Peak heart rates (MHR - Max Heart Rate) is a measure of how many BPM (beats per minute) your heart can withstand before going into cardiac arrest. Theoretically calculated value for MHR is:
MHR = 220 - your age, thus, if you are 30, then 220 - 30 = 190bpm = your MHR.
This however, is as, I mentioned, THEORETICAL. It is completely possible to go past this with proper conditioning. Mine is calculated at 189 and I consistently exceed 195 for several minutes when I do cardio, even on restricted oxygen (nose plugged and wearing a dual mouthpiece). I've had it as high as 203.
Before I go any further, do you have some sort of goal in mind, such as fat loss, fight conditioning, etc.?