Target Heart Rate

Exercising at different intensities yields different results. Heart rate zones help you target specific energy systems:

• Zone 2 (60-70%): The endurance foundation. You should be able to hold a conversation. Ideal for long, slow runs and fat oxidation.
• Zone 3 (70-80%): The "grey zone." Harder work, improves aerobic capacity and blood circulation.
• Zone 4 (80-90%): Anaerobic threshold. This is where your muscles start to burn. Improves speed and lactic acid tolerance.
• Zone 5 (90-100%): Maximum effort. Sustainable for only very short bursts (HIIT, sprints).

Most simple calculators just use 220 - Age to find your Max Heart Rate (MHR) and take percentages of that.

Why we use Karvonen: The Karvonen formula is more accurate because it factors in your Resting Heart Rate (RHR). It calculates your "Heart Rate Reserve" first, ensuring the training zones are personalized to your current fitness level.

You've likely seen "Fat Burn Zone" on cardio machines (Zone 2). It is true that at lower intensities, a higher percentage of calories burned comes from fat.

However, high-intensity workouts (Zone 4/5) burn significantly more total calories in less time. Don't fear the higher zones if weight loss is your goal—total calorie deficit is king.