but that is not the point of our discussion here. Zone 5 is an all-out sprint at 90 to 100% of max which no one can really hold for more than 10 seconds but this has tremendous value for all of us, not just for athletes. We are all athletes . . . hopefully.

Take comfort in knowing that sprints and high intensity are great, but this should constitute a very small fraction of your exercise time. If you engage Zone 2 training the majority of the time you will be laying great groundwork for later acceleration and building cells with tremendous engines to produce energy from your growing mass of mitochondria.

If you are trying to lose weight this is often referred to as the “Fat Burning” zone but don't be fooled by that as there is a lot of fat burning going on in all zones of training. If you are trying to improve your cardiovascular fitness, then blending Zone 2 with periods of Zone 5 is a winning recipe. Whatever your goals, learn your Zone 2 and use it to stay healthy. I reasonable goal is to acquire 120 minutes (at minimum) of Zone 2 training each week. More if you want to continue being a bad ass.

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