What is the formula used to determine the target heart rate (THR)?

The formula to determine the target heart rate (THR) involves understanding the individual's maximum heart rate (MHR), resting heart rate (RHR), and the desired exercise intensity (I). The correct formula, THR = I x (MHR - RHR) + RHR, is derived from the Karvonen method, which takes into account the individual's heart rate reserve (the difference between MHR and RHR).

This formula allows for a more personalized approach by factoring in how hard an individual should exercise based on their fitness level and resting heart rate. By multiplying the desired intensity (expressed as a decimal) by the heart rate reserve, and then adding the resting heart rate back in, this equation effectively determines a target heart rate that aligns with the person’s fitness goals.

Using this method is crucial for safely achieving the right level of exertion, promoting cardiovascular fitness, and ensuring that the heart doesn't exceed safe limits during exercise. The other formulas do not take into account the resting heart rate and changes in exercise intensity, making them less suitable for determining an efficient and safe target heart rate.