2. If you have a serious illness (diseases that affect exercise, such as heart disease and high blood pressure) or just recovered (just recovered from illness or just discharged from hospital), subtract 103. If you are a beginner who has never exercised or only exercised intermittently (in the last two years), or have a cold more than twice a year, or have allergies, subtract 54. If you exercise at least four times a week for more than two years, you won't get hurt during exercise. A 30-year-old person doesn't have a 2-4 situation, which belongs to beginner 3, that is, 180-30-5= 145, which is the maximum heart rate you train with MAF. After getting the maximum heart rate, the most important thing is to keep the heart rate in the range of-10 during training. Take the 30-year-old as an example, the heart rate should be kept within the range of 135- 145, as close as possible to 145. I hope this helps.