Think of it as a sustainable effort: “In Zone 2, you should feel comfortable,” like you could go for two hours or longer, Athena Farias, an exercise physiologist, certified personal trainer, and running coach at Get Fit SATX, in San Antonio, tells SELF. (Note: If you’re just getting started with exercise in general or running specifically, the idea of doing anything for hours can sound impossible. This really does mean slowing down a LOT—and also, it’s not something to obsess over right away, which we’ll get to in a moment.)
There are tons of health and performance benefits to zone 2 training.
Zone 2 workouts do indeed bring lots of perks, Dr. Olenick says—she’s even called them the “best-kept secret” of coaches and fitness pros. And their benefits all have to do with the way your cardiovascular and metabolic systems respond over time.
When you regularly exercise at that sustainable level, your muscles, heart, and lungs get comfortable working a bit harder and your body adapts to maximize these changes, Dr. Olenick says. Your heart will become stronger and more efficient at pumping blood through your body. You’ll sprout new capillaries, tiny blood vessels that carry oxygen-rich blood into your muscles. Inside those muscles, your mitochondria—the energy factories that turn oxygen into fuel—will become more plentiful and powerful.
As a result, you’ll build what’s called your aerobic or cardiovascular base, a reserve of fitness that helps you sustain each effort for longer. Thanks to a solid base, every subsequent workout, including ones that take you into higher zones, should feel easier, helping you get more work done more efficiently. In fact, one small study found doing two hours of low-intensity exercise per week improved recovery—and also boosted running performance—after about a month; another found benefits for recovery and endurance when pro soccer players incorporated more lower-intensity training. And you’ll also see several health benefits from these chill sessions, such as a lower risk for insulin resistance and diabetes, heart disease, and stroke, Farias says.
Now, you can reap most of these rewards from any type of aerobic exercise. But the huge benefit of zone 2 is that you can do so without majorly taxing your body, something that can’t be said for high-intensity intervals, Dr. Olenick says. Because zone 2 doesn’t cause a lot of fatigue, you can rack up a lot of hours or miles of these easier efforts each week without less risk of overdoing it (though you should still gradually build up the amount of time you’re working out).
There’s also a psychological benefit to this type of training. You might feel a sense of bliss or a runner’s high, almost like you’re floating. If you’re exercising outside, you can take time to pay attention to the flowers blooming or the trees changing colors (since after all, you’re not busy worrying about the fact that you can’t breathe or your heart might explode). “Zone 2 is soul fuel,” Farias says. “This is your time to have a conversation with your friend or your spouse, enjoy nature, whatever you need to do to decompress.”
But zone 2 training can also stress the hell out of you.
Sometimes, though, this kind of training becomes less about simply moving your body in a chill way and more about making sure you’re hitting your “easy” numbers. One of the biggest frustrations? When doing just about any type of cardio takes your heart rate too high and out of that golden zone, Dr. Olenick says—even, sometimes, if you feel like you’re trying to keep it easy. That’s especially true if you’re new to fitness, or coming back to a routine after some time away.