Zone 2 is a popular name for steady aerobic work performed at a comfortable-but-purposeful intensity. Heart-rate systems use different formulas and zone boundaries, so there is no single beats-per-minute number that fits everyone. The practical target is an effort you can maintain for a while: breathing is elevated, but you can still speak in complete sentences without gasping.
Why it is useful
Steady work can improve aerobic fitness while creating less fatigue than frequent all-out intervals. Walking uphill, easy jogging, cycling, swimming, or rowing can all work. The best mode is one your joints tolerate and your schedule allows. Someone returning to exercise may find brisk walking appropriately demanding, while an experienced runner may need an easy run or bike ride to reach the same internal effort.
Start with two or three sessions of 20–30 minutes each week. Build duration before intensity. If you use a heart-rate monitor, treat the number as feedback rather than a command: heat, dehydration, caffeine, medication, illness, and sensor error can all change it. The talk test and perceived effort are valuable backups.
Pairing it with strength work
Cardio does not automatically “kill gains.” Problems usually come from excessive total fatigue, poor fuelling, or hard endurance sessions placed too close to demanding leg training. Put easier cardio after lifting or on separate days when possible, and keep truly hard intervals limited if strength or muscle gain is the priority. Increase one part of the plan at a time.
For general health, the unglamorous answer is often best: move frequently, choose an effort you enjoy enough to repeat, and progress slowly. Chest pain, fainting, unusual breathlessness, or a known cardiovascular condition require medical guidance before changing exercise intensity.