Workouts don’t have to be so hard. Here’s how low-intensity training transforms your body.
Low-intensity Zone 2 workouts may sound simple, but they can improve metabolic health, help regulate blood sugar, and enhance endurance in the long term.
Aerobic exercises, such as running, jumping rope, and swimming, often get lauded for their role in warding off chronic illnesses like high blood pressure, heart disease, and Type 2 diabetes—not to mention their mental health perks. But there’s a common misconception: the more intense the exercise, the better the benefits.
Recent research shows that low-to-moderate intensity exercise, such as Zone 2 training, may be just as—or even more—effective for improving health and endurance. Think of a steady walk, a relaxed jog, or cycling at a sustainable pace.
This approach can help improve “metabolic flexibility,” or the body’s ability to seamlessly switch between fats and sugars for energy. Metabolic inflexibility is often associated with chronic conditions such as type 2 diabetes. It can make managing these conditions harder, as the body is forced to over-rely on sugars for fuel.
Here’s how this gentle yet effective approach to fitness benefits the body on multiple levels, from mitochondrial health to sustained energy.
Why Zone 2 is a fat-burning powerhouse
Exercise intensity is often broken down into five separate heart rate zones, each representing a different percentage of your maximum heart rate. Zone 2, which falls between 60 to 70 percent of a person’s maximum heart rate, is “your all-day pace,” says Brady Holmer, an exercise scientist and the author of the newsletter Physiologically Speaking. “Theoretically, it’s at such a low intensity that you can keep going and going.” This low-to-moderate intensity training can include activities like a steady walk, a relaxed jog, or cycling at a pace you could maintain for hours.
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One easy way to know if you’re in Zone 2? Try the “talk test.” “You should be able to carry out a conversation without any abnormal breaths,” says Hunter Waldman, an exercise scientist at the University of North Alabama.
Studies show that training your body to be more metabolically flexible can enhance the body’s ability to rely on fat as a predominant energy source, leading to improved endurance and increased efficiency at low to medium exercise intensities.
“You’re making the body more dynamic to deal with the situation at hand,” says Travis Nemkov, an exercise scientist at the University of Colorado Anschutz Medical Campus.
This kind of exercise also offers a unique physiological advantage: it’s just below the lactate threshold, the point where lactate—an essential energy source—builds up in the blood faster than it can be removed. As exercise intensity increases beyond Zone 2, the body’s energy demands shift to favor a lactate-producing metabolism (glycolysis) over a lactate-consuming metabolism. At these higher intensities, carbohydrate use increases as a rapid fuel source while fat burning slows down.
What are the benefits of Zone 2 training?
For people with conditions like type 2 diabetes, which makes regulating blood sugar levels challenging, Zone 2 exercises can help blood sugar regulation by providing an alternative pathway for lowering glucose levels. “Skeletal muscle is capable of taking up glucose in an insulin-independent fashion, and exercise is a driver of that,” Nemkov says.
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Having that metabolic flexibility can translate to a competitive advantage for endurance athletes, as fat is more readily available as an energy source than sugars. “If you are able to use fat as an energy source when you are exercising, you are going to reduce your reliance on glycogen stores,” which are available in more limited amounts in the body, Holmer says, adding that “you are going to feel better exercising and you might not have to fuel as much.”
For example, a recent study showed that professional cyclists who were better able to use fat for energy had a competitive advantage over their peers who didn’t use fat quite as effectively. It also improves endurance by increasing the body’s ability to use aerobic metabolism, which is more efficient, for longer periods of exercise.
For people just starting a fitness routine, Zone 2 training has some additional benefits, the major one being that it is sustainable. Zone 2 training can be done at a moderate pace, leaving a person feeling better the next day and ready to go again. In contrast, over-reliance on high-intensity training can lead to quicker burnout and longer recovery times. “Exercise doesn’t have to hurt,” Holmer says.
