While participating in the P90x program, I needed to find a watch that would accurately calculate my heart rate. After doing much research and comparison shopping, I decided to purchase this watch from Reebok. I have to say I'm very surprised at the negative feedback. I have not had any problems with the calculations of the calories burned, heart rate estimation or any other element. In fact, I LOVE the variety of features this watch offers. I also appreciate the design, so many other similar products are too bulky and garish. This watch is sleek and stylish and has become part of my daily attire.