So, you want to start a new fitness routine to lose body fat, get leaner, or want more muscle mass. You might be asking yourself, “Should I use the fat-burning zone button on the treadmill?” The theory of the fat-burning zone is that the intensity level required to exercise within this zone burns fat during your workout. There is some science behind this. In this article, we will discuss how to train in Zone 2 and the benefits of this type of exercise. To clarify, you don't need to burn body fat during exercise to lose fat; other proven methods are discussed later in this blog.
When your goal is to lose fat, you must ensure you are doing cardio for heart health, lifting weights to maintain muscle mass, and getting appropriate recovery, sleep, and food to fuel your energy.
This blog will discuss working out in zone 2, a specific intensity you can use during your cardio workout. There are many ways to measure workout intensity; in the laboratory, fitness professionals use methods like oxygen consumption and ventilation, blood lactate kinetics, and metabolic calculations. But for the general population, more practical methods are using heart rate and the talk test to help indicate your workout intensity. We will review both methods, but first, what is zone 2?
What is Zone 2 training?
There is a 5-zone scale based on heart rate regarding your workout intensity. Zones increase from one to five as workout intensity increases from low to high. Zone one is low, and zone five is high. The more intense the workout is, the harder the heart must work to meet the demand from the body, so the heart rate increases as demand increases. Zones help us determine how hard our body is working, and knowing these zones can help train the heart to become more efficient at meeting the demands of exercise, improving fitness.
|Zone 1 – Very light – 50% - 60% HRmax - Speech is unaffected.|
|Zone 2 – Light – 60% - 70% HRmax - Speech is possible.|
|Zone 3 – Moderate – 70% - 80% HRmax - Speech is possible but with some difficulty.|
|Zone 4 – Vigorous – 80% - 90% HRmax - Speech is limited to short phrases.|
|Zone 5 – Maximal – 90%- 100% HRmax - Speech is difficult.|
(Zone chart reference: Marx et al., 2018; Webster & Aznar-Lain, 2008)(1, 2)
We use 2 major energy systems during our workouts, aerobic and anaerobic(3). In zone 2, your body uses the aerobic system, and the aerobic system primarily utilizes fat for fuel. In exercise physiology terms, this is called "fat oxidation"(3). Examples of aerobic exercise are jogging, skiing, swimming, or walking. Examples of anaerobic exercises are lifting heavy weight maxes, all-out sprints, and HIIT training, where muscle glycogen (a.k.a. carbs) is used for energy. Zone 2 is the “fat burning” zone because you rely almost entirely on the aerobic system to provide energy for the workout(4). The aerobic system favorably uses energy from fat stores(4).
Determining Zone 2: Talk Test Method
Zone 2 is where you would be working out in an aerobic state; this means you are in a comfortable workout intensity and can continue for a long time without taking rest breaks. You know you are in zone 2 if you can talk while slightly breathless.
Determining Zone 2: Heart Rate Method
When training with zones, a percentage of your maximal heart rate (HRmax)(5) is used to categorize each zone. Each person’s zone will be specific to them because HRmax is specific to a person’s age. According to the American College of Sports Medicine (ASCM)5, zone 1, the lightest intensity, is working out at 50% of HRmax, up to zone 5 being “maximal” intensity, working at 90 to 100% of HRmax(5, 6).
Some cardio machines, like the treadmill and elliptical, can monitor your heart rate with pulse sensors that detect your pulse through the skin of your hands(7). The sensors are small silver metallic plates located on the support arms of the machine. You can also use wearable technology like a chest strap or smartwatch to monitor your heart rate(8,9).
In zone 2, your heart rate should be 60 - 70% of your HRmax. To figure this out, take the number 220 and subtract your age(5), then multiply the difference by 60-70%. So, if your age is 41, your calculation would look like this: 220-41=179 bpm. Then you calculate for the low and high end of zone 2, 179 bpm x 60% = 107.4 bpm and 179 x 70% = 125.3 bpm. Zone 2 for a 41-year-old would be between 107 and 125 bpm, ensuring they are in zone 2 during their workout.
How to Program It
Zone 2 training is easy; you just need to remember the end goal. When programming for fat loss, you will want to use periodization training. This means you start small in the beginning and work out at least 20 minutes in zone 2 to get the fat-burning benefits. Then, as fitness progresses, workouts progress, too, whether by duration, intensity, or volume. With zone 2 cardio, a beginner should start with about 70% to 80% of their weekly training in zone 2; the person would spend 20% to 30% on other modalities like weight training, depending on fitness levels and goals. Programming zone 2 for fat loss looks like 20 to 30 minutes of zone 2 cardio two to three times a week, walking on the treadmill, or using the elliptical. As fitness increases, the person could increase these cardio bouts to 30 to 40 minutes, and eventually, they will be doing their zone 2 training at home on their own for longer durations. Some people enjoy their cardio and can stay in Zone 2 safely for long periods.
