When I first started training for this ironman, I knew the importance of heart rate based training and never had so much of background with the amount of hours. It was starting to take kind of a toll on my body. I was getting some colds. I was getting sick fairly easily. I needed something that was going to give me more than just my first Polar that I purchased when I was back in college. So I got an RS800CX. Using the heart rate monitor, I was able to learn and to gauge when my body was starting to go into that overtraining phase, and then I could adjust my plans accordingly with the coach. The RS800cx was actually able to do my running and my cycling, which was huge.