The best tips to keep you in the zone.

Meredith Dietz

Meredith Dietz Senior Staff Writer

Experience

Meredith is a marathon runner and stand-up comedian. As Lifehacker’s Senior Staff Writer, she covers personal fitness tech, home gym equipment, and more.

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November 6, 2026

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Credit: René Ramos/Lifehacker/Getty Images

If you've spent any time in or around running culture over the last few years, you've undoubtedly encountered someone preaching the gospel of Zone 2 cardio. Legend has it that easy, conversational effort cardio—also known as cardio that takes your heart rate into "Zone 2"—is the secret to unlocking everything from a bigger aerobic engine to faster race times and even a longer life .

To train by heart rate, you aim to keep your heart rate in the "zone" that gives you the desired workout. The catch is that Zone 2 is easy to get wrong, especially since no one can agree on what it actually means .…