I bought an HRM from sharper image today and decided to test it out on my HIIT session. It said I burned 500 calories after 32 minutes. This seems awfully high to me. It also said I was working between 85 to 99 percent of my heart rate, which I'm not sure is accurate. My hr was up to 190 at one point and I felt quite faint so I lowered the intensity, but other than that, I didn't feel too bad. How does one know their actual max heart rate? I think that might be why the numbers are so high... Does anyone have experience with these things? Oh, and if it helps to know, my hrm includes a chest strap.