__Rule 1: Heart rate is an indicator of exercise__ Your heart rate tells you how hard you are working out. During moderate to vigorous exercise, your heart rate should be between 50 % and 85 % of your maximum heart rate. It is important to follow this rule to avoid overexerting your heart. __Rule 2: Your heart rate should not exceed the number you get when you subtract age from 220__ This is the highest rate at which your heart can beat ===during physical activity. If your heart rate has not yet reached its maximum value during exercise, but you already feel dizzy or cannot breathe or speak, this is a sign of severe overexertion. When your heart rate exceeds 90 % of your available maximum it can be dangerous for your heart. Increase the intensity gradually, which will make you more resilient. __Rule 3: Use a smartwatch to help you get in shape__ Smartwatches and electronic heart rate monitors with built-in heart rate sensors can help control your heart intensity and exercise level. They can also help you adjust your workout plan, avoid overexertion, and stay motivated. __Rule 4: Check your heart rate regularly__ If you have a heart problem or other medical condition, it's imperative that you monitor your heart rate. Even if you are healthy, try to monitor it every 5 to 10 minutes as you increase the intensity of your exercise. This will help you develop a workout plan that is safe and optimal for you. __Rule 5: Follow the heart rate formula for interval training__ Interval training consists of low- or moderate-intensity exercises that alternate with high-intensity ones. They are popular because they help quickly "dry out" the body and replace fat deposits with muscle mass as well as strengthen heart muscle and lower cholesterol and blood sugar levels. One way to figure out how to train during each interval is to monitor your heart rate. During periods of low to moderate exertion, your heart rate should be about half of your maximum possible heart rate. During intense exercise, your heart rate should be between 70-85 % of your maximum. __Rule 6: Maximum calorie burning occurs at a certain heart rate__ Calorie burning starts at a heart rate of 60-80 % of maximum. How prepared your body is for exercise is very important. The less trained a person is, the lower their fat-burning zone. The optimal heart rate for running and moderate aerobic activity is in the 60-70 % range.