Example Workouts for Beginners
- Warm-up - walk slowly for 5 minutes and practice not holding onto the safety arms
- Walk on the treadmill at a pace that increases your temperature and leaves you a bit out of breath, something like 2.8 mph to 3.8 mph. It should feel brisk. This is where you try the talk test, and listen to your breathing, make sure you are at 60%-70% of your HRmax. You can choose to add a slight incline of up to 2.0
- Stay at this pace/heart rate for at least 20 minutes
- Cool down – walk at a slower pace for 5 minutes before hopping off the treadmill
- Warm-up - jog at a slow pace for 5 minutes
- Jog on the elliptical at a pace that increases your temperature and leaves you a bit out of breath, something like 2.4 mph to 3.4 mph. You should feel breathy. This is where you try the talk test, and listen to your breathing, make sure you are at 60%-70% of your HRmax. You can choose to add a small amount of resistance
- Stay at this pace/heart rate for at least 20 minutes
- Cool down – use a slower pace for 5 minutes before hopping off the elliptical
Zone 2 can be tricky because if you like to go fast, you might go above your target heart rate, kicking you out of zone 2 to a higher zone. You can use the talk test to make sure you can talk; you can also listen to your breathing. If you are gasping for air, you are going too fast. The best way to ensure you stay in zone 2 is by monitoring your heart rate with your wearable technology or simply holding onto the pulse monitors on the treadmill or elliptical.
Beginners vs. Advanced
Beginners will find it difficult to keep their heart rate in zone 2. When you start your cardio regimen, your body has not yet adapted to meet the demands, so your heart rate will tend to be higher than 60-70% of your HRmax. But as you keep training and get fitter, training in level 2 will become easier for you to gauge.
Training in zone 2 five days a week for three months in beginners has been shown to stimulate significant improvements in endurance performance(10, 11, 12, 13). Working out in zone 2 is the highest work rate that can be maintained for an extended period, making it an attractive intensity for daily training(10, 11, 12, 13). Ultimately, zone 2 exercise is an essential and foundational component of a healthy lifestyle(13). Exercise science research suggests that it is one of the best forms of exercise you can do to maintain metabolic health throughout life.
Working in zone 2 will accomplish fat loss for beginners, but keep in mind that as you continue to train, your body adapts to your workout(14). Let’s say you start a two-mile run to lose fat; your body adjusts as you train your run each time. Within weeks, your two-mile run and the work your body needs to finish your run becomes less because you are getting fitter. Your body becomes efficient at your two-mile run, and the only way to improve is to run more miles or finish your two-mile faster. You will eventually reach a point where working harder will send your body into the anaerobic zone, and then you're primarily burning carbs during exercise, rather than fat. Unless you have all day to run in zone 2, most of us have a life we need to tend to.
Advanced training or an option for a shorter workout is to do high-intensity training or HIIT to stimulate fat burning; this works due to EPOC or excess post-exercise oxygen consumption; you might have heard people call this the “afterburn effect.” The theory behind EPOC is that by hitting high intensities in a workout, your body has exhausted energy systems(14). After the workout, your body returns to normal by rebalancing the energy systems, hormones, fuel stores, and repairs cells; this requires a lot of energy and calories after your workout is completed(15).
Zone 2 is familiar to endurance athletes like marathon runners or triathlon athletes. Zone 2 training is essential to improve their performance. Endurance programs have 60-70% of zone 2 training and train in other zones; this is because when an endurance athlete is racing, they will utilize the aerobic systems (fat utilization) for preserving their anaerobic system (glycogen stores) until they need to use it to sprint to the end of the race(16).
Benefits and Downsides
Training in zone 2 will benefit your cardiovascular health and help with weight loss goals. Any fitness level can learn to train in zone 2 safely and become more fit training with zone 2. Studies also report that aerobic fitness increases and the body does not need as much recovery time from training in zone 2 as in higher zones like when HIIT training(17). You can also use zone 2 as a great active recovery day if you are an athlete who typically trains at higher intensities.
Be aware that training in zone 2 can also hinder fat loss. Eventually, the body adapts to your cardio routine, and your cardio workout becomes less effective for fat loss. If you want to continue to lose fat, you must either increase the intensity and train harder, which will not be zone 2 training, or increase the distance, which can make for long, drawn-out cardio workouts. Too much of the same repetitive movement can cause overuse injury, and too much cardio can lead to increased hunger and food intake, which can lead to fat gain(18).
It is also essential to remember that cardio, in conjunction with calorie restriction, can lead to the loss of fat and muscle. After losing muscle, when you decide to return to normal calorie intake, you will replace the lost muscle with fat(18). Losing weight like this can be bad for body composition because your body will burn fewer calories at rest due to loss of muscle mass(19). A pound of muscle burns 6 to 10 calories a day(20).
Keep in mind strength training burns fat too! Muscle is more metabolically active than fat; having more muscle mass means you burn more calories at the same body weight than having less muscle mass. Muscle will also benefit your overall body composition; body composition is how much fat-free mass (fat-free mass refers primarily to muscle mass) you carry in ratio to the fat mass you carry on your body(21). Two people can weigh the same but have different body compositions.
If you can talk during your cardio, you are in zone 2. But you can accomplish fat burn with zone 2 training, strength training, and HIIT. Using zone 2 as a guide is great, but do not neglect other energy systems, use a variety of intensities in your workouts. Practically all physical activity, regardless of zone, will benefit your health in some way. However, from a longevity standpoint, zone 2 provides specific benefits linked to how your body produces energy during this type of exercise. Going on a 20-minute walk three times a week will be a great lifestyle habit.
Having an overall healthy workout regimen for yourself and your lifestyle is easy; listen to your body and think about all the benefits you get from moving that incredible body of yours. Your body is meant to move. Zone 2 training is excellent, but try some strength training and HIIT when you are ready. You got this.
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