In the fitness and exercise world the impression is: the harder you train the better your results and the more fat you can burn. There is no shortage of motivational quotes insinuating as much; but is that what the research suggests is best for our overall health, longevity, muscle mass or fat loss? Here, we will explore Zone 2 training and help determine whether it is the best regimen for you.

Exercising on equipment

Aerobic exercise that you can do to burn fat

Based on the work of Inigo San Millan, Ph. D., Assistant Professor at the University of Colorado and 25 year veteran in training elite athletes, and Phil Maffetone, health practitioner, internationally recognized researcher and author, it appears that regular (3-4 times a week) lower intensity exercise for longer periods of time (45-90 minutes) is best both for improving performance and reducing injury in elite athletes, but also for improving fat burn, preserving muscle mass and overall health and longevity for normal people (ie us non-elite athletes) as well. This type of exercise is known as Zone 2 training.

As a physician and recreational athlete, I have told myself and my patients in the past that training at a higher intensity for longer periods of time was better. During my medical training I ran 7 miles a day in the hopes of losing some weight. However, I noticed both in myself (and later in my patient population) that exercise rarely produced significant weight loss or fat loss. I just kept telling myself, “If only I could run faster for longer I would get leaner.” The only thing I really saw from all those years of running 7 miles a day was premature arthritis in my knees. To be fair I do feel that the running helped me maintain my weight and cardiovascular conditioning.

After seeing no improvement in my body fat or muscle mass and having more pain, I stopped running in my early 40’s to focus more on resistance training. I also told my patients that based on my experience and the best medical literature available to me at the time, that exercise was not a very effective way to lose weight. Many of them were quite pleased to hear that I wasn’t pushing them to exercise; I cringe now thinking of how many people avoided exercise because I gave them the impression that the diet mattered more.

But now, after coming to understand and appreciate all the benefits of Zone 2 training (and resistance training which I will get to next week) I have changed my tune. I feel that we should all be doing Zone 2 training for fat loss, preservation of muscle mass and improving overall health and wellness.

What is Zone 2 training?

So what is Zone 2 training? It is the maximal level of aerobic exercise that you can do to burn fat inside the mitochondria of your cells (the powerhouse inside your cells where most of your energy is produced) before you cross over into anaerobic exercise and start burning more glucose (and therefore less fat) outside of the mitochondria. When you burn fat instead of glucose your mitochondrial utilization is maximized.

And why does this matter? Because when you are in Zone 2, using your mitochondria at maximum capacity, this acts as a signal for your body to grow more mitochondria. If you grow more mitochondria, you develop a faster, healthier metabolism that can burn more fat, preserve more muscle mass, both while exercising and while at rest. This can help with weight loss/fat loss, improve blood sugar control and help protect you against diseases like obesity, heart disease, diabetes, dementia and cancer.

And why can’t you achieve this with regular high intensity exercise like HIIT, fast running, fast rowing, fast swimming, etc? Because when you perform these higher intensity exercises you transition out of Zone 2, to Zone 3 and higher. This means you transition from burning fat to burning glucose. This is a much more difficult state for your body to maintain, it utilizes less mitochondria and as a result does not stimulate your body to grow more mitochondria.

If you aren’t growing more mitochondria you have a less aggressive (slower) metabolism. Additionally, higher intensity exercise causes more inflammation which can also slow your metabolism, eat away at your muscle mass and increases your risk for injury.

One of my favorite strength and conditioning coaches recently wrote, ”I love HIIT….BUT it doesn’t really do much for maintenance of lean mass or strength. It can actually be counterproductive for #gainz and turn it in the opposite direction. I have seen several HIIT enthusiasts with very low lean mass, pretty high body fat and a plethora of orthopedic issues.” Beth Lewis.

So if you should train in Zone 2 for maximal fat burn, protection of your muscle mass and improvement of your metabolism, how do you know if you are in Zone 2?

How do I test to determine if a Zone 2 regimen is best for me?

There are two ways to test for Zone 2 exercise. The easier way is based on Phil Maffetone’s work. He recommends that you take the number 180 and minus your age to get your Zone 2 heart rate goal in beats per minute. He also recommends that if you are recovering from a major illness, are on any regular prescription medication or you have been overtraining subtract another 10 points from your heart rate goal. If you have a mild injury, get colds and flu more than twice a year, have seasonal allergies or asthma or are over fat (waist circumference is more than half of your height), or you are just starting or have stopped exercise recently, subtract 5 points from your heart rate goal.

An example: a 45 year old person who exercises regularly with high blood pressure on a medication with seasonal allergies would calculate as follows: 180 – 45(age) – 10(on medication) – 5(seasonal allergies)= 120 beats per minute as your Zone 2 heart rate goal. This person would want to keep their heart rate at around 110-120 (not over 120) beats per minute for the entire 45-90 minutes of their Zone 2 training.

The more accurate but also more difficult way to tell if you are in Zone 2 is to test your lactic acid levels. This is not currently readily available to the public, but we are working on a protocol for release to the public soon!

Once you have figured out your Zone 2 heart rate goal, it is recommended that you perform Zone 2 training 3-4 times a week for 45-90 minutes. For example, I will do my zone 2 training today. I am 43 and take no medications and exercise regularly. My heart rate goal should be at 137 beats per minute (or slightly less) during my Zone 2 training and I will do this for 45 minutes today on my stationary bike. Compared to my previous “go hard or go home” cardio days, the intensity of this session will be much lower and my knees will thank me!

P.S. HIIT or higher intensity exercise is still recommended but in small quantities (like once a week) for as little as 20 minutes to receive the benefit without the disadvantages.

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