Zone 2, the easy cardio you can talk through

Zone 2 is steady cardio at an effort where you can still hold a conversation. For most people that's a brisk walk uphill, an easy jog or a relaxed bike ride. In a lab it's the effort just below the point where lactate starts building up in your blood. Outside a lab, heart rate is the usual stand-in.

The case for moderate cardio is strong. The WHO recommends 150 to 300 minutes a week for adults. A pooled analysis of 661,137 adults found that people who met the 150-minute minimum were 31% less likely to die over 14 years than people who did no exercise in their free time. Doing three to five times that much raised the figure to 39%. The first 150 minutes do most of the work.

The case for zone 2 in particular is weaker. Its popularity comes from elite endurance athletes, who train huge volumes at that intensity. A 2025 review found no evidence that zone 2 beats harder exercise for fitness or for your mitochondria. With only a few hours a week, harder sessions seem to give more fitness per minute. Zone 2 is still a good base because it's easy to recover from and easy to stick with. Add some harder efforts if you can.

Ageon counts a zone 2 day when your watch records at least 20 minutes of workouts at 60 to 70% of your maximum heart rate. It estimates your maximum as 208 minus 0.7 times your age, a formula from a study of over 18,000 people. Your real maximum may differ.

A zone 2 day earns 3 points, the most a habit can earn, because it's moderate cardio and the evidence for moderate cardio is strong. This article is tagged moderate because the evidence that zone 2 beats other cardio isn't.