Ever wondered how hard you should be exerting yourself during aerobic activity? It feels good to get moving, but should you be dripping sweat and gasping for air after every workout? Is it good to feel the burn while you exercise? Should you follow your heart rate zones, or just keep pushing yourself? How can you maximize your time spent doing cardio for both fitness and health?
These are all great questions, and we hope to shed some light on one of the most efficient ways to go about your aerobic activity. We’d like to introduce you to one of our favorite forms of exercise: Zone 2 exercise. Zone 2 exercise has wide ranging benefits but is also extremely easy to do. So, what is it?
Brief Refresher of Our Energy Systems…
You may have heard that we have two types of muscles in our bodies: fast twitch and slow twitch.
Slow twitch muscles are packed with mitochondria, which are tiny fuel cells in our body that create energy in the form of a molecule called ATP. Mitochondria create ATP by burning sugar, fat, and in times of starvation, protein. For the most part though they burn sugar and fat, often preferring fat due to the higher energy yield. Our bodies rely on high functioning mitochondria in order to maintain all of the body’s energy demands throughout the day. Without mitochondria, we would not exist!
Fast twitch muscles contain little to no mitochondria, meaning they rely solely on a third, much less efficient method of energy production by way of sugar only burning. This process, known as glycolysis, takes place outside of the mitochondria and creates ATP very quickly (like during a sprint or high intensity exercise) when we are burning energy at a high rate. The result of this process is that our bodies create lactate (often called lactic acid) as a byproduct which is responsible for that burning feeling in our muscles and longer recovery time after exercise. It is not a sustainable form of energy production.
More research is supporting the idea that poor mitochondrial function is a root cause of many chronic illnesses of today (diabetes, cancer, Long COVID, heart disease, obesity).
But I thought burning sugar is good?
Well, yes; when your mitochondria burn sugar it can be a good fuel source. But when our mitochondria are not working efficiently, we rely too much on glycolysis during exercise, which would normally be our body’s last resort to make energy. Depending on the degree of mitochondrial dysfunction, we may exceed our mitochondria’s ability to produce energy even during light bouts of exercise, which is not good.
To make matters worse…
When our mitochondria cannot keep up with the energy demands during exercise, our liver responds by sending out a continuous stream of sugar into the bloodstream in order to keep up with the high demand. While this might be good if we were running away from a tiger, when exercising for health and longevity it is not necessarily a good thing.
The reason this is not a good thing:
When blood sugar goes up so does your insulin, which over time can lead to metabolic dysfunction and weight gain. Keeping your insulin spikes down has benefits ranging from weight loss, improved diabetes control, and lower rates of cancer. To learn more about the importance of insulin, read our post about insulin resistance.
Who Should Do Zone 2 Exercise and Why?
The short answer is… everyone! The longer answer is anyone looking to improve their mitochondrial function (Hint: this should be everyone).
Due to natural aging and chronic inflammation, our mitochondria start to shrink and become less densely packed in our cells as we get older. This results in weaker mitochondrial function and has serious effects on our long-term health.
Mitochondrial dysfunction is associated with numerous diseases that include:
- Cancer
- Insulin resistance and Type II Diabetes
- Heart disease
- Alzheimer’s Disease
- Chronic Fatigue
Recent studies have found that individuals with long COVID show signs of compromised mitochondrial function, playing a role in many of the debilitating symptoms they are experiencing.
That said, when working properly our mitochondria play an immensely important role in optimizing:
- Heart health
- Weight loss
- Decreasing inflammation
- Brain function
- Metabolic health and healthy blood sugar levels
- Our liver and kidneys’ ability to detoxify appropriately
- Skin health
- Minimizing wrinkles and the cosmetic effects of aging
- Workouts and recovery from workouts
- Maintaining muscle mass
So What is Zone 2 and How Do You Find It?
*It is important to note that this Zone 2 exercise is different than the heart rate zones you might see on your smart watch or training app. This can be very confusing because they have the same name, but for now forget about heart rate.
Zone 2 exercise is the point of exertion where we are maximizing the amount of work that your slow twitch muscles can do before needing to switch to fast twitch muscles. It is at this point of exertion that we are burning the maximum amount of fat while keeping blood sugar from spiking, resulting in an ideal situation for metabolic health.
If we want to be very scientific and exact about finding your Zone 2, then we would measure your blood lactate levels using a lactate meter (similar to a blood sugar meter) while you exercise. This Zone 2 range is found at the point at which you are keeping your blood lactate levels at or just below a threshold of 2 mmol/L. This is achieved during a “Zone 2 test”. More on this later as it is a bit complicated. But first, let’s start with the easy way to know you are in your zone 2.
The “Talk Test”
The easiest method to find your personal Zone 2 range is to monitor your breathing during exercise. The CDC and “National Center for Chronic Disease Prevention and Heart Disease” have dubbed this method the “Talk Test”. Your Zone 2 target range occurs when you are just starting to get a little bit out of breath during exercise. You should still be able to hold a conversation and speak full sentences, but the person you are talking to can tell you are working out. A more precise way of measuring this form of testing is to choose a 12-15 word sentence. Once you can no longer say that sentence without needing to catch your breath about every 5-6 words, then you are in Zone 2. You will be sweating a little, but it should feel like an all-day pace for you. This method is an excellent alternative to measuring lactate, and the more you practice the better you will get!
Some examples of sentences you can say:
- I absolutely love how I feel when I exercise and move my body.
- I am so grateful for this amazing form of exercise- it almost seems too easy!
- I can feel the happy neurotransmitters releasing when I do my Zone 2 exercise!
- Rose Health Services has helped me learn how to be my own health advocate.
What types of exercises can I do?
The good news is that Zone 2 exercise can be any form of exercise you like. Many folks enjoy brisk walking, jogging, swimming, biking, or using the elliptical. We personally prefer biking because many exercise bikes show your “watts” as you ride. This is helpful because tracking your number of watts is an easy way to keep workload consistent. Once you think you are in Zone 2, then just try and keep your watts right where they are on the bike. This keeps you in the sweet spot.
Other machines define workload in terms of “METS”, which is short for “metabolic equivalent”. Next time you are at the gym, take a look at the machine you are using to try and figure out your workload while you are in Zone 2.
First time trying Zone 2?
To get started, simply pick your aerobic activity of choice and slowly increase your intensity until you start to breathe just a little bit harder. From there, just keep that pace going for as long as you want. Sound boring? We won’t lie, it can be boring. But use your Zone 2 workouts as an opportunity to multi-task! Call up an old friend, listen to a book on tape or a podcast, or even watch TV. Time goes quickly and after a while you might even forget you are exercising.
1. In order to accurately determine your Zone 2 range, we would start by measuring your baseline lactate level after a light warm up. This is done by poking your finger with a certain type of needle, called a lancet, and collecting a small blood sample using the lactate meter. We would record this baseline lactate number for future reference.
