Forget guesswork. By understanding these five heart rate zones, you can optimize every workout and experience maximum results.

In the lower heart rate zones—typically defined as zones 1 and 2, and sometimes even up into zone 3—you’re helping your body recover from harder efforts, strengthening type I muscle fibers ...

Your heart rate should stay within 60 to 70 percent of its maximum while you train in this zone. It's a simple concept at first glance, but it is incredibly effective at building your endurance.

Zone 3 (75-85% of max heart rate): At this moderate to high intensity, your body burns a mix of fat, carbohydrates and protein for fuel. Talking requires effort, as your breathing is heavier.

Sometimes taking your fitness routine to the next level means slowing down. Experts explain the benefits of Zone 2 cardio, ...

In general, heart rate zone 2 matches power zones 2-3. But your heart rate drifts upward the longer you work out, and your heart rate also takes longer to change when you shift gears.