The Karvonen method is used to determine the Target Heart Rate (THR) for a given activity. This method is considered to be more accurate than other methods for measuring THR because it takes the Resting Heart Rate (RHR) into consideration. The basic formula is: Maximum Heart Rate - Resting Heart Rate = Heart Rate Reserve (HRR). The HRR is then used to find out THR for a given intensity of workout. Ideally for an aerobic activity to have any benefit the THR should be between 60% to 90% of the Maximum Heart Rate (MHR). The MHR is calculated by subtracting an individualâ€™s age from 220. The Karvonen Method is useful in charting the progress of an individual during the course of an aerobic training program.