According to the equation provided by HPMC Occupational Medical Services, the target heart rate during aerobic exercise for a 49-year-old adult should be between 111 and 145 beats per minute. At this rate, the heart works at 65 to 85 percent of its maximum capacity.
To calculate a person's target heart rate zone, HPMC offers a simplified series of steps to follow. First, determine a person's maximum heart rate by subtracting his age from 220. Next, multiply the maximum heart rate by the desired target heart rate percentage. For example, if a 35-year-old wants to know his target heart rate at 75 percent, he subtracts 35 from 220. Next, he multiplies the result, 185, by 75 percent or 0.75. At 75 percent usage, his target heart rate is approximately 139 beats per minute.