Zone 2 Cardio vs HIIT: The Best Mix for Fat Loss, Fitness, and Stress Management

Zone 2 is an easy, steady effort where you can speak in full sentences. It’s roughly 60–70% of max heart rate, or RPE 3–4. Without gadgets, use the talk test; with a monitor, aim for a heart rate where breathing is deeper but controlled and you can maintain pace for 30–60 minutes.

For most, 4–12 total minutes of hard work weekly is sufficient. That could be 1 session of 8–12 x 30–45 seconds or 2 micro-sessions of 4–6 x 30 seconds. Add more only if sleep, mood, and performance stay solid for 2–3 weeks.

HIIT burns more calories per minute, but its higher fatigue can reduce non-exercise activity and increase appetite. Zone 2 allows more total weekly volume and steps. Over a week, either can support fat loss if diet is in a slight deficit; Zone 2 is often easier to sustain.

Keep heavy lifting and hard intervals on separate days or separate them by at least 6–8 hours. Avoid HIIT within 24 hours of heavy lower-body sessions. Zone 2 pairs well after upper-body lifts or on separate easy days.

Signs include poor sleep, irritability, elevated resting heart rate, lower HRV, heavy legs, and declining interval power. If these persist for 3–5 days, reduce HIIT volume, prioritize Zone 2 and steps, and revisit nutrition and sleep.