Heart rate is highly individual. Conventional wisdom says subtract your age from 220 to get your max. You should train at levels below 85% of that. In my case, I can easily maintain a heart rate that is considerably higher than my calculated maximum. I have been stress tested three times and was able to maintain a heart rate over 200 with zero stress on my heart. The last time I ran for 25 minutes on an inclined treadmill at a maximum heart rate of 204 and my blood pressure never got higher than 130/90. I am 55 years old, so you can do the math. My cardiologist told me not to come back because he doesn't have any equipment that can stress my heart and he said I just have abnormal physiology. But that would not be a benchmark that others should attempt to duplicate.I know there are a lot of myths floating around about heart rate. I'm a 23 year old female. What should my heart rate be at during my cardio workouts?