What is the formula in getting the highest of PMHR and lowest of THR?

To find the highest of the predicted maximum heart rate (PMHR), you can use the formula: PMHR = 220 - age. For the lowest target heart rate (THR), a common method is to calculate 50% of your PMHR. Therefore, the highest PMHR is determined by your age, while the lowest THR is derived by taking 50% of that PMHR value.