The maximum heart rate is the highest heart rate achieved during maximal exercise. In general, you get the most benefits and reduce the risks when you exercise within your target heart rate zone. Usually this is when your exercise heart rate (pulse) is about 80 percent of your maximum heart rate. The formula M = 0.8 ( 220 − A ) M = 0.8 ( 220 - A ) , gives the recommended maximum heart rate, M M , in beats per minute, for a person who is A A years of age. Determine the age of a person whose target heart rate is 128 beats per minute. The recommended maximum heart rate is 128 beats per minute for a person who is years old.