Zone 2 cardio refers to low-to-moderate intensity aerobic exercise performed at a heart rate where your body primarily burns fat for fuel. Zone 2 cardio builds the aerobic foundation necessary for a long, healthy life—without overloading your body. It’s part of a 5-zone system used to measure exercise intensity based on heart rate and oxygen consumption.
Zone 2 is often referred to as the “fat-burning zone” because it maximizes the use of fat as a fuel source while keeping effort sustainable.
In Zone 2, you’re training at 60–70% of your max heart rate. You can hold a conversation, your breathing is steady, and it feels sustainable for long periods—think fast walking, slow running, cycling, or rowing.
Zone 2 training increases mitochondrial density, enabling your muscles to burn more fat for energy at rest and during exercise (Holloszy & Booth, 1976).
Mitochondria are your body’s energy factories. Zone 2 promotes mitochondrial biogenesis, improving endurance and delaying age-related decline (Lanza et al., 2008).
VO₂ max—a key predictor of longevity—improves with consistent aerobic training. Even moderate increases reduce the risk of cardiovascular and all-cause mortality (Kodama et al., 2009).
The ‘interference effect’ is so overblown. Cardio is mandatory for heart health.
I’m a powerlifter and I’ve been using this to stay in my weight class. It works.
Great content. How would you adjust this for a 4-day split?