I am 43, in fairly good shape, exercise regularly (3-4 times a week) and have noticed for many years that my heart rate gets to 160's-170's during moderate exercise on cardio machines. I don't have any symptoms other than some shortness of breath but it feels normal. I am wondering if I should have a stress test to make sure there is nothing unusual about my heart rate when it gets this high. I have spoken to a doctor about this and he didn't think it was necessary if I am not symptomatic